Urinary tract obstruction
Victor Federico B. Acepcion, MD, FPUA
The Kidney Basic function:
formation of ultrafiltrate that is free of protein with appropriate amount of water, electrolytes, and end products of metabolic pathways to maintain homeostasis.
Remaining portion of UT Eliminate and/or store urine
Urine production
Pressure gradient from glomerulus to Bowman capsule
Peristalsis of renalpelvis and ureter
Effects of gravity
Urinary tract obstruction
• Common cause of acute and chronic renal failure
• Potentially curable form of kidney disease
Definition of terms Obstructive uropathy Obstructive nephropathy Hydronephrosis
Objectives Define urinary tract obstruction Incidence Etiology/pathophysiology Clinical presentation Diagnosis Treatment and management
Pre-hospital/emergency department care
Incidence• Frequency
– No data available in unselected populations– 20-35% prevalence in large survey among elderly
men– 3.8% (adults); 2.0% (children) postmortem
examinations• Sex
– No gender difference until 20 years– Women 20-60; Men > 60
• Age– Special considerations in pediatric patients
Etiology Types of obstruction
Mechanical blockade Intrinsic extrinsic
Functional defects Congenital
Common Mechanical Causes of Urinary Tract Obstruction
Ureter Bladder Outlet
Urethra
CONGENITAL
Ureteropelvic junction narrowing or obstruction
Bladder neck obstruction
Posterior urethral valves
Ureterovesical junction narrowing or obstruction and reflux
Ureterocele Anterior urethral valves
Ureterocele Damage to S2-4
Stricture
Retrocaval ureter
Meatal stenosis
VUR VUR Phimosis
Ureter Bladder Outlet
Urethra
Acquired Intrinsic Defects
Calculi Benign prostatic hyperplasia
stricture
Inflammation
Cancer of the prostate
tumor
Infection Cancer of the bladder
calculi
Trauma Calculi trauma
Sloughed Papillae
Diabetic neuropathy
phimosis
Tumor Spinal cord disease
Blood Clots Anticholinergic drugs and alpha adrenergic antagonists
Uric acid crystals
Ureter Bladder Outlet
Urethra
Acquired Extrinsic Defects
Pregnant uterus
Carcinoma of cervix, colon
trauma
Retroperitoneal fibrosis
trauma
Aortic aneurysm
Uterine leiomyomata
Carcinoma of uterus, prostate, bladder, colon, rectum
lymphoma
Pelvic inflammatory disease, endometriosis
Accidental surgical ligation
Pathophysiology Unilateral (UUO)? Bilateral (BUO)? Obstruction relieved or not? Time
Global Renal Function Changes Obstruction can affect hemodynamic variables and GFR GFR= Kf(PGC-PT-GC)
RPF= (aortic pressure-renal venous pressure) renal vascular resistance
Influences PGC Constriction of the afferent arteriole will result in a
decrease of PGC and GFR An increase in efferent arteriolar resistance will increase
PGC
Kf- glomerular ultrafiltration coeffecient related to the surface area and permeability of the capillary membranePGC- glomerular capillary pressure. Influenced by renal plasma flow and the resistance of the afferent and efferent arteriolesPT- Hydraulic pressure of fluid in the tubule- the oncotic pressure of the proteins in the glomerular capillary and efferent arteriolar blood
Triphasic pattern of UUO
Bilateral urinary obstruction (BUO) • No triphasic pattern• Modest increase in RBF after 90 min but
between 90 min to 7 hours, RBF is significantly lower than UUO.
