Urological emergency · KIMS Secunderabad
Urinary Tract Obstruction — When Urine Cannot Drain and the Kidney Is at Risk
Urinary tract obstruction (UTO) is any condition that impedes the normal flow of urine from the kidney to the bladder and out through the urethra. The consequences of obstruction depend on its level (upper tract — renal pelvis or ureter — vs lower tract — bladder outlet or urethra), whether it is complete or partial, whether it is unilateral or bilateral, and how acutely it develops. Complete bilateral obstruction is a urological emergency — total anuria develops, and without drainage within hours, irreversible kidney damage and uraemic death follow. Partial unilateral obstruction may cause only a dull loin ache for weeks before being detected. The clinical presentation ranges from a minor incidental finding to a life-threatening emergency.
At KIMS, urinary tract obstruction is a condition that the urology and nephrology teams manage jointly — the urology team decompresses the obstruction (stenting or nephrostomy), and the nephrology team manages the AKI, electrolyte complications, and post-obstructive diuresis that follow relief of chronic obstruction.
Causes by level and age group
Upper tract — renal pelvis / UPJ
Common causes: UPJ obstruction (congenital) · Crossing vessel compression. Clue: Flank pain · Hydronephrosis on ultrasound. Emergency level: Elective management unless infected.
Ureteric
Common causes: Kidney stone (most common) · Ureteric stricture (post-stone, post-surgery, TB) · Extrinsic compression from tumour · Retroperitoneal fibrosis. Clue: Colicky loin-to-groin pain for stones · Silent for extrinsic causes. Emergency level: Emergency if infected (pyonephrosis).
Bladder outlet
Common causes: BPH (most common in men above 50) · Bladder neck contracture · Bladder tumour at the trigone. Clue: Slow stream · Urinary retention · Bilateral hydronephrosis if chronic.
Urethra
Common causes: Urethral stricture · Posterior urethral valve (PUV — male infants) · Phimosis. Clue: Reduced stream · Retention · PUV — neonatal presentation.
Acute presentations — urinary retention and bilateral obstruction
Acute urinary retention — the most urgent presentation
Acute urinary retention (AUR) — the sudden, painful inability to pass urine — is the most common acute urological emergency in men above 50. The patient presents with severe lower abdominal discomfort, a distended palpable bladder, and inability to void despite a strong urge. AUR is almost always caused by BPH in older men, triggered by a precipitating event: cold weather (alpha-adrenergic stimulation increases urethral tone), alcohol or large fluid intake, constipation, or medications (antihistamines, antidepressants, opioids — all have anticholinergic effects on the bladder). Treatment: immediate urethral catheterisation at KIMS, decompression of the bladder, and investigation of the underlying cause. BPH is then treated definitively (HoLEP, TURP, or medical therapy) once the acute episode resolves.
Bladder outlet obstruction — bilateral hydronephrosis and AKI
Urethral catheterisation immediately relieves bilateral hydronephrosis and AKI from this cause. Bladder drainage is both diagnostic and curative.
Bilateral ureteric obstruction from malignancy
Bilateral JJ stent insertion (retrograde, through the urethra and bladder under cystoscopy) or bilateral percutaneous nephrostomies (PCN) under ultrasound guidance. The choice depends on the level and severity of obstruction and the ability to pass a stent retrogradely past the obstruction.
Post-obstructive diuresis
After relief of bilateral chronic obstruction, the kidneys — which have been accumulating solute and unable to respond to ADH during the obstruction — produce a massive diuresis (1 to 2 litres per hour) as the pent-up urine is released. This diuresis can cause severe hypovolaemia, hypokalaemia, and hyponatraemia if fluid replacement is inadequate. At KIMS, post-obstructive diuresis is managed with IV fluid replacement matching 50 to 75% of urine output until the diuresis settles.
