Obstructive uropathy

Obstructive uropathy is a structural or functional blockage of urinary flow, causing a back-up of urine (hydronephrosis) and potential kidney damage.

• Without prompt relief, obstruction can cause permanent kidney damage or life-threatening renal failure; however, it’s a reversible cause of acute kidney injury when recognized (classic in infant boys with PUV and older men with BPH).

• Flank pain (if upper tract, e.g., stone) or lower abdominal/bladder distension (if lower tract); poor urinary stream, straining, or urinary retention (e.g., BPH, PUV). May have hematuria (stone) or UTI symptoms. Severe bilateral obstruction → oliguria and rising creatinine.
• Pediatric causes: Posterior urethral valves (PUV) in infant boys (congenital bladder outlet obstruction), ureteropelvic junction (UPJ) obstruction (congenital hydronephrosis), and neurogenic bladder (e.g., spina bifida).
• Adult causes: Benign prostatic hyperplasia (BPH) – most common, ureteral calculi (kidney stones), tumors (prostate, bladder, cervical, etc.), urethral strictures, pelvic masses, and retroperitoneal fibrosis.

1. In any acute kidney injury, rule out post-renal obstruction: check for bladder distension (bladder scan, catheter) and perform renal ultrasound for hydronephrosis.
2. Remember that unilateral obstruction (normal other kidney) may not raise creatinine; bilateral or single-kidney obstruction is needed to cause acute renal failure.

1. Promptly relieve the obstruction: e.g., insert a Foley catheter for bladder outlet obstruction, or place a nephrostomy tube/ureteral stent for upper tract obstruction.
2. Treat the underlying cause: endoscopic valve ablation for PUV, stone removal (lithotripsy or ureteroscopy), prostate management (medications or TURP for BPH), or surgical resection of tumors/masses.
3. Manage complications: treat UTIs with antibiotics, and monitor for post-obstructive diuresis (aggressive IV fluids and electrolyte monitoring if high output).

• A palpable bladder in a newborn boy with poor urine output = think PUV (posterior urethral valves).
• After relieving a prolonged obstruction, watch for post-obstructive diuresis (massive urine output) and replace fluids/electrolytes.
• Unexplained rise in creatinine? Always consider a post-renal cause — obstructive uropathy is one of the most easily reversible causes of AKI.

• Post-obstructive diuresis: after decompression, high urine output can cause dehydration/electrolyte imbalance; monitor urine output closely.
• Bilateral obstruction (or obstruction of a solitary kidney) can cause acute kidney injury – a urologic emergency requiring urgent drainage.
• Urinary stasis from obstruction → recurrent UTIs and stones; chronic obstruction leads to permanent renal scarring if untreated.

1. Suspect obstructive uropathy → assess bladder (palpation/bladder scan) and do renal ultrasound for hydronephrosis.
2. If obstruction confirmed → decompress immediately (e.g., Foley catheter, nephrostomy).
3. Find and address cause: imaging (CT, cystoscopy, VCUG) to identify level/cause → definitive treatment (stone removal, valve ablation, prostate surgery, etc.).

• Newborn boy with a distended bladder, weak urinary stream, and bilateral hydronephrosis → posterior urethral valves (congenital obstruction).
• Flank pain radiating to the groin with hematuria; ultrasound shows hydronephrosis → ureteral stone causing obstruction.