• Increase renal vascular resistance (RVR)• After 24 hours, low RBF, high RVR same as
UUO
Bilateral urinary obstruction (BUO) Ureteral pressure higher than in UUO Effective RBF is markedly decreased after 48
hours GFR is significantly decreased after 48 hours
Summary of UUO and BUO
Pathophysiology
Obstructive Uropathy
Obstructive Nephropathy
Pathophysiology of Bilateral Ureteral Obstruction
Hemodynamic Effects
Tubule Effects Clinical Features
Acute
Renal Blood Flow ureteral and tubular pressures
pain
GFR azotemia
Medullary Blood Flow
reabsorption of Na, urea, water
Oliguria or anuria
Vasodilator PGs
Chronic
Renal Blood Flow medullary osmolarity
azotemia
GFR concentrating ability
hypertension
vasoconstrictor PGs
Structural damage; parenchymal atrophy
ADH-insensitive polyuria
renin-angiotensin pdn
transport fxn for Na,K, H
Hyperkalemic, hyperchloremic acidosis
Pathophysiology of Bilateral Ureteral Obstruction
Release of Obstruction
Slow in GFR (variable)
Tubular pressure Postobstructive diuresis
solute load per nephron (urea, NaCl)
Potential for volume depletion and electrolyte imbalance due to losses of Na, K, PO4, Mg and water
Natriuretic factors present
Consequences of urinary tract obstruction
• Reduced glomerular filtration rate
• Reduced renal blood flow (after initial rise)
• Impaired renal concentrating ability
• Impaired distal tubular function
• Nephrogenic diabetes insipidus
• Renal salt wasting
• Renal tubular acidosis
• Impaired potassium concentration
• Postobstructive diuresis
Progressive and permanent changes to the kidney occur Tubulointerstitial fibrosis Tubular atrophy and apoptosis Interstitial inflammation
Consequences of urinary tract obstruction
Diagnosis• History
– Pain, renal colic– Inability to void effectively– Alteration in pattern of micturition (anuria,
polyuria, nocturia)– Recurrent UTI– New-onset or poorly controlled hypertension– Polycythemia– Recent gynecologic or abdominal surgery
• History– Medication history
• Antihistamines, antipsychotics, antidepressants • Ethylene glycol, indinavir, methotrexate,
phenylbutazone, or sulfunamides• Methysergide or other natural-occurring
ergotamines– Occupational exposure history
• Textile manufacturers, shipyard workers, roofers or asbestos miners (retroperitoneal fibrosis)
• Textile workers, rubber manufacturing workers, leather workers, painters, hairdressers, drill press workers (bladder cancer)
Physical Examination Signs of dehydration and intravascular volume
depletion Peripheral edema, hypertension, signs of
congestive heart failure Palpable kidney or bladder Enlargement of pelvic organs (eg. Prostate,
uterus) Examination of external urethra for phimosis,
meatal stenosis
Normal kidney
Treatment and management Prehospital Care
Pulmonary edema Salt and water retention hypovolemia
Treatment and management Emergency department care
Investigate and begin treatment of potentially life-threatening complications Pulmonary edema Hypovolemia Urosepsis Hyperkalemia
Treatment and management• Overriding goal of treatment: reestablishment of
urinary flow– Transurethral bladder catheterization
• Diagnostic and therapeutic• No urine output = investigate upper tract
Treatment and management Large PVR = obstruction below the bladder
Fractionating urine removal (?) Christensen, et al. concluded that fractionating urine removal in
bladder obstruction is unjustified Hematuria and bladder spasm
Gould, et al. : hematuria correlated strongly with degree of bladder wall damage prior to relief of obstruction and not with rate of bladder emptying
Urine should be drained completely and rapidly from an obstructed bladder
Prolonged urine stasis only predisposes to UTI, urosepsis and renal failure
Treatment and management Calculi – most common causes of unilateral
ureteral obstruction 90% pass spontaneously (calculi <5.0-7.0 mm) Surgical drainage necessary if with unrelenting
pain, UTI, persistent obstruction, progressive loss of renal function
Position of stone determines preferred method of removal
Treatment and management Bilateral ureteral obstruction – always
asymmetric process mid to proximal ureter – percutaneous
nephrostomy Distal obstruction – cystoscopic placement of
ureteral stent Intrarenal obstruction secondary to crystals or
protein casts - hydration
Treatment and management Consultations
UROLOGIST – when transurethral catheter cannot provide adequate drainage and surgical drainage and removal of obstruction is necessary
NEPHROLOGIST – when emergent hemodialysis is necessary
Treatment and management Further Inpatient care
Decision to admit depends on the need for invasive surgical drainage procedure and complications of obstruction
Replacement of electrolyte disturbances Further Outpatient care
Depending on specific complications of obstruction, relief of bladder neck obstruction requires prompt follow-up care with a urologist for definitive therapy.
Prognosis With relief of obstruction
Reversible or irreversible damage? Obstruction NOT relieved
Complete or incomplete? Bilateral or unilateral? Presence or absence of infection
Summary UTO is an important urologic disorder and a
common cause of acute and chronic renal failure
Multiple causes, high clinical suspicion and acumen necessary
UTO is a potentially reversible process Prompt recognition Prompt treatment Prompt consultation/referral
Thank You