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CHAPTER 26
ACUTE RENAL FAILURE AND CHRONIC KIDNEY DISEASE
CHAPTER 26
ACUTE RENAL FAILURE AND CHRONIC KIDNEY DISEASE
WHEN KIDNEYS FAIL
Less waste is removed More waste remains in the blood Nitrogenous compounds build up in the blood
BUN: Blood urea nitrogen Creatinine
Renal function approximated by: initial creatinine level/current creatinine level
ACUTE RENAL FAILURE Prerenal
Decreased blood supply Shock, dehydration, vasoconstriction
Postrenal Urine flow is blocked
Stones, tumors, enlarged prostate Intrinsic
Kidney tubule function is decreased Ischemia, toxins, intratubular
obstruction
QUESTION
Which type of acute renal failure (ARF) would be most likely to accompany benign prostatic hypertrophy?
a. Prerenalb. Postrenalc. Intrinsicd. Extrinsic
ANSWER
b. Postrenal Postrenal ARF occurs when the flow of
urine is blocked by kidney stones, tumors, or an enlarged prostate gland. Because the male utethra passes through the prostate, if it is enlarged the urethra may become blocked.
RADIOCONTRAST AGENTS CAN CAUSE ARF
Giving N-acetylcysteine reduces the risk of ARF by 50% in a meta-analysis
Recommended for clients at risk of renal failure who are receiving radiographic contrast media
Diabetics, clients with sepsis Underlying vascular, renal, or hepatic
disease Receiving other nephrotoxic drugs
(Kellum, J.A. [2003]. A drug to prevent renal failure? Lancet 362,589-590.)
SCENARIO
A man developed acute renal failure after emergency surgery for a severed left leg…
He came in with a serum creatinine of 1.2 mg/dL, but now it is 5.6 mg/dL
His BUN is 86 mg/dLQuestion: Why would leg damage cause renal failure? What is his remaining kidney function?
URINE CONTAINING TUBULAR CELL CASTS Casts are formed
when cells are packed together in the tubule lumen
They block the tubule
When the mass of cells washes loose, it appears in the urine
SCENARIO
Mr. J is an alcoholic with kidney problems… He is severely dehydrated with an infected leg
ulcer, benign prostatic hypertrophy, and anemia
His urine is dark and contains myoglobin and tubular cell casts
His creatinine and BUN are both elevated Question: What may have caused his acute tubular
necrosis?
CHRONIC RENAL FAILURE
Fewer nephrons are functioning Remaining nephrons must filter
more Hyperperfusion Hypertrophy
DEVELOPMENT OF CRF
Diminished renal reserve Nephrons are working as hard as they can
Renal insufficiency Nephrons can no longer regulate urine density
Renal failure Nephrons can no longer keep blood
composition normal End-stage renal disease
UREMIA
Uremia = “Urine in the Blood” Renal filtering function decreases
Altered fluid and electrolyte balanceo Acidosis, hyperkalemia, salt wasting,
hypertension Wastes build up in blood
Increased creatinine and BUNo Toxic to CNS, RBCs, platelets
Kidney metabolic functions decrease Decreased erythropoietin Decreased Vitamin D activation
QUESTION
Which of the following renal disorders is characterized by increased BUN and creatinine levels?
a. ARFb. CRFc. Uremiad. All of the abovee. b and c
ANSWER
d. All of the aboveIn each disorder listed, the ability to
remove nitrogenous waste is diminished. This causes nitrogenous compounds (BUN and creatinine) to accumulate in the blood.
SCENARIO
A man has chronic renal failure… He has high creatinine and BUN,
hyperkalemia, acidosis with normal pCO2, and severe anemia
His blood glucose has reached 340 mg/dL one hour after a hospital meal
He complains of having broken two toes in the last few weeks, even though he eats a lot of dairy products for calcium
SCENARIO (CONT.)
Question: What is the most likely cause of
his chronic renal failure? What caused his anemia? Why are his bones brittle even
though he eats dairy products?
CARDIOVASCULAR CONSEQUENCES OF CRF
Decreased blood viscosity
+ Increased blood
pressure +
Decreased oxygen supply
less erythropoietin
anemia
lower blood viscosity
blood flows through vessels more swiftly
heart rate increases
left ventricle dilation and hypertrophy
not enough oxygen to support LV contraction
anginaischemia
LHF
increased workload on left heart
QUESTION
Tell whether the following statement is true or false:
CRF leads to decreased cardiac output (CO).
ANSWER
TrueThe increased blood pressure (HTN) and
hypoxemia that accompany CRF leads to increased myocardial work (the heart has to work harder to meet the metabolic demands of body tissues). Eventually the heart becomes unable to meet these metabolic demands, and CO will decrease.
MANIFESTATIONS OF KIDNEY FAILURE
TYPES OF DIALYSIS