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TO COMPARE THE CREATININE CLEARANCE IN 12 HOUR AND 24
HOUR TIMED URINE COLLECTION IN HEALTHY VOLUNTEER
BY
RAJ KUMAR YADAV
A DISSERTATION SUBMITTED TO THE RAJIV GANDHI UNIVERSITY OF
HEALTH SCIENCES, KARNATAKA, BANGALORE
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE
OF
MSc. MLT (BIOCHEMISTRY)
DEPARTMENT OF BIOCHEMISTRY,
ST. JOHN’S MEDICAL COLLEGE AND HOSPITAL,
ST. JOHN’S NATIONAL ACADEMY OF HEALTH SCIENCES, BANGALORE,
KARNATAKA, INDIA.
2007 - 2009
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ST. JOHN’S MEDICAL COLLEGE
BANGALORE – 560034
Ph (080) 22065050 Telegrams:
“SAINJOHNS”
DECLARATION
This is to declare that this dissertation entitled ‘To Compare The Creatinine Clearance
In 12 Hour And 24 Hour Timed Urine Collection In Healthy Volunteer’ has been
prepared by me under the guidance and direct supervision of Dr. Anitha Devanath,
Associate Professor, Dept of Biochemistry, St. John’s Medical College. This dissertation
is submitted in partial fulfillment of the regulations of Rajiv Gandhi University of Health
Sciences and has not formed the basis of a degree or diploma to me by any other
university before.
I hereby declare that the Rajiv Gandhi University of Health Sciences, Karnataka shall
have the rights to preserve, use and disseminate this dissertation in print or electronic
format for academic / research purpose.
Date: 28th
April 2009 Mr. Raj Kumar Yadav
Place: Bangalore MSc MLT student (Biochemistry)SJMC, Bangalore
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Ph (080) 22065050 Telegrams:
“SAINJOHNS”
CERTIFICATE
This is to certify that the study entitled ‘To Compare The Creatinine Clearance In 12
Hour And 24 Hour Timed Urine Collection In Healthy Volunteer’ is the bonafide
work of Mr. Raj Kumar Yadav, BSc MLT, and was carried out under the guidance and
supervision of Dr. Anitha Devanath, Associate Professor, Dept of Biochemistry, St.
John’s Medical College, Bangalore, in partial fulfillment of the regulations for the degree
MSc. MLT (Biochemistry).
Date: 28th
April 2009 Dr. Sultana FurruqhPlace: Bangalore MD
Professor and Head,
Department of BiochemistrySJMC, Bangalore
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Ph (080) 22065050 Telegrams:
“SAINJOHNS”
CERTIFICATE
This is to certify that the study entitled ‘To Compare The Creatinine Clearance In 12
Hour And 24 Hour Timed Urine Collection In Healthy Volunteer’ is the bonafide
work of Mr. Raj Kumar Yadav, BSc MLT, and was carried out under the guidance and
supervision of Dr. Anitha Devanath, Associate Professor, Dept of Biochemistry, St.
John’s Medical College, Bangalore, in partial fulfillment of the regulations for the degree
MSc. MLT (Biochemistry).
Date: 28th
April 2009 Dr. Prem Pais,
Place: Bangalore MD
Dean,
SJMC, Bangalore
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ST. JOHN’S MEDICAL COLLEGE
BANGALORE – 560034
Ph (080) 22065050 Telegrams: “SAINJOHNS”
Declaration by the candidate
I hereby declare that the Rajiv Gandhi University of Health Sciences,
Karnataka shall have the rights to preserve, use and disseminate this dissertation in print
or electronic format for academic / research purpose.
Date: Mr.Raj kumar yadav.
Place: Bangalore MSc. MLT student (Biochemistry)
SJMC, Bangalore.
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ACKNOWLEDGEMENT
I am thankful to Rev. Fr. Lawrence D’souza, Director, St. John’s National Academy of
Health Sciences, Dr. Prem Pais, Dean, Dr. Karuna Rameshkumar, Vice Dean & the
course Co – Ordinator, St. John’s Medical College for giving me the opportunity to
pursue my postgraduate studies.
I wish to thank Dr. Sultana Furruqh, Professor and Head, Department of Biochemistry,
for all the help and encouragement given to me while conducting this study.
I am ever grateful to Dr. Anitha Devanath, Associate Professor, Department of
Biochemistry for the immense help, guidance and support regarding this dissertation
work.
I am thankful to all the teaching and non- teaching staff of the Department of
Biochemistry for their help, assistance and co-operation.
I thank my colleagues for their valuable support and help. I thank all the subjects who
consented for this study, without whom, conducting this study would not have been
possible.
Date: 28th
April 2009 Mr.Raj Kumar Yadav
Place: Bangalore MSc. MLT student,SJMC.
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Abstract
Introduction: The kidneys remove creatinine, which is produced at a constant rate as a
result of muscle metabolism, from the blood. Like inulin, creatinine is filtered, but neither
reabsorbed nor secreted by the kidneys. Thus, the creatinine clearance test, which
compares a patient's blood and urine creatinine concentrations, can also be used to
calculate the GFR. A significant advantage is that the bloodstream normally has a
constant level of creatinine. Therefore, a single measurement of plasma creatinine levels
provides a rough index of kidney function.
Aims and Objectives: To compare the Creatinine clearance in 12-hour and
24-hour timed urine collection in healthy volunteer.
Materials and Methods: 50 Healthy volunteers are selected based on criteria. Out of
these, 25 volunteers will be female and 25 volunteers will be male. Each volunteer will
be given 2 cans for urine collection. Urine collection will begin at 7 am in the morning on
day 1 till 7 am on day 2 (next day); The first can is used for collection from 7 am to 7 pm
on day 1. The second can will be used for another 12 hour collection study from 7pm on
day 1 to 7am on day 2. Mix well and measure the volume separately in both the can. Take
5ml of sample from the first can; labeled it as sample1. Then mix both the contents of the
can by transferring from can 1 to can 2 .Mix well and take another 5ml of sample; labeled
it as sample 2. Sample1will pertain to 12-hour turned urine collection. Sample 2 will
pertain to 24-hour turned urine collection. The creatinine is measured by using
modification of the kinetic Jaffe reaction.
Result: The pearson’s correlation between 12-h and 24-h urine samples showed a
significant correlation in both males and females (r = 0.8 and 0.6 respectively, p values <
0.05)
Conclusion: This is clinical acceptable and hence 12 hr urine collection can be adopted
in patients who are well hydrated and it can replace 24-h urine collection
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TABLE OF CONTENTS
1.INTRODUCTION………………….…………………………………......................1
1.1 Inulin Clearance Test…………………………………………….…..…..……2
1.2 Urea Clearance Test………………………………………..…….…..………..3
1.3 Para-Aminoh ippu ric acid (PAH) Clear ance Test ………..……...... . .4
1.4Creatinine Clearance Test………………………………….……..…..5
1.5 Pitfalls with 24 hour Urine collection………………….……..……5
2. AIM AND OBJECTIVES……………………………………………………..……7
3. REVIEW OF LITERATURE…………………………………………………..…..8
3.1 Creatinine...........................................................................................…...8
3.2 Clinical Utility…………………………………………………………...….11
3.3 Markers used …………………………………………………………12
3.4 Creatinine in biological fluid ……………………………..….…..12
3.5 Cockcroft and Gault formula………………………….………...…19
3.6 MDRD Study equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
3.7 Factors that affect creatinine secretion. . . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . .23
3.8 Kidney………………………………………………………………..28
3.8.1 Anatomy…………………………………………………...28
3.8.2 Physiology………………………………………………...31
3.8.3 Function…………………………………………………...31
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3.8.4 Acute Renal Failure………………………………….…..34
3.8.5 Chronic Kidney Disease…………………………………41
4. MATERIALS AND METHODS…………………………………………………48
4.1Source Of Data……………………………………………………………48
4.2 Criteria……………………………………………………………………48
4.3 Method of Sample Collection……………………………………………48
4.4 Method of Creatinine Analysis………………………………………….49
4.5 Principle…………………………………………………………………..49
5. STASTICAL ANALYSIS………………………………………………..50
6. RESULT…………………………………………………………………………..50
7. TABLE……………………………………………………………………………51
8. DISCUSSION……………………………………………………………………53
9. C0NCLUSION…………………………………………………………………..54
10.REFERENCE…………………………………………………………………..55
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ABBREVIATION
GFR : Glomerular Filtration Rate
ml : milli liter
min : minute
CKD : Chronic Kidney Disease
CVD : Chronic Vascular Disease.
