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 renal pelvis 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 – – – • Sex – – • No data available in unselected populations 20-35% prevalence in large survey among elderly men 3.8% (adults); 2.0% (children) postmortem examinations 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 Bladder neck obstruction Posterior urethral valves CONGENITAL Ureteropelvic junction narrowing or obstruction Ureterovesical Ureterocele junction narrowing or obstruction and reflux Ureterocele Damage to S2- Stricture 4 Retrocaval ureter VUR Anterior urethral valves Meatal stenosis 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 Retroperitoneal fibrosis trauma Aortic aneurysm Uterine leiomyomata Carcinoma of uterus, prostate, bladder, colon, rectum lymphoma Pelvic inflammatory disease, endometriosis Accidental surgical ligation trauma 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-PGC) Kf- glomerular ultrafiltration coeffecient related to the surface area and permeability of the capillary membrane PGC- glomerular capillary pressure. Influenced by renal plasma flow and the resistance of the afferent and efferent arterioles PT- Hydraulic pressure of fluid in the tubule P- the oncotic pressure of the proteins in the glomerular capillary and efferent arteriolar blood 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 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 ureteral and tubular pressures pain Acute Renal Blood Flow GFR Medullary Blood Flow azotemia reabsorption of Na, urea, water Oliguria or anuria Vasodilator PGs Chronic Renal Blood Flow GFR vasoconstrictor PGs medullary osmolarity azotemia concentrating ability hypertension Structural damage; parenchymal atrophy renin-angiotensin pdn transport fxn for Na,K, H ADH-insensitive polyuria Hyperkalemic, hyperchloremic acidosis Pathophysiology of Bilateral Ureteral Obstruction Release of Obstruction Slow in GFR (variable) Tubular pressure solute load per nephron (urea, NaCl) Natriuretic factors present Postobstructive diuresis Potential for volume depletion and electrolyte imbalance due to losses of Na, K, PO4, Mg and water 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 Consequences of urinary tract obstruction Progressive and permanent changes to the kidney occur Tubulointerstitial fibrosis Tubular atrophy and apoptosis Interstitial inflammation 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 (?) Hematuria and bladder spasm Christensen, et al. concluded that fractionating urine removal in bladder obstruction is unjustified 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