N A E E M B H O J A N IU R O L O G I S T

U N I V E R S I T Y O F M O N T R E A L

CLINICAL ASPECTS OF RENAL OBSTRUCTION

RENAL OBSTRUCTION

• Plan

• Introduction and definition

• Etiology

• Physiology

• Pathology

• Workup

• Treatment

• Specific situations

INTRODUCTION

• Renal obstruction • Age

• Fetal development

• Childhood

• Adulthood

• Urinary tract• Proximal to the calyces to

• As distal as the urethral meatus

• Cause• Congenital or acquired

• Benign or malignant

• Intrinsic or extrinsic• Intraluminal vs intramural

• Partial or complete

• Unilateral or bilateral

• Acute or chronic

DEFINITIONS

• Hydronephrosis

• Renal pelvis AND calyceal dilatation

• May be associated with obstruction but not necessarily

• Obstructive uropathy

• Functional or anatomic obstruction of urinary flow at any

level of the urinary system

• Obstructive nephropathy

• Obstruction that causes functional or anatomic renal

damage

PREVALENCE

• Autopsy series

• 3.8%1 (3.9% in males, 3.6% in females)

• 20-60 yr olds

• More prevalent in women

• >60

• More prevalent in men

1. Bell ET. Renal Disease. Philadelphia, Lea & Febiger, 1946

ETIOLOGY

RENAL PHYSIOLOGY

• GFR = Kf (PGC – PT – πGC)• Kf : glomerular ultrafiltration coefficient

• PGC : glomerular capillary pressure

• PT : hydraulic pressure of fluid in the tubule

• π: oncotic pressure

• RPF = (aortic pressure – renal venous pressure)renal vascular resistance

• Constriction of the afferent or efferent arterioles or both would reduce RPF (increasing renal vascular resistance).

• Constriction of the afferent arteriole results in a decrease of PGC and GFR

• Increase in efferent arteriolar resistance increases PGC

UNILATERAL URETERAL OBSTRUCTION

Moody TE et al. Invest Urol 1975;13:246-251

UNILATERAL URETERAL OBSTRUCTION

• TRIPHASIC response in RBF and ureteral pressure

• Phase I (1-2 hrs)• Increased RBF

• Increased ureteral pressure

• Vasodilatation of afferent arteriole

• Caused by NO, PGE2

• Stable GFR

• Phase II (2-5 hrs)• Decreased RBF

• Increasing ureteral pressure

• Decreasing GFR

• Short lived efferent vasoconstriction (AT2, TXA2 and endothelin)

• Phase III (>5 hrs)• Decreasing GFR

• Secondary to afferent vasoconstriction and decreasing filtration

BILATERAL URETERAL OBSTRUCTION

• BIPHASIC response in RBF and ureteral pressure

• Phase I (<1 hr)• Mildly increased RBF

• Increased+++ ureteral pressure

• Decreasing GFR

• Only mild early vasodilation (NO, PAF)

• Phase II (1-5 hrs)• Decreasing RBF

• Increased ureteral pressure

• Decreasing GFR

• Prolonged efferent vasoconstriction (AT2, TXA2)

• Phase III (> 5hrs)• Decreasing +++ RBF

• Increased ureteral pressure

• Decreasing GFR

• Secondary to afferent vasoconstriction

PARTIAL OBSTRUCTION

• Dog studies

• No irreversible damage up to 2 weeks

• Minimal recovery of renal function after 8 weeks

• Full recovery at 14 days of partially obstructed kidney

• 31% recovery at 28 days of partially obstructed kidney

• 8% recovery at 60 days of partially obstructed kidney

Ryan PC et al. J Urol. 1987 Sep;138(3):674-8

EFFECTS OF OBSTRUCTION ON TUBULAR FUNCTION

• Decreased urine concentrating ability

• Increased FENa

• Profound in BUO

• Mild in UUO

• If obstruction is acute FENa is actually decreased significantly

PATHOLOGICAL CHANGES WITH OBSTRUCTION AFTER 6 WEEKS

• Gross

• Pelvicaliectasis

• Edematous parenchyma

• Cystic appearance

• Microscopic

• Lymphatic dilatation

• Interstitial edema

• Tubular atrophy

• Interstitial fibrosis

• Macrophage infiltration

• Hemorrhage and necrosis

WORKUP

• Indications for urgent relieve of obstruction

• Unilateral obstruction

• Intractable pain

• N/V

• Signs of sepsis/To

• Bilateral obstruction

• Same as above plus

• Elevated BUN/creat or K+

• Signs and symptoms of uremia

• Signs and symptoms of fluid overload

WORKUP

• Imaging

• U/S• No radiation

• No contrast

• Doppler U/S can calculate resistive indices

• Anatomic not functional

• Operator dependent

• CT scan• Gold standard

• Most accurate

• No contrast

• Low radiation if suspect stones

• More anatomic detail than U/S

• Anatomic not functional unless contrast is used

• Can have allergic or anaphylactic reaction

WORKUP

• Nuclear renal scans

• Functional evaluation

• No contrast

• Negligible radiation

• Essentially no risk of an allergic or anaphylactic reaction

• DTPA (glomerular agent Tc 99m)

• MAG-3 (tubular agent Tc 99m)

