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