PAH : Para-aminohippuric acid.
EDTA : Ethlenediaminetetraacetic acid
DTPA : Diethylenetriaminepentacetic acid
PECT : plasma exogenous creatinine clearance test
NKDEP : National Kidney Disease Education Programme
ADH : Anti-Diuretic Hormone
ARF : Acute Renal Failure
ATN : Acute Tubular Necrosis
ACE : Agiotensin Converting Enzyme
ASN : American Society Of Nephrology
CCr : Creatinine Clearance
CrC l : Creatinine Clearance
SCr : Serum Creatinine
ESRD : End Stage Renal Disease
NSAID : Non-Steroidal Anti-Inflammatory Drug
RIFLE :
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1. INTRODUCTON
GFR is usually accepted as the best overall index of kidney function in health and disease.
Normal GFR varies according to age, sex, and body size; in young adults it is approximately
120-130 mL/min/1.73 m2 and declines with age. A decrease in GFR precedes the onset of
kidney failure; therefore a persistently reduced GFR is a specific diagnostic criterion for
CKD. Below 60 mL/min/1.73 m2, the prevalence of complications of CKD increases, as
does the risk of cardiovascular disease.
Kidney function is proportional to kidney size, which is proportional to body surface area. A
body surface area of 1.73 m2 is the normal mean value for young adults. Adjustment for
body surface area is necessary when comparing a patient’s estimated GFR to normal values
or to the levels defining the stages of CKD.
The GFR declines with age. Although the age-related decline in GFR has been considered
part of normal aging, decreased GFR in the elderly is an independent predictor of adverse
outcomes such as death and CVD. In addition, decreased GFR in the elderly requires
adjustment in drug dosages, as in other patients with CKD.
GFR cannot be measured directly. The urinary clearance of an ideal filtration marker, such
as inulin, iothalamate or iohexol, is the gold standard for the measurement of GFR. This is
cumbersome in clinical practice and serum levels of endogenous filtration markers, such as
creatinine, have traditionally been used to estimate GFR.
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Renal clearance is defined as the rate at which a particular chemical is removed from the
plasma and it indicates kidney efficiency. Tests of renal clearance can detect glomerular
damage or judge the progress of renal disease.
The renal clearance tests available for measurement of Glomerular Filtration Rate (GFR)
are: Inulin Clearance Test, Urea Clearance Test, Para aminohippuric acid test and Creatinine
Clearance Test.
1.1 Inulin Clearance Test:
Inulin, a complex polysaccharide found in certain plant roots. 100ml of sterile 10% solution
of inulin is given up as slow intravenous drip within 2 hours. Urine specimen formed during
this period is collected totally. Blood sample is taken at the middle of the test. Inulin is
estimated by resorcinol giving a red colour. The test needs continuous infusion of inulin so
as to keep the plasma level adequate.
The inulin passes freely through the glomerular membranes, so that its concentration in the
glomerular filtrate equals that of the plasma. In the renal tubule, inulin is not reabsorbed to
any significant degree, nor is it secreted. Consequently, the rate at which it appears in the
urine can be used to calculate the rate of glomerular filtration. The value of GFR as
measured by inulin clearance is 125ml/min . Inulin is estimated by resorcinol giving a red
colour. The test needs continuous infusion of inulin so as to keep the plasma level adequate.
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The advantage of Inulin clearance test is that Inulin is neither absorbed nor secreted by the
tubules. It is not metabolized by the body. The disadvantage is it involves administration of
an extraneous compound (Inulin).
1.2 Urea Clearance Test:
Urea is the end product of protein metabolism .The urea clearance is less then GFR, because
urea is partially reabsorbed. Urea clearance is the measure of ml of blood that contains the
urea excreted in a minute by the kidneys.
Allow the patient to have a normal breakfast. On day 1, at 9 AM give a cup of water and the
patient is instructed to void the bladder and the urine is discarded. Start collecting the urine
until day 2. At 10 AM bladder is completely emptied into the 24-hour urine collection. The
volume of urine is measured and the urine urea is estimated. A blood sample is taken to
estimate blood urea. The urea clearance is calculated by the formula
U x V
P
Where U = mg of urea per 100 ml of urine
P = mg of urea per 100 ml of plasma
V = ml of urine excreted per minute or (total volume / 24h x 60 min)
This is called the maximum urea clearance and the reference value is 75ml/minute when
urine flow rate is > 2 ml / min1
.
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The disadvantage of urea clearance test is that urea is normally reabsorbed from the renal
tubules and therefore tubular function also affects urea clearance2. Due to passive diffusion
across the tubular cells, urea is reabsorbed at low GFRs and measurements tend to
underestimate GFR. Consequently urea is now considered inadequate for measuring GFR.3,4
1.3 Para-aminohippuric acid (PAH) Clearance Test:
PAH, a substance that filters freely through the glomerular membranes. However, unlike
inulin, any PAH remaining in the peritubular capillary plasma after filtration is secreted into
the proximal convoluted tubules. Therefore, essentially all PAH passing through the kidneys
appears in the urine. For this reason, the rate of PAH clearance can be used to calculate the
rate of plasma flow through the kidneys. Then, if the hematocrit is known, the rate of total
blood flow through the kidneys can be calculated.
1.4 Creatinine Clearance Test:
The kidneys remove creatinine, which is produced at a constant rate as a result of muscle
metabolism, from the blood. Like inulin, creatinine is filtered, but neither reabsorbed nor
secreted by the kidneys. Thus, the creatinine clearance test, which compares a patient's
blood and urine creatinine concentrations, can also be used to calculate the GFR. A
significant advantage is that the bloodstream normally has a constant level of creatinine.
Therefore, a single measurement of plasma creatinine levels provides a rough index of
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kidney function. For example, significantly elevated plasma creatinine levels suggest that
GFR is greatly reduced. Because nearly all of the creatinine the kidneys filter normally
appears in the urine, a change in the rate of creatinine excretion may reflect a renal disorder.
For creatinine clearance, 24-hour urine sample has to be collected and an associated blood
sample is taken to estimate the creatinine levels. The procedure remains the same while
there are many formulas available for calculating the Creatinine Clearance.
Creatinine clearance approximates GFR but overestimates it due to the fact that creatinine is
secreted by the proximal tubule as well as filtered by the glomerulus. Creatinine clearance
can be measured from serum creatinine and creatinine excretion or estimated from serum
creatinine using estimating equations. Measurement of creatinine clearance requires
collection of a timed urine sample, which is inconvenient and frequently inaccurate.
Repeated measurements of creatinine clearance may overcome some of the errors.
1.5 Pitfalls with 24 hour Urine collection
Inaccurate and inconvenient
Sample has to be refrigerated during collection
Risk of Contamination, if procedure is not followed.
Cumbersome procedure
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6
Since 24-hour urine collection was found to be inconvenient and cumbersome, I investigated
further to see if 12hour timed urine sample collection could replace the 24-hour timed urine
collection.
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2.AIMS AND OBJECTIVES
• To compare the Creatinine clearance in 12-hour and 24-hour timed
urine collection in healthy volunteer.
• To assess whether 12-hour urine collection can replace 24-hour urine
collection
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3.REVIEW OF LITERATURE
3.1 Creatinine
Creatinine is the metabolic product of creatine and phosphocreatine, found exclusively in
muscle. It is formed in muscle from creatine phosphate by irreversible, non-enzymatic
dehydration and loss of phosphate. Creatinine production to muscle mass varies little from
day to day5. Creatinine, molecular weight of 113 Daltons does not bind to plasma proteins. It
is freely filtered by renal glomerulus6. Creatinine is excreted not only by glomerular
filtration but also by the renal tubule secretion. The secretion of creatinine varies
substantially7,8.
In addition, the proportion of total renal creatinine excretion due to tubular
secretion increases with decreasing kidney function9.