TREATMENT

• DECOMPRESSION

• Double j stent vs Nephrostomy tube

TREATMENT

• No consensus

• Dj stent• Advantages

• Very effective

• No incision

• Facilitates ureteroscopy

• Disadvantages

• Stent symptoms

• Stone manipulation usually required

• Stent migration

• Forgotten stent/encrustation

• NPC• Advantages

• Very effective

• No stent symptoms

• Facilitates PNCL

• Disadvantages

• Difficult if no hydro

• External device

• Incision

• Accidental removal

TREATMENT

• No consensus

• Dj stent

• Very effective

• No incision

• Facilitates ureteroscopy

• Stent symptoms

• Stone manipulation usually

required

• Stent migration

• Forgotten stent

• NPC

• Very effective

• No stent symptoms

• Facilitates PNCL

• Difficult if no hydro

• External device

• Incision

• Accidental removal

TREATMENT

• No consensus

• Dj stent

• Very effective

• No incision

• Facilitates ureteroscopy

• Stent symptoms

• Stone manipulation usually

required

• Stent migration

• Forgotten stent

• NPC

• Very effective

• No stent symptoms

• Facilitates PNCL

• Difficult if no hydro

• External device

• Incision

• Accidental removal

DOUBLE J INSERTION

PERCUTANEOUS NEPHROSTOMY PLACEMENT

URETEROPELVIC JUNCTION OBTRUCTION

SPECIFIC SITUATIONS

SPECIFIC SITUATIONS

• UPJ Obstruction

• Etiologies

• Congenital

• Intrinsic

• Aperistaltic segment of ureter

• Congenital stricture

• Extrinsic

• Crossing vessels

• Adhesions

• Acquired

• Stone disease

• Urothelial malignancy

• Iatrogenic scarring/ischemia

• Inflammatory stricture

• Benign upper ureteral fibroepithelial

polyps

SPECIFIC SITUATIONS

• UPJ Obstruction

• Presentation

• Hydronephrosis on perinatal imaging

• Flank mass in neonate

• Intermittent abdominal or flank pain

• Recurrent UTIs/pyelonephritis

• HTN

• Dx

• U/S

• Often first line test

• Triphasic CT scan

• Excellent anatomy

• Can identify crossing vessel

SPECIFIC SITUATIONS

• UPJ Obstruction

• Diagnosis

• DTPA/MAG-3

• Gives quantitative data on differential renal function and

obstruction

• T1/2 <10 mins = normal

• T1/2 >20 mins = obstruction

• T1/2 10-20 mins = indeterminate

• Lasix

• To produce high-flow and r/o dilated but unobstructed system

SPECIFIC SITUATIONS

• UPJ Obstruction

• Indications for treatment

• Bilateral disease

• Renal function impairment (less than 40% with poor washout OR

decreasing function on serial studies

• UTI’s

• Solitary kidney

• Pain

• Kidney stones

• HTN (possible indication)

SPECIFIC SITUATIONS

• UPJ Obstruction

• Management options

• Careful observation with routine reassessment

• LSC or robotic pyeloplasty

• Endopyelotomy

• Nephrectomy (differential function < 12-15%)

SPECIFIC SITUATIONS

• 40 year old female

• Presenting with right flank pain on and off

• No previous medical problems and normal creatinine

• Ultrasound/scan demonstrate mild/moderate

hydronephrosis of the right kidney

• DTPA lasix (F-15) study performed (11/2013)

SPECIFIC SITUATIONS

• 40 year old female

• Presenting with right flank pain on and off

• DTPA lasix study (F-15) performed (05/2014)

SPECIFIC SITUATIONS

• 40 year old female

• Presenting with right flank pain on and off

• DTPA lasix study (F-15) performed (05/2014)

• Hepatobillary consult for gall stones

SPECIFIC SITUATIONS

• 40 year old female

• Presenting with right flank pain ON

• Mag-3 Lasix study (F-15) performed (01/2015)

NEPHROLITHIASIS

SPECIFIC SITUATIONS

SPECIFIC SITUATION

• Nephrolithiasis

• Frequent cause of renal obstruction

• Prevalence of symptomatic stone events

• 11% of men

• 5.6% of women

• Recurrence rates

• 40% at 5 years

• 75% at 20 years

• Stone formation

• Increased rates of chronic kidney disease and HTA

SPECIFIC SITUATION

• Nephrolithiasis

• Presentation• Flank pain

• +/- N/V

• +/- To

• +/- renal insufficiency

• Diagnosis• Scan without contrast

• Mild to severe hydronephrosis

• If staghorn with cortical thinning

• Indication for nuclear medicine to determine function

• If hydro is mild, stone can be difficult to detect and differentiate from phlebolith

• Indication for nuclear medicine

SPECIFIC SITUATION

• Nephrolithiasis

• Presentation• Flank pain

• +/- N/V

• +/- To

• +/- renal insufficiency

• Diagnosis• Scan without contrast

• Mild to severe hydronephrosis

• If staghorn with cortical thinning

• Indication for nuclear medicine to determine function

• If hydro is mild, stone can be difficult to detect and differentiate from phlebolith

• Indication for nuclear medicine

SPECIFIC SITUATION

SPECIFIC SITUATION

SUMMARY

• Renal obstruction is a very common urologic

problem

• Nuclear medicine is essential in determining if

obstruction is present

• Nuclear medicine is essential in determining

differential renal function

• Treatment needs to be effective, appropriate and

prompt

RENAL OBSTRUCTION

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