PassFinals
Renal & Urology

Urinary Retention

Urinary retention is failure to empty the bladder: acute retention is usually painful and needs prompt drainage, while chronic retention may be painless but can cause overflow, hydronephrosis and acute kidney injury, so the cause, residual volume and upper-tract risk determine urgency.

In a nutshell

Acute retention is usually painful and needs prompt catheterisation; chronic retention may be painless but can cause overflow, hydronephrosis and AKI. Scan the bladder, check renal function and urine, treat the cause, use an alpha-blocker before trial without catheter in men, monitor post-obstructive diuresis and always consider cauda equina in painless retention with neurological red flags.

Classic presentation

An older man with poor stream and nocturia suddenly develops painful inability to void and a tender suprapubic bladder; drain promptly, record the residual and arrange an alpha-blocker before a planned trial without catheter.

Key points

  • Acute retention is painful; chronic retention is often painless and may present with overflow dribbling or renal impairment.
  • Immediately catheterise acute retention and record the drained volume; escalate difficult or traumatic catheterisation.
  • In men, offer an alpha-blocker before catheter removal and arrange a planned trial without catheter.
  • Chronic retention with a residual over 1 litre or a palpable/percussible bladder needs creatinine and upper-tract imaging; catheterise if renal function is impaired or hydronephrosis is present.
  • Monitor for post-obstructive diuresis after large-volume or high-pressure decompression.
  • Painless retention with saddle anaesthesia, bilateral leg symptoms or severe back pain needs same-day cauda-equina assessment and imaging, not simple discharge.

First-line investigation

Bladder scan and abdominal examination, with drained-volume recording, renal function/electrolytes, urinalysis and upper-tract imaging when chronic/high-pressure retention or AKI risk is present.

Management

Drain the bladder and assess danger

  • Promptly catheterise acute retention, record the drained volume and check for AKI, infection, hyperkalaemia, difficult catheterisation and neurological red flags.1,4,9

Find the cause and the renal risk

  • Use residual volume, renal function, urinalysis and cause-directed examination; chronic retention over 1 litre or with a palpable bladder needs upper-tract imaging and creatinine assessment.1,4,2

Prevent recurrence in presumed prostatic obstruction

  • In men, offer an alpha-blocker before catheter removal and arrange a planned trial without catheter; recurrent failure or non-prostatic causes need urology review.1,3

Monitor high-pressure drainage and neurological emergencies

  • After large-volume or high-pressure decompression, monitor urine output, fluid balance, renal function and electrolytes; same-day emergency assessment is required when cauda-equina features accompany retention.8,10,5,6

Definitively treat the obstruction or bladder dysfunction

  • Arrange urological follow-up for recurrent, complicated or unexplained retention and choose outlet treatment, intermittent catheterisation, long-term catheterisation or neuro-urological care according to the cause and renal risk.1,2,7

Exam traps

  • Do not delay catheterisation in acute retention for a bladder scan or routine blood tests.
  • Painless retention with neurological signs is not benign overflow; treat suspected cauda equina as an emergency.
  • A large painless residual can be high-pressure chronic retention and cause obstructive AKI.
  • Record the drained volume and monitor for post-obstructive diuresis after major decompression.
  • Offer an alpha-blocker before removing the catheter in men, but a failed trial needs urological follow-up rather than repeated blind removal.
  • Do not take a PSA result during acute retention or infection at face value.
  • If urethral catheterisation is difficult or traumatic, stop repeated attempts and seek specialist/suprapubic drainage.

Illustrations

Marked bladder distension in urinary retentionClinical photograph showing a large smooth suprapubic swelling caