Urinary tract overlap — urology

Infected obstructed kidney and urosepsis

Overview and approach

Urinary obstruction with infection is a source-control emergency, not simple renal colic.

Definition: an obstructed kidney (usually a ureteric stone; also tumour, stricture, clot) with signs of urinary tract infection and/or anuria is a urological emergency (1)(2).
Why it matters: antibiotics alone do not reliably sterilise an obstructed system; patients who are not drained have higher mortality (2). Sepsis from an infected obstructed system can progress to shock within hours.

Assessment and clinical features

Fever/rigors, flank pain, vomiting, hypotension, urine output and organ dysfunction; vulnerable patients may lack fever.

Features: loin pain with fever or rigors, vomiting, tachycardia, hypotension, reduced urine output, confusion in the elderly. Known stone, recent instrumentation, solitary kidney or immunosuppression raise risk.
Look for SIRS/sepsis criteria and organ dysfunction; check urine output.

Differentials and investigations

Blood/urine cultures, renal/electrolytes, lactate where indicated and urgent imaging; antibiotics must not wait for all results.

Differentials: simple pyelonephritis (no obstruction), uncomplicated renal colic, ruptured AAA, appendicitis, pelvic inflammatory disease, ectopic pregnancy, other sepsis sources.
Bloods/urine: urinalysis and culture, blood cultures if febrile (> 38 C) or SIRS/sepsis, creatinine/electrolytes/eGFR, calcium, urate, FBC, CRP, and a clotting screen if percutaneous intervention is likely (2).
Imaging: urgent imaging (non-contrast CT KUB or ultrasound) to confirm obstruction and level; do not delay antibiotics or drainage for results (1)(2).

Management and follow-up

Resuscitation, local-protocol IV antibiotics and immediate urology involvement for urgent drainage by stent or nephrostomy.

Resuscitate (sepsis bundle), take cultures and start broad-spectrum IV antibiotics immediately per local protocol; re-evaluate against culture results (EAU: strong recommendation) (1).
Urgent decompression: retrograde ureteric stent or percutaneous nephrostomy; EAU rates them as equally effective, so choose whichever is fastest and safest locally. BAUS standard: drain within a maximum of 12 hours, sooner if unwell (1)(2). Delays are associated with worse outcomes, and hospital-wide pathways have shortened time to decompression (3)(4).
Collect urine for culture again after decompression. Delay definitive stone treatment until sepsis has resolved and a full antibiotic course is completed (1).
Follow-up: monitor creatinine and urine output (post-obstructive diuresis), ICU if shocked, then definitive stone management (ureteroscopy, ESWL, PCNL) and metabolic stone work-up (see Renal colic and urinary tract stones).

Red flags and clinical pearls

Sepsis, anuria, solitary kidney or bilateral obstruction needs urgent escalation. Antibiotics alone may not control an infected obstructed system.

Fever plus a stone on imaging = obstructed infected system until proven otherwise.
Nephrostomy vs stent: no proven superiority; stents are tolerated worse (stent symptoms), nephrostomy needs IR availability and a clotting screen (1)(2).
Elderly, diabetic, immunosuppressed and pregnant patients may present with minimal fever.
Viva: why antibiotics alone fail, the two drainage options, when to treat the stone.

References

Last updated from Sen’s notes on 9 October 2026.