Synthesis of Creatinine:
Creatine is synthesized in the kidney, Liver and pancreas by two sequential enzymatically-
mediated reaction but synthesis occurs primarily in the liver. It is synthesized from Arginine,
Glycine, and Methionine. The two sequential enzymatic reactions are transamidation and
methylation. In transamidation reaction, Arginine and Glycine form guanidinoacetic acid.
In the methylation reaction, guaidinoacetic acid is methylated to form creatine. S-
adenosylmethionine acts as the methyl donors. Creatine is transported in blood to other
organ such as muscles and brain, where it is phosphorylated to phosphocreatine, a high
energy compounds.
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Interconversion of phosphocreatine and creatine is a particular feature of metabolic
processes of muscle contraction. A proportion of the free creatine in muscle (~1% to 2%/
day) spontaneously and irreversibly converts to creatinine, its anhydride. Thus the amount of
creatinine produced each day is related to the muscle mass (and body weight) and does not
vary greatly from day to day. The level of creatinine in the bloodstream is fairly constant,
although diet may influence the value, depending on the individual’s meat intake (by about
10%). The free creatinine is a waste product of creatine, is present in all body fluids and
secretions, and is freely filtered by the glomerulus. Although creatinine is not reabsorbed to
any great extent by the renal tubules, there is a small but significant amount of creatinine
secreted that increases with increasing levels of plasma creatinine. Creatinine production
also decreases as the circulating level of creatinine increases; several mechanism for this
have been proposed, including feedback inhibition of production of creatine, reconversion of
creatinine to creatine, and conversion to other metabolites10,11,12
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Figure 1: Creatine Synthesis from the Amino Acids: Arginine, Glycine and Methionine
Creatinine is released into the circulation at a relatively constant rate that has bean shown to
be proportional to an individual muscle mass. It is removed from the circulation by
glomerular filteration and excreted in urine. Additional amount of creatinine are secreted by
the proximal tubule. Small amount may also be reabsorbed by the renal tubules.13
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The amount of creatinine in the blood stream is reasonable stable,although the protein
content of the diet does influence the plasma concentration because of the observed
constancy of endogeneous roduction, detrmination of creatinine excretion has been used to
measure of the completeness of 24 hour urine collection in a given individual.
Creatinine is water soluble, it is present in small concentrations in sweat (0.1-1.3 mg/dl).
Creatinine also has been detected in peritoneal fluid, synovial fluid, bronchoalveolar lavage
fluid, and aqueous and vitreous humor.
14
Research in the 1950s and 1960s discovered small
quantities of creatinine in the vomitus and feces of uremic human beings.15
3.2 Clinical Utility:
The most widely used endogenous marker of GFR is measurement of serum creatinine or
creatinine clearance . The use of creatinine as a marker of GFR was developed in 1962 by
Rehberg,16
who used exogeneously administrated creatinine. This led to the work of Popper
and Mandel,17
who in 1937 developed the use of endogenous creatinine clearance. This has
been extremely popular in clinical medicine despite formidable difficulties associated with
its quantification and interpretation.18
The main patho-physiological difficulties include
variations in the rates of generation and secretion of creatinine by the renal tubules.19
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3.3 Markers used:
Exogeneous marker:
The use of exogeneous markers to measure GFR is recommended for the monitoring of
slowly progressing nephropathes such as that associated with diabetes. Exogeneous markers
are also used to determine a GFR that is used to set a benchmark against which to monitor
deterioration in GFR using an exogeneous molecules does enable smaller deteriorations in
renal function to be observed even when the imprescision in measurement is taken into
account.
Measurement of GFR, on the basis of either urinary clearance or plasma clearance of the
isotope, can be reliably undertaken using the radiopharmaceuticals51
Cr-
ethlenediaminetetraacetic acid (EDTA),20,21,22
125 I-iothalamate, and 99m Tc –
diethylenetriaminepentaacetic acid (DTPA) as exogeneous markers. Nonradioactive
compounds used as exogeneous markers to measure GFR include iOhexol,inulin,
iodoacetate, and diethylenetriaminepentacetic acid (DTPA).
Endogenous marker:
Example of endogenous marker include creatinine, urea and low- molecular-weight protiens
( e.g., cystatin C ). Endogenous molecules are advantageous in that no injection is required
and only a single blood sample is needed, which enormously simplifies the procedure for the
patient, clinical, and laboratory.
3.4 Creatinine in biological fluid:- Creatine constitutes only a small fraction of the total
nonprotien nitrogen of plasma and urine. It is unstable at both alkaline and acidic pH and
rapidly undergoes conversion to creatinine. Creatine in urine is usually measured as the
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Accurate determination of GFR using endogenous creatinine clearance in clinical practice is
beset with a number of problems. These problems relate to the difficulty in sample
collection, performance of the test, inconvenience to patients, waste of work time, and use
and cost of concomitant drugs. In addition, incomplete urine collection sometimes result in
imprecise estimation of GFR.26
Other more accurate modalities for assessing GFR are either
unavailable or very expensive and beyond the reach of most patients particularly in the
developing world.
Elevated creatinine concentration is associated with abnormal renal function, especially as it
relates to glomerular function .
The glomerular filteration (GFR) is the volume of plasma filterated(V) by the glomerulus
per unit of time(t).
GFR = V/t 1
Assuming a substance S, can be measured and is freely filtered at the glomerulus and neither
secreted nor reabsorbed by the tubule, the volume of plasma filtered would be equal to the
mass of the S filtered( MS ) divided by the plasma concentration( Ps).
V = MS / PS 2
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The mass of S filtered is equal to the products of its urine concentration(U S) and urine
volume VU .
MS = USVU 3
If the urine and plasma concentration of S,The volume of urine collected and the time over
which the sample was collected are known, the GFR can be calculated.
GFR = USVU/ PSt 4
an increasing muscle mass from conditioning or exercise will result in an increase of
phosphocreatine and serum creatinine. Males often have higher creatinine values than
females, as well.27
A small amount of creatinine is reabsorbed by the tubules and a small quantity of creatinine
that appears in the urine ( 7-10%) is due to tubular secretion.28
As the GFR falls, the plasma
creatinine rises disproportionately and the creatinine clearance can reach twice that of inulin.
.
Serum or plasma creatinine can be measured more accurately and reproducibly and, despite
many confounding factors, can be used to predict the creatinine clearance(GFR) using one
of several algorithms.
The serum creatinine concentration can vary based on a number of factors including an diet,
muscle mass, and gender. Diets that contain high concentrations of muscle offer a large pool
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of creatine and creatinine that are absorbed in the small intestine and contribute to the serum
concentration of creatinine. Muscle mass harbors the precursor of creatinine,
phosphocreatine , as an energy source. This compound is often mistakenly referred to as
"phosphocreatinine." A constant amount of phosphocreatine is spontaneously, irreversibly
and nonenzymatically converted to creatinine daily and utilized by the body. This amount is
directly proportional to the individual’s muscle mass. Therefore, a stable amount of
creatinine is presented to the kidneys daily for excretion. Muscle disease or wasting
decreases the amount of phosphocreatine available for conversion and thereby decreases the
serum creatinine concentration. Conversely, an increasing muscle mass from conditioning or
exercise will result in an increase of phosphocreatine and serum creatinine. Males often have
higher creatinine values than females, as well.29
This finding is most likely due to their
typically increased muscle mass as compared to females.
creatinine is water soluble, it is present in small concentrations in sweat (0.1-1.3 mg/dl).
Creatinine also has been detected in peritoneal fluid, synovial fluid, bronchoalveolar lavage
fluid, and aqueous and vitreous humor.30
Research in the 1950s and 1960s discovered small
quantities of creatinine in the vomitus and feces of uremic human beings
Serum creatinine values also depend on the kidney’s ability to excrete creatinine. An
elevation in creatinine is called azotemia and usually occurs simultaneously with an increase
in blood urea nitrogen, a compound that is also freely filtered by the glomerulus. This can be
due to prerenal, renal or postrenal processes causing a decrease in GFR. Examples of
prerenal processes that could cause azotemia include dehydration and some medications,
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such as gentamicin, oxytetracycline, amphotericin B, trimethoprim-sulfadiazine, and
furosemide.30
Renal processes could encompass anything from congenital or breed
abnormalities like Cocker Spaniel familial nephropathy or Greyhound glomerular
vasculopathy, to acquired renal failure from such causes as amyloidosis or intoxications by
sodium arsenate or vitamin D.30
Postrenal causes include urinary tract obstruction or rupture.
