Acute urinary retention
Drain the bladder — then work out why it filled. Confirm with a bladder scan, catheterise and record the residual, check the kidneys, and look for the cause. Never forget the neurological causes, especially cauda equina. Built for revision, not live patient decisions.
Settle them, and check the basics
drain · documentRed flags — what each should make you think
Painless retention in a man with a big residual volume and a raised creatinine is chronic high-pressure retention. Keep the catheter in, watch for a big diuresis, and don't send them home with a trial without catheter.
First actions
- 📟Bladder scan
- 🩺Catheterise
- 🩸U&E
- UOHourly urine output
- 🧪Urine dip + culture
- 🦵Neuro screen
Understand the patient — the cause
why did it happen?Common causes
- Benign prostatic enlargement (most common in men)
- Drugs — anticholinergics, opioids, antihistamines, decongestants, tricyclics, anaesthesia
- Constipation
- Infection (UTI, prostatitis)
- Post-operative (pain, anaesthesia, immobility)
- Clot retention (haematuria)
- Neurological — cauda equina, MS, spinal cord injury, diabetic neuropathy
- Urethral stricture, prostate cancer, pelvic masses (women)
After the catheter
- Residual over 1 litre suggests a chronic component — higher risk of post-obstructive diuresis
- Post-obstructive diuresis (urine output above about 200 mL/h): monitor fluid balance and U&E; replace losses with IV fluids if the patient becomes dry (not mL for mL)
- BPH: start tamsulosin and arrange a trial without catheter after 2–3 days (if creatinine normal and no high-pressure retention)
- Treat constipation; stop culprit drugs
Work A–E — assess and act as you go
The diagnoses you must not miss
tap to open eachWhat points toward it, what would rule it in, and how to manage it.
Back pain, bilateral sciatica, saddle anaesthesia, bowel changes.
Emergency MRI.
Spinal surgery. See the cauda equina page.
Painless, large residual (often over 1 L), raised creatinine, hydronephrosis, nocturnal enuresis.
U&E, renal USS.
Long-term catheter, monitor diuresis, urology; no early trial without catheter.
Retention with visible haematuria and clots.
Clinical.
Three-way catheter, bladder washout, continuous irrigation; urology. See the haematuria page.
Fever, rigors, hypotension with retention.
Cultures, lactate.
Drain the bladder, sepsis bundle, IV antibiotics.
Investigate — what to order, when, and what it tells you
test with a question in mindBladder scan
Bloods
Urine
Imaging
How the plan comes together
disposition · handoverhome with catheter
Simple BPH retention, normal renal function, no infection: catheter, tamsulosin, trial without catheter in 2–3 days, urology follow-up.
admit
AKI, high-pressure retention, diuresis, clot retention, sepsis, neurological cause.
Hand over: residual volume, creatinine, urine output, cause.
Scan, catheterise, record the residual, check the creatinine — and always screen for a neurological cause. Watch for the diuresis afterwards. Nicely done getting here.
Clerking template
copy or downloadAcute urinary retention — documentation structure
A structure and prompt list to help you document and think systematically. It is not a completeness check and cannot guarantee nothing is missed — use your trust's own proforma, your seniors, and your clinical judgement.
Test yourself
active recallCover the answer, say it out loud, then reveal. Retrieval beats re-reading.
0 / 10 knownFrequently asked questions
quick answersWhat are the red flags for acute urinary retention?
- Back pain, saddle numbness, bilateral leg symptoms — think cauda equina
- Painless retention, huge volume, AKI — think chronic high-pressure retention
- Visible haematuria with clots — think clot retention
- Fever, rigors — think urosepsis
- Urine output above 200 mL/h after draining — think post-obstructive diuresis
- Woman with retention — think pelvic mass / neuro cause
What is the initial management of acute urinary retention?
- Bladder scan — confirm retention
- Catheterise — aseptic technique; record the residual volume drained in the first 15 min
- U&E — AKI from obstruction
- Hourly urine output — if large residual or AKI
- Urine dip + culture — infection
- Neuro screen — back, saddle, bowels, legs
Always alongside senior support and your local guideline.
What diagnoses must you not miss in acute urinary retention?
- Cauda equina syndrome — retention + back
- High-pressure chronic retention — AKI · hydronephrosis
- Clot retention — haematuria
- Urosepsis — fever · retention
Open each one in the must-not-miss section for what points toward it, how to rule it in, and how to manage it.
What investigations should a junior doctor order for acute urinary retention?
- Bladder scan — Confirms retention.
- Bloods — AKI; repeat if large diuresis.
- Urine — Infection.
- Imaging — If AKI or high-pressure retention.
Admit or discharge: how is the plan decided for acute urinary retention?
- Home with catheter — Simple BPH retention, normal renal function, no infection: catheter, tamsulosin, trial without catheter in 2–3 days, urology follow-up.
- Admit — AKI, high-pressure retention, diuresis, clot retention, sepsis, neurological cause.
Is there a clerking template for acute urinary retention?
Yes — there is a clerking template for acute urinary retention on this page, structured as presenting complaint, red flags asked, history, examination (A–E), investigations, differentials, plan and escalation. You can copy it or download it as a Word document. Jump to the template.
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