Investigation
Renal ultrasound — the first-line investigation. Identifies hydronephrosis (dilated collecting system from obstruction), the level of obstruction if visible, and bilateral vs unilateral involvement.
CT KUB (non-contrast) — for suspected ureteric stone — identifies stones, their size and position, and the degree of hydronephrosis above them.
CT abdomen with contrast — for suspected tumour, retroperitoneal fibrosis, or extrinsic ureteric compression — provides soft tissue detail.
Serum creatinine and eGFR — rising creatinine confirms functionally significant obstruction.
DTPA renogram — for chronic, partial obstruction — measures differential kidney function and drainage half-time, determining whether intervention is needed.
Book an Urgent Urology Assessment for Urinary Tract Obstruction at KIMS — 24/7 Emergency Decompression Available. Call 040-4488-5000
Frequently Asked Questions — Urinary Tract Obstruction
Hydronephrosis is the dilation of the renal pelvis and calyces — the collecting spaces within the kidney — caused by backed-up urine from an obstruction downstream. It is a radiological finding (seen on ultrasound or CT) that indicates something is blocking the free flow of urine. The obstruction may be at the UPJ, the ureter, the bladder outlet, or the urethra. Hydronephrosis itself is not a disease — it is a sign of an underlying obstruction that needs to be identified and treated. Mild hydronephrosis in a completely asymptomatic person may be a normal variant (physiological hydronephrosis) — the clinical context and the presence or absence of a cause determine significance.
Yes — complete or high-grade bilateral obstruction that is not relieved within hours to days causes progressive and eventually irreversible kidney damage. The back-pressure from the obstructed urine damages tubular cells and the glomerular apparatus — first functionally (reversible if the obstruction is relieved), then structurally (tubular atrophy and interstitial fibrosis — irreversible). Long-standing partial unilateral obstruction causes progressive loss of function in the obstructed kidney (detectable on DTPA renogram as reduced differential function) even without causing overt AKI. Prompt diagnosis and treatment of obstruction — even when the other kidney is functioning normally — is important to preserve the obstructed kidney's future function.
A kidney stone does not cause pain while it remains in the kidney — it is only when it migrates into the ureter and obstructs urine drainage that pain occurs. The pain of ureteric colic is caused by distension of the renal pelvis and ureter above the stone — the obstruction causes urine to back up under pressure, stretching the smooth muscle walls. The ureter and renal pelvis respond with intense peristaltic contractions attempting to push the stone down — these contractions generate the severe, colicky (waxing and waning) pain of renal colic. The pain radiates from the loin (as the kidney pelvis distends) to the groin and genitalia (as the stone approaches the bladder) — following the distribution of the ureteric innervation.
Post-obstructive diuresis is the large diuresis — often 1 to 3 litres per hour — that occurs after relief of bilateral urinary tract obstruction or bladder outlet obstruction. During the obstruction, solutes and water have accumulated in the body — sodium, urea, and fluid. When the obstruction is relieved, these accumulated solutes create an osmotic diuresis, driving massive urine output. Simultaneously, the tubules — which have been compressed and dysfunctional during the obstruction — have lost their ability to concentrate urine and conserve electrolytes normally. The result: rapid loss of sodium, potassium, and free water that, if not replaced, causes hypovolaemia, hypokalaemia, and potentially cardiovascular collapse. At KIMS, patients with post-obstructive diuresis receive IV fluid replacement (0.45% saline or alternating isotonic saline and 5% dextrose) matching 50 to 75% of urine output, with hourly electrolyte monitoring.
KIMS Secunderabad — Dr. K. V. R. Prasad (Chief Urologist, 28+ years, pioneer PCNL centre), 24/7 emergency ureteric stenting and percutaneous nephrostomy, stone surgery (RIRS and Mini-PCNL — all stone sizes), BPH surgery (HoLEP — no size limit), post-obstructive diuresis management in collaboration with nephrology. NABH and NABL accredited. Emergency line: 040-4488-5000.