The endogenous creatinine clearance test is based on the principle that serum creatinine is a
constant value for that patient because of the irreversible nonenzymatic catabolism of
phosphocreatine from the muscle. Inaccuracies with this method are possible due to
incomplete evacuation of the bladder both before or after the procedure, tubular secretion of
creatinine in some male dogs, possible increased extrarenal secretion of creatinine (such as
in the gastrointestinal tract) and measurement of noncreatinine chromagens like ketones that
occur in the serum sample but not in the urine sample, as the chromagens are not present in
the urine. Patients that undergo this test usually are suspected of having renal disease
because they are polyuric, not azotemic.
The plasma exogenous creatinine clearance test (PECCT) is very similar to the iohexol
clearance test, currently considered the gold standard in human medicine. The PECCT is
useful for evaluating renal function in cases of known renal disease, detecting early renal
dysfunction in predisposed breeds, evaluation of GFR during or after certain drug protocols
that are nephrotoxic (like aminoglycoside therapy) and monitoring continued GFR failure in
cases of known renal failure.31
A pre-injection serum creatinine sample is collected, the
bladder emptied and an injection of creatinine is administered subcutaneously,
intramuscularly or intravenously. After a set period of time, 20 minutes to 24 hours, all of
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the urine created is collected and a post-injection serum creatinine value is determined. The
same calculation as described above is used to determine this value. This test is believed to
present an increased challenge to the kidney because of the presence of the exogenous
creatinine in addition to the endogenous creatinine concentration and is thought to better
represent the true GFR value. Also, with the increased amount of creatinine present, the
error from the presence of noncreatinine chromagens in the serum becomes less significant.
Serum and urine creatinine values measured over a 10 hour period give the practitioner the
most accurate picture of renal health, although reliable information can be gained with fewer
samples in a shorter time period, if desired. However, there is a lack of standardization of
methods between practioners that makes comparisons difficult. Also, it is unknown whether
some of the exogenous creatinine is shuttled to the proximal tubules and excreted there in
larger amounts as the kidney copes with the elevation in creatinine challenge.32
The National Kidney Disease Education Program (NKDEP) of the National Institute of
Diabetes, Digestive and Kidney Diseases (NIDDK), National Kidney Foundation (NKF) and
American Society of Nephrology (ASN) recommend estimating GFR from serum creatinine.
Two commonly used equations are the MDRD Study equation and Cockcroft and Gault
equation. Both equations use serum creatinine in combination with age, sex, weight or race
to estimate GFR and therefore improve upon several of the limitations with the use of serum
creatinine alone.
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3.5 Cockcroft and Gault formula:
The Cockcroft and Gault formula was developed in 1973 using data from 249 men with
creatinine clearance (CCr) from approximately 30 to 130 mL/m33
. It is not adjusted for
body surface area.
CCr={((140-age) x weight)/(72 SCr)} x 0.85 if female
where CCr is expressed in milliliters per minute, age in years, weight in kilograms, and
serum creatinine (SCr) in milligrams per deciliter.
4
3.6 MDRD Study equation:
The 4-variable MDRD Study equation was developed in 1999 using data from 1,628
patients with CKD with GFR from approximately 5 to 90 milliliters per minute per 1.73 m2.
It estimates GFR adjusted for body surface area and is more accurate than measured
creatinine clearance from 24-hour urine collections or estimated by the Cockcroft and Gault
formula.34,35
. The equation is:
GFR = 186 x (SCr)-1.154 x (age)-0.203 x (0.742 if female) x (1.210 if African American)
The equation was re-expressed in 2005 for use with a standardized serum creatinine assay,
which yields 5 percent lower values for serum creatinine concentration 36,37
GFR = 175 x (Standardized SCr)-1.154 x (age)-0.203 x (0.742 if female) x (1.210 if
African American)
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GFR is expressed in mL/min/1.73 m2, SCr is serum creatinine expressed in mg/dL, and age
is expressed in years. In the MDRD Study, the equation has an R 2 value of 89.2%, with 91%
and 98% of the estimated values falling within 30% and 50% of measured values,
respectively.
The MDRD study equation includes a term for the African American race to account for the
fact that African Americans have a higher GFR than Caucasians (and other races included in
the MDRD Study) at the same level of serum creatinine. This is due to higher average
muscle mass and creatinine generation rate in African Americans. Clinical laboratories may
not collect data on race and therefore may report GFR estimates using the equation for
Caucasians. For African Americans, multiply the GFR estimate for Caucasians by 1.21.
The MDRD study equation includes a term for age to account for the fact that younger
people have a higher GFR than older people at the same level of serum creatinine. This is
due to higher average muscle mass and creatinine generation rate in younger people.
Applicability of the MDRD Study equation
The MDRD Study equation was developed in a group of patients with chronic kidney
disease (mean GFR 40 mL/min/1.73 m2) who were predominantly Caucasian, non-diabetic
and did not have a kidney transplant.36
The MDRD Study equation has now been evaluated
in numerous populations, including African Americans, Europeans, and Asians with non-
diabetic kidney disease, diabetic patients with and without kidney disease, kidney transplant
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recipients and potential kidney donors. These studies have shown that the MDRD Study
equation has reasonable accuracy in non-hospitalized patients thought to have CKD,
regardless of diagnosis.38
10
Populations or individuals where the MDRD Study equation cannot be applied:
The MDRD Study equation has been reported to be less accurate in populations without
kidney disease, such as young patients with type 1 diabetes without microalbuminuria or
people selected for evaluation of kidney donation.38
The MDRD Study equation has not
been validated in children (age 85 years), or
in some racial or ethnic subgroups, such as Hispanics. Furthermore, any of the limitations
with the use of serum creatinine related to nutritional status or medication usage are not
accounted for in the MDRD Study equation .
Cockcroft and Gault and MDRD Study equations differ:
The Cockcroft and Gault equation estimates creatinine clearance and is not adjusted for
body surface area.33
The MDRD Study equation estimates GFR adjusted for body surface
area. GFR estimates from the MDRD Study equation can therefore be applied to determine
level of kidney function, regardless of a patient’s size. In contrast, estimates based on the
Cockcroft and Gault equation can be used for drug dosage recommendations, whereas GFR
estimates based on the MDRD Study should be "unadjusted" for body surface area. Many
studies have compared the performance of the two equations to measured GFR. In some of
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these studies, the MDRD Study equation was more accurate than the Cockcroft and Gault
equation. Other studies demonstrated similar performance. The Cockcroft and Gault
equation appears to be less accurate than the MDRD Study equation, specifically in older
and obese people.39
In general, drug dosing is based on pharmacokinetic studies where
kidney function was assessed using creatinine clearance levels estimated from the Cockcroft
and Gault equation. For the majority of patients, the difference in GFR estimates based on
the MDRD Study and the Cockcroft and Gault equations will not lead to a difference in drug
dosages. If the estimates differ, the Cockcroft and Gault estimate should be used to be
consistent with pharmacokinetic studies.
Estimating equations are limited by: (1) use of serum creatinine as a filtration marker;
(2) Decreased accuracy at higher levels of estimated GFR; and (3) non-steady state
conditions for the filtration marker when GFR is changing.
Despite these limitations, GFR estimates using equations are more accurate than serum
creatinine alone. Understanding these limitations should help clinicians interpret GFR
estimates. In particular, GFR estimates will be underestimates of true GFR in individuals
with GFR levels >60 mL/min/1.73 m2. As such, GFR estimates may not be useful for
quantification of declines in GFR to levels of 60 mL/min/1.73 m2 or more and may lead to a
“false positive” diagnosis of CKD (GFR under 60 milliliters per minute per 1.73m2) in
people with mildly reduced GFR. However, even in the general population, an estimated
GFR under 60 milliliters per minute per 1.73 m2 is associated with an increased risk of
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adverse outcomes of CKD.40
If more accurate estimation of GFR is necessary, then one
should obtain a clearance measurement.
Creatinine is a 113 dalton amino acid derivative that is generated from the breakdown of
creatine in muscle, distributed throughout total body water, and excreted by the kidneys
primarily by glomerular filtration. Although the serum level is affected primarily by the
level of GFR, it is also affected by other physiological processes, such as tubular secretion,
generation and extra renal excretion of creatinine. Due to variation in these processes
amongst individuals and over time within individuals, particularly the variation in creatinine
generation, the cutoff for normal versus abnormal serum creatinine concentration differs
among groups. In addition, assays for serum creatinine vary across clinical laboratories,
leading to differences in GFR estimates for the same patient when creatinine is measured in
different labs. Because of the wide range of normal for serum creatinine in most clinical
laboratories, GFR must decline to approximately half the normal level before the serum
creatinine concentration rises above the upper limit of normal. The main factors affecting
creatinine generation are muscle mass and diet. Table 1 shows the effect on serum creatinine
of factors affecting creatinine generation.
3.7 Factors that affect creatinine secretion
Some medications, including trimethoprim, cimetidine and some older cephalosporins,
inhibit tubular secretion of creatinine, thereby decreasing creatinine clearance and increasing
serum creatinine without a change in GFR.
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Impact of calibration and inter-laboratory variation of serum creatinine assays on the
estimation of GFR:
The most commonly used assay for serum creatinine, the alkaline picrate (“Jaffe”) assay,
detects a color change when creatinine interacts with picrate under alkaline conditions and is
subject to interference from substances other than creatinine (“non-creatinine chromogens”),
such as proteins and ketoacids. Newer enzymatic methods improve upon some of the non-
specificities of the alkaline picrate assay but some are subject to other interferences.
Calibration of creatinine assays to adjust for this interference is not standardized across
methods and laboratories. Since the concentration of non-creatinine chromogens does not
increase as GFR declines, the difference in serum creatinine assays between laboratories is
greater at low serum creatinine values; therefore, differences in GFR estimates related to
differences in calibration are most apparent at higher levels of GFR.41
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Table 1: Factors affecting serum creatinine concentration.42
Measurement of creatinine clearance should be considered in circumstances when the
estimating equation based on serum creatinine is suspected to be inaccurate (Refer to Table
2) or patients with estimated GFR >60 mL/min/1.73 m2 when a more accurate clearance
measure is required for clinical decision making. Such circumstance may occur in people
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who are undergoing evaluation for kidney donation, treatment with drugs with significant
toxicity that are excreted by the kidneys (for example, high-dose methotrexate) or
consideration for participation in research protocols
Table 2: Indications for a clearance measurement because estimates based on serum
creatinine may be inaccurate
/comment
Routinely, the creatinine clearance is performed by obtaining a 4-,12-,or 24- hour urine
specimen and also a blood specimen sometime within the period of urine collection. The
volume of the urine is measured, urine flow rate is measured, urine flow rate is calculated
(in milliliters per minute ), and the assay for creatinine is performed on plasma and urine to
obtain the concentration in milligrams per deciliter ( or millimoles per liter ). This method
has been adopted since there are limitations to Above mentioned equations based on serum
creatinine.
It can be seen that the plasma concentration of creatinine is inversely proportional to
clearance of creatinine. Therefore, When plasma creatinine concentration is elevated, GFR
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is decreased, indicating renal damage. Unfortunately, plasma creatinine is a relatively
insensitive marker and may not be measurably increased until renal function has deteriorated
more than 50%.43
The observed relationship between plasma creatinine and GFR and the
observation that plasma creatinine concentrations are relatively constant and unaffected by
diet should make creatinine a good analyte for the assessment of renal function. However,
because of the difficulties encountered in analyzing the small amont of creatinine normally
present , measurement of plasma creatinine may not provide sensitivity for the detection of
mild renal dysfunction. Several other analytes, including cystatin C, have been proposed to
monitor.
The serum creatinine level is often used in clinical practice as
an index of kidney function,
but abnormal values may not be present until the glomerular filtration rate (GFR) has
decreased by 50-80%
44 . Because of the limitations associated with the
serum creatinine, the
24-hour creatinine clearance is still the standard clinical technique for measuring GFR, but
even this measurement is far from ideal. A 24-hour urine collection is
an inconvenient
outpatient measurement that restricts mobility; mandates two trips to the hospital or clinic;
and requires urine collection, storage, and transport. Most important for both
outpatients and
inpatients, the creatinine clearance measurement will not be accurate if the urine collection is
incomplete. Even if the urine collection is complete, the clearance measurement
can be
affected by muscle mass and diet. Creatine from ingested meat is converted to creatinine and
can account for as much as 30% of total creatinine excretion45. Creatinine is excreted not
only by glomerular filtration but also by the renal tubule. The secretion of creatinine varies
substantially both in the same individuals over time and among different individuals
46,47. In
addition, the proportion of total renal creatinine excretion due to tubular secretion increases
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with decreasing kidney function 48
. This is particularly problematic in the follow-up of
patients with a significant degree of renal dysfunction because the GFR
can fall more rapidly
than indicated by either serum creatinine or creatinine clearance.
3.8 KIDNEY
The kidneys are organs that have numerous biological roles. Their primary role is to
maintain the homeostatic balance of bodily fluids by filtering and secreting metabolites
(such as urea) and minerals from the blood and excreting them, along with water, as urine.
Because the kidneys are poised to sense plasma concentrations of ions such as sodium,
potassium, hydrogen, and compounds such as amino acids, creatinine, bicarbonate, and
glucose, they are important regulators of blood pressure, glucose metabolism, and
erythropoiesis (the process by which red blood cells (erythrocytes) are produced). The
medical field that studies the kidneys and diseases of the kidney is called nephrology.49
3.8.1 ANATOMY
In humans, the kidneys are located in the posterior part of the abdominal cavity. There are
two, one on each side of the spine; the right kidney sits just below the diaphragm and
posterior to the liver, the left below the diaphragm and posterior to the spleen. Above each
kidney is an adrenal gland (also called the suprarenal gland). The asymmetry within the
abdominal cavity caused by the liver results in the right kidney being slightly lower than the
left one while the left kidney is located slightly more medial. The bulk of water re-
absorption in the vertebrate kidney takes place in the loop of Henle.
The kidneys are retroperitoneal and range from 9 to 13 cm in diameter; the left slightly
larger than the right. They are approximately at the vertebral level T12 to L3. The upper
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parts of the kidneys are partially protected by the eleventh and twelfth ribs, and each whole
kidney and adrenal gland are surrounded by two layers of fat (the perirenal and pararenal
fat) and the renal fascia which help to cushion it. Congenital absence of one or both kidneys,
known as unilateral (on one side) or bilateral (on both the sides) renal agenesis, can occur.
Renal agenesis is also the base for the renal anal gland which helps the large intestine absorb
water.
The kidneys receive unfiltered blood directly from the heart through the abdominal aorta
which then branches to the left and right renal arteries. Filtered blood then returns by the left
and right renal veins to the inferior vena cava and then the heart. Renal blood flow accounts
for 20-25% of the cardiac output.50
figure: 1
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figure: 2
figure: 3
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3.8.2 PHYSIOLOGY OF KIDNEY:
The renal corpuscle is the site of the nephron, where blood is "filtered".
The blood enters the kidney through the renal artery in the renal sinus. It branches into
segmental arteries, which further divide into interlobar arteries penetrating the renal capsule
and extending through the renal columns between the renal pyramids. The interlobar arteries
then supply blood to the arcuate arteries that run through the boundary of the cortex and the
medulla. Each arcuate artery supplies a variety of additional interlobar arteries that feed into
the afferent arterioles to be filtered through the nephrons. After filtration occurs the blood
moves through a small network of venules that converge into interlobar veins. As with the
arteriole distribution the veins follow the same pattern, the interlobar provide blood to the
arcuate veins then back to the interlobar veins which come to form the renal vein exiting the
kidney for transfusion for blood.
Blood filtering takes place in the nephron, which is found in the kidney.
3.8.3 FUNCTION
Excretion of waste products
The kidneys excrete a variety of waste products produced by metabolism, including the
nitrogenous wastes: urea (from protein catabolism) and uric acid (from nucleic acid
metabolism) and water.
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Homeostasis
The kidney is one of the major organs involved in whole-body homeostasis. Among its
homeostatic functions are acid-base balance, regulation of electrolyte concentrations, control
of blood volume, and regulation of blood pressure. The kidneys accomplish these
homeostatic functions independently and through coordination with other organs,
particularly those of the endocrine system. The kidney communicates with these organs
through hormones secreted into the bloodstream.
Acid-base balance
The kidneys regulate the pH of blood by adjusting H+ ion levels, referred as augmentation of
mineral ion concentration, as well as water composition of the blood. Renal production of
bicarbonate (HCO3 –
) ions buffer pH by reducing hydrogen ion concentrations in plasma; the
bicarbonate serves as a proton acceptor.
Blood pressure
Sodium ions are controlled in a homeostatic process involving aldosterone which increases
sodium ion reabsorption in the distal convoluted tubules.
Plasma volume
Any significant rise or drop in plasma osmolality is detected by the hypothalamus, which
communicates directly with the posterior pituitary gland. A rise in osmolality causes the
gland to secrete antidiuretic hormone (ADH), resulting in water reabsorption by the kidney
and an increase in urine concentration. The two factors work together to return the plasma
osmolality to its normal levels.
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ADH binds to principal cells in the collecting duct that translocate aquaporins to the
membrane allowing water to leave the normally impermeable membrane and be reabsorbed
into the body by the vasa recta, thus increasing the plasma volume of the body.
There are two systems that create a hyperosmotic medulla and thus increase the body plasma
volume: Urea recycling and the 'single effect.'
Urea is usually excreted as a waste product from the kidneys. However, when plasma blood
volume is low and ADH is released the aquaporins that are opened are also permeable to
urea. This allows urea to leave the collecting duct into the medulla creating a hyperosmotic
solution that 'attracts' water. Urea can then re-enter the nephron and be excreted or recycled
again depending on whether ADH is still present or not.
The 'Single effect' describes the fact that the ascending thick limb of the loop of Henle is not
permeable to water but is permeable to NaCl. This means that a countercurrent system is
created whereby the medulla becomes increasingly concentrated setting up a osmotic
gradient for water to follow should the aquaporins of the collecting duct be opened by ADH.
Hormone secretion
The kidneys secrete a variety of hormones. Erythropoietin is released in response to low
levels of O2 in the renal circulation. It stimulates erythrocyte production in red bone marrow.
Calcitriol, the activated form of vitamin D, promotes the absorption of Ca2+
from the gut and
the excretion of PO32-. They both help to increase Ca2+
levels.The kidneys also secrete
Renin, an enzyme involved in the regulation of aldosterone secretion by the renin-
angiotensin-aldosterone system.
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Renal failure can broadly be divided into two categories: acute or chronic renal failure. The
type of renal failure is determined by the trend in the serum creatinine.
3.8.4 Acute renal failure
Acute renal failure (ARF), also known as acute kidney failure or acute kidney injury, is a
rapid loss of renal function due to damage to the kidneys, resulting in retention of
nitrogenous (urea and creatinine) and non-nitrogenous waste products that are normally
excreted by the kidney. Depending on the severity and duration of the renal dysfunction, this
accumulation is accompanied by metabolic disturbances, such as metabolic acidosis
(acidification of the blood) and hyperkalaemia (elevated potassium levels), changes in body
fluid balance, and effects on many other organ systems. It can be characterised by oliguria or
anuria (decrease or cessation of urine production), although nonoliguric ARF may occur. It
is a serious disease and treated as a medical emergency.
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Kidney showing marked pallor of the cortex, contrasting to the darker areas of surviving
medullary tissue. The patient died with acute renal failure.
Causes
Acute renal failure is usually categorised (as in the flowchart below) according to pre-renal,
intrinsic and post-renal causes.
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Acute Renal Failure
Pre-renal In trinsic Post-renal
Pre-renal (causes in the blood supply):
hypovolemia (decreased blood volume), usually from shock or dehydration and fluid loss or
excessive diuretics use.
hepatorenal syndrome in which renal perfusion is compromised in liver failure
vascular problems, such as atheroembolic disease and renal vein thrombosis (which can
occur as a complication of the nephrotic syndrome)
infection usually sepsis, systemic inflammation due to infection
severe burns
sequestration due to pericarditis and pancreatitis
hypotension due to antihypertensives and vasodilators
Intrinsic (damage to the kidney itself) [It is most irreversible of the 3]:
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toxins or medication (e.g. some NSAIDs, aminoglycoside antibiotics, iodinated contrast,
lithium, phosphate nephropathy due to bowel preparation for colonoscopy with sodium
phosphates)
rhabdomyolysis (breakdown of muscle tissue) - the resultant release of myoglobin in the
blood affects the kidney; it can be caused by injury (especially crush injury and extensive
blunt trauma), statins, stimulants and some other drugs
hemolysis (breakdown of red blood cells) - the hemoglobin damages the tubules; it may be
caused by various conditions such as sickle-cell disease, and lupus erythematosus
multiple myeloma, either due to hypercalcemia or "cast nephropathy" (multiple myeloma
can also cause chronic renal failure by a different mechanism)
acute glomerulonephritis which may be due to a variety of causes, such as anti glomerular
basement membrane disease/Goodpasture's syndrome, Wegener's granulomatosis or acute
lupus nephritis with systemic lupus erythematosus
Post-renal (obstructive causes in the urinary tract) due to:
medication interfering with normal bladder emptying (e.g. anticholinergics).
benign prostatic hypertrophy or prostate cancer.
kidney stones.
due to abdominal malignancy (e.g. ovarian cancer, colorectal cancer).
obstructed urinary catheter.
drugs that can cause crystalluria and drugs that can lead to myoglobinuria & cystitis
Diagnosis
In general, renal failure is diagnosed when either creatinine or blood urea nitrogen tests are
markedly elevated in an ill patient, especially when oliguria is present. Previous
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measurements of renal function may offer comparison, which is especially important if a
patient is known to have chronic renal failure as well. If the cause is not apparent, a large
amount of blood tests and examination of a urine specimen is typically performed to
elucidate the cause of acute renal failure, medical ultrasonography of the renal tract is
essential to rule out obstruction of the urinary tract.
Consensus criteria (RIFLE)52,53
for the diagnosis of ARF are:
Risk: serum creatinine increased 1.5 times OR urine production of 44) or urine output
below 0.3 ml/kg for 24 h
Loss: persistent ARF or complete loss of kidney function for more than four weeks
End-stage Renal Disease: complete loss of kidney function for more than three months
Kidney biopsy may be performed in the setting of acute renal failure, to provide a definitive
diagnosis and sometimes an idea of the prognosis, unless the cause is clear and appropriate
screening investigations are reassuringly negative.
Treatment
Acute renal failure may be reversible if treated promptly and appropriately. Resuscitation to
normotension and a normal cardiac output is key. The main interventions are monitoring
fluid intake and output as closely as possible; insertion of a urinary catheter is useful for
monitoring urine output as well as relieving possible bladder outlet obstruction, such as with
an enlarged prostate. In the absence of fluid overload, administering intravenous fluids is
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typically the first step to improve renal function. Fluid administration may be monitored
with the use of a central venous catheter to avoid over- or under-replacement of fluid. If the
cause is obstruction of the urinary tract, relief of the obstruction (with a nephrostomy or
urinary catheter) may be necessary. Metabolic acidosis and hyperkalemia, the two most
serious biochemical manifestations of acute renal failure, may require medical treatment
with sodium bicarbonate administration and antihyperkalemic measures, unless dialysis is
required.
Should hypotension prove a persistent problem in the fluid replete patient, inotropes such as
norepinephrine and/or dobutamine may be given to improve cardiac output and hence renal
perfusion. While a useful pressor, there is no evidence to suggest that dopamine is of any
specific benefit,54
and at least a suggestion of possible harm. A Swan-Ganz catheter may be
used, to measure pulmonary artery occlusion pressure to provide a guide to left atrial
pressure (and thus left heart function) as a target for inotropic support.
The use of diuretics such as furosemide, while widespread and sometimes convenient in
ameliorating fluid overload, does not reduce the risk of complications and death.55 In
practice, diuretics may simply mask things, making it more difficult to judge the adequacy
of resuscitation.
The use of an ACE Inhibitor (such as benazepril) can help protect renal function in patients
with advanced renal insufficiency.56
However, an increase of up to 30% in SCr (serum
creatinine) is expected. This is because the ACEI reduces Angiotensin II levels. Angiotensin
II causes renal efferent arteriole vasoconstriction, and reduction of angiotensin II leads to
vasodialation which in turn reduces GFR. This reduction in GFR causes the predicted
increase in SCr.
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However, one must not use a NSAID as NSAIDs reduce prostaglandin production.
Prostaglandins cause vasodialation of the renal afferent arteriole, and a reduction in
prostaglandin leads to vasoconstriction thus reducing GFR. However, this can lead to
nephrotoxicity and thus NSAIDs must be avoided.57
Lack of improvement with fluid resuscitation, therapy-resistant hyperkalemia, metabolic
acidosis, or fluid overload may necessitate artificial support in the form of dialysis or
hemofiltration. Depending on the cause, a proportion of patients will never regain full renal
function, thus having end stage renal failure requiring lifelong dialysis or a kidney
transplant.
History
Before the advancement of modern medicine, acute renal failure might be referred to as
uremic poisoning. Uremia was the term used to describe the contamination of the blood with
urine. Starting around 1847 this term was used to describe reduced urine output, now known
as oliguria, which was thought to be caused by the urine's mixing with the blood instead of
being voided through the urethra.
Acute renal failure due to acute tubular necrosis (ATN) was recognised in the 1940s in the
United Kingdom, where crush victims during the Battle of Britain developed patchy necrosis
of renal tubules, leading to a sudden decrease in renal function.58
During the Korean and
Vietnam wars, the incidence of ARF decreased due to better acute management and
intravenous infusion of fluids.59
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3.8.5 Chronic kidney disease
Chronic kidney disease (CKD), also known as chronic renal disease, is a progressive loss of
renal function over a period of months or years. The symptoms of worsening kidney
function are unspecific, and might include feeling generally unwell and experiencing a
reduced appetite. Often, chronic kidney disease is diagnosed as a result of screening of
people known to be at risk of kidney problems, such as those with high blood pressure or
diabetes and those with a blood relative with chronic kidney disease. Chronic kidney disease
may also be identified when it leads to one of its recognized complications, such as
cardiovascular disease, anemia or pericarditis.52
Chronic kidney disease is identified by a blood test for creatinine. Higher levels of creatinine
indicate a falling glomerular filtration rate (rate at which the kidneys filter blood) and as a
result a decreased capability of the kidneys to excrete waste products. Creatinine levels may
be normal in the early stages of CKD, and the condition is discovered if urinalysis (testing of
a urine sample) shows that the kidney is allowing the loss of protein or red blood cells into
the urine. To fully investigate the underlying cause of kidney damage, various forms of
medical imaging, blood tests and often renal biopsy (removing a small sample of kidney
tissue) are employed to find out if there is a reversible cause for the kidney malfunction.
Recent professional guidelines classify the severity of chronic kidney disease in five stages,
with stage 1 being the mildest and usually causing few symptoms and stage 5 being a severe
illness with poor life expectancy if untreated. Stage 5 CKD is also called established
chronic kidney disease and is synonymous with the now outdated terms end-stage renal
disease (ESRD), chronic kidney failure (CKF) or chronic renal failure (CRF).60
There is no
specific treatment unequivocally shown to slow the worsening of chronic kidney disease. If
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there is an underlying cause to CKD, such as vasculitis, this may be treated directly with
treatments aimed to slow the damage. In more advanced stages, treatments may be required
for anemia and bone disease. Severe CKD requires one of the forms of renal replacement
therapy; this may be a form of dialysis, but ideally constitutes a kidney transplant.60
Signs and symptoms:
Initially it is without specific symptoms and can only be detected as an increase in serum
creatinine or protein in the urine. As the kidney function decreases:
blood pressure is increased due to fluid overload and production of vasoactive hormones,
increasing one's risk of developing hypertension and/or suffering from congestive heart
failure
Urea accumulates, leading to azotemia and ultimately uremia (symptoms ranging from
lethargy to pericarditis and encephalopathy). Urea is excreted by sweating and crystallizes
on skin ("uremic frost").
Potassium accumulates in the blood (known as hyperkalemia with a range of symptoms
including malaise and potentially fatal cardiac arrhythmias)
Erythropoietin synthesis is decreased (potentially leading to anemia, which causes fatigue)
Fluid volume overload - symptoms may range from mild edema to life-threatening
pulmonary edema
Hyperphosphatemia - due to reduced phosphate excretion, associated with hypocalcemia
(due to vitamin D3 deficiency). The major sign of hypocalcemia being tetany.
Later this progresses to tertiary hyperparathyroidism, with hypercalcaemia, renal
osteodystrophy and vascular calcification that further impairs cardiac function.
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Metabolic acidosis, due to accumulation of sulfates, phosphates, uric acid etc. This may
cause altered enzyme activity by excess acid acting on enzymes and also increased
excitability of cardiac and neuronal membranes by the promotion of hyperkalemia due to
excess acid (acidemia)61
People with chronic kidney disease suffer from accelerated atherosclerosis and are more
likely to develop cardiovascular disease than the general population. Patients afflicted with
chronic kidney disease and cardiovascular disease tend to have significantly worse
prognoses than those suffering only from the latter.
Diagnosis
In many CKD patients, previous renal disease or other underlying diseases are already
known. A small number presents with CKD of unknown cause. In these patients, a cause is
occasionally identified retrospectively.
It is important to differentiate CKD from acute renal failure (ARF) because ARF can be
reversible. Abdominal ultrasound is commonly performed, in which the size of the kidneys
are measured. Kidneys with CKD are usually smaller (< 9 cm) than normal kidneys with
notable exceptions such as in diabetic nephropathy and polycystic kidney disease. Another
diagnostic clue that helps differentiate CKD and ARF is a gradual rise in serum creatinine
(over several months or years) as opposed to a sudden increase in the serum creatinine
(several days to weeks). If these levels are unavailable (because the patient has been well
and has had no blood tests) it is occasionally necessary to treat a patient briefly as having
ARF until it has been established that the renal impairment is irreversible.
Additional tests may include nuclear medicine MAG3 scan to confirm blood flows and
establish the differential function between the two kidneys. DMSA scans are also used in
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Stage 1 CKD
Slightly diminished function; Kidney damage with normal or relatively high GFR (>90
mL/min/1.73 m2). Kidney damage is defined as pathologic abnormalities or markers of
damage, including abnormalities in blood or urine test or imaging studies.60
Stage 2 CKD
Mild reduction in GFR (60-89 mL/min/1.73 m2) with kidney damage. Kidney damage is
defined as pathologic abnormalities or markers of damage, including abnormalities in blood
or urine test or imaging studies.60
Stage 3 CKD
Moderate reduction in GFR (30-59 mL/min/1.73 m2).
60 British guidelines distinguish
between stage 3A (GFR 45-59) and stage 3B (GFR 30-44) for purposes of screening and
referral.60
Stage 4 CKD
Severe reduction in GFR (15-29 mL/min/1.73 m2) Preparation for renal replacement therapy
Stage 5 CKD
Established kidney failure (GFR
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Causes
The most common causes of CKD are diabetic nephropathy, hypertension, and
glomerulonephritis. Together, these cause approximately 75% of all adult cases. Certain
geographic areas have a high incidence of HIV nephropathy.62
Vascular, includes large vessel disease such as bilateral renal artery stenosis and small
vessel disease such as ischemic nephropathy, hemolytic-uremic syndrome and vasculitis
Glomerular, comprising a diverse group and subclassified into
Primary Glomerular disease such as focal segmental glomerulosclerosis and IgA nephritis
Secondary Glomerular disease such as diabetic nephropathy and lupus nephritis
Tubulointerstitial including polycystic kidney disease, drug and toxin-induced chronic
tubulointerstitial nephritis and reflux nephropathy
Obstructive such as with bilateral kidney stones and diseases of the prostate
Treatment:
The goal of therapy is to slow down or halt the otherwise relentless progression of CKD to
stage 5. Control of blood pressure and treatment of the original disease, whenever feasible,
are the broad principles of management. Generally, angiotensin converting enzyme
inhibitors (ACEIs) or angiotensin II receptor antagonists (ARBs) are used, as they have been
found to slow the progression of CKD to stage 5.63,64
Replacement of erythropoietin and vitamin D3, two hormones processed by the kidney, is
usually necessary, as is calcium. Phosphate binders are used to control the serum phosphate
levels, which are usually elevated in chronic kidney disease.
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When one reaches stage 5 CKD, renal replacement therapy is required, in the form of either
dialysis or a transplant.
In some cases, dietary modifications have been proven to slow and even reverse further
progression. Generally this includes limiting a person’s intake of protein.
Prognosis
The prognosis of patients with chronic kidney disease is guarded as epidemiological data has
shown that all cause mortality (the overall death rate) increases as kidney function
decreases.65
The leading cause of death in patients with chronic kidney disease is
cardiovascular disease, regardless of whether there is progression to stage 5.66,67,68
While renal replacement therapies can maintain patients indefinitely and prolong life, the
quality of life is severely affected.67,68
Renal transplantation increases the survival of
patients with stage 5 CKD significantly when compared to other therapeutic
options;69,70however, it is associated with an increased short-term mortality (due to
complications of the surgery). Transplantation aside, high intensity home hemodialysis
appears to be associated with improved survival and a greater quality of life, when compared
to the conventional three times a week hemodialysis and peritoneal dialysis.71
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4. MATERIAL AND METHOD
4.1 Source Of Data
50 Healthy volunteers are selected based on criteria. Out of these, 25 volunteers will be
female and 25 volunteers will be male. The study will be carried out in Department of
Clinical Biochemistry, St. John Medical College Hospital, Bangalore.
4.2 Criteria
Inclusion Criteria: Healthy Volunteer of 20-30 year age group
Exclusion Criteria: Renal dysfunction
Conditions with increased Serum and urine creatinine
4.3 Method of Sample Collection:
Each volunteer will be given 2 cans for urine collection. Urine collection will begin at 7 am
in the morning on day 1 till 7 am on day 2 (next day); The first can is used for collection
from 7 am to 7 pm on day 1. The second can will be used for another 12 hour collection
study from 7pm on day 1 to 7am on day 2. Mix well and measure the volume separately in
both the can. Take 5ml of sample from the first can; labeled it as sample1. Then mix both
the contents of the can by transferring from can 1 to can 2 .Mix well and take another 5ml of
sample; labeled it as sample 2. Sample1will pertain to 12-hour turned urine collection.
Sample 2 will pertain to 24-hour turned urine collection.
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4.4 Method of Creatinine Analysis:
The creatinine is measured by using modification of the kinetic Jaffe reaction72
. This
method has been reported to be less susceptible than conventional method to interference
from non creatinine, Jaffe positive compound. Creatinine is generally regarded as the most
useful endogenous substance to measure for the assessment of kidney function73
.
4.5 Principle:
In the presence of a strong base such as NaOH, lithium picrate reacts with creatinine to form
a red chromophore. The rate of increasing absorbance at 510 nm due to the formation of this
chromophore is directly proportional to the creatinine concentration in the sample and is
measured using a bichromatic (510, 600 nm) rate technique. Bilirubin is oxidized by
potassium ferricyanide74
to prevent interference.
The Cockcroft–Gault formula is used for calculation of creatinine clearance. It is corrected
for body surface area which may have significance with short or tall frames. The results
were accepted based on the acceptable Quality control run.
Formula for Creatinine Clearance = UxV x 1.73
P A
U= Urinary Creatinine concentration in mg/dL
V= Volume of urine per minute or total volume / 24h x 60 min
P = Plasma or Serum Creatinine Concentration in mg/dL
A = Body surface Area derived from the patients’s height and weight.
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5. STASTICAL ANALYSIS:
The samples were analyzed statistically by using paired sample ‘t’ test. The pearson’s
correlation was doen to evaluate if there was correlation between the samples.
6. RESULT:
Table 3 depicts the descriptive statistics for Creatinine Clearance for all the samples (both
males and females) and also gender wise. Table 4 depicts the mean difference, standard
deviation and standard error with 95% Confidence Interval. The person’s correlation
between 12-h and 24-h urine samples showed a significant correlation in both males and
females (r = 0.8 and 0.6 respectively, p values < 0.05)
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7. TABLE
Table 3 : Descriptive statistic of Creatinine Clearance
12 – h Creatinine Clearance 24-h Creatinine Clearance
95 % C.I 95 % C.IMean S.D S.E
Lower
bound
Upper
bound
Mean S.D S.E
Lower
bound
Upper
bound
Cr Cl
for all
samples
88.5 9.0 1.3 89.3 97.3 101 11.4 1.6 103.6 112.3
Cr Cl in
males
93 9.7 1.9 89.3 97.3 108 10.5 2.1 103.6 112.3
Cr Cl in
Females
83.7 4.8 1.0 81.8 85.8 95.3 8.4 1.6 91.9 98.9
*SD signifies standard deviation
*SE signifies standard error.
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Table 4 : Comparison of groups for Creatinine Clearnce for 12-h and 24-h urine
collection
95 % C. IMean
difference
SD SE
Lower
bound
Upper
bound
‘p’ value
CrCL 12 hr
and
CrCl 24 hr
.
-13.09 7.84 1.109 -15.3 -10.9 < 0.001
CrCL 12 hr
and
CrCl 24 hr
Male.
-14.61 8.42 1.68 -18.1 -11.1 < 0.001
CrCL 12 hr
and
CrCl 24 hr
Female .
-11.56 7.05 1.41 -14.5 -8.6 < 0.001
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8. DISCUSION:
The study was conducted to evaluate the Creatinine Clearance in two different timed urine
collection namely 12-h and 24-h. The study was done to find out if the duration of urine
collection can be reduced from 24-h to 12 h. The results showed there was significant
difference in creatinine clearance in both males and females. The creatinine clearnce was
found to be lower in 12-h urine collection in comparison to 24-h urine collection. The 12 hr
period was during the day i.e., 7am to 7pm on the day 1. The probability the creatinine
clearance is lower during the day than during the night. The diurnal variation is not
incorporated if the urine collection period were to be reduced from 24-h to 12-h. This is
appropriately depicted in our study. There is a significant correlation between 12-h and 24-h
urine collection. There is a difference of approximately 15 % in creatinine clearance
between 12-h and 24-h urine samples.
If circumstance of specimen collection are not defined and controlled, variability in values
for an individual 12 hour and 24 hour clearance can be expected . Rates of glomerular
filtration and creatinine excreation
75normally show diurnal variations which in many people
are large.75,76
.Dietry protein,salt and water balance,physical activity, and even the emotional
state can influence glomerular filteration rate.75
Concentrations of serum creatinine also vary
during a day.77.
The results of the study is very similar to previous studies. Baumann TJ et al in their study
on 10 critically ill patients for accurate determination of creatinine clearance has shown that
an 8-h urine collection is acceptable if the deviation is 20% from the 24-h value. In their
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study, they have shown that the mean difference between each 2-h interval and 24-h interval
were not significantly different. Clearance values determined from 8- and 12-h collections
were within 20 % of the 24-h urine creatinine clearance.78
Another study by Roberti Riera E et al studied 30 children for creatinine clearance in 3- and
24-h urine collection. The study showed no significant difference in these two different
timed urine collections. In their study they have recommended that 3-h urine collection can
be adopted if the patients are adequately hydrated and hospitalized patients especially
infants or young children.
79
Richardson James in his study has showed that there is no significant difference in one-hour
creatinine clearance and 24-hour creatinine clearance.80
9. C0NCLUSION:
In this study the creatinine clearance is significantly different in urine sample collected over
12 hr period and 24 hr period in both male and female but the difference is about 15 %
between the two timed collection. This is clinical acceptable and hence 12 hr urine
collection can be adopted in patients who are well hydrated and it can replace 24-h urine
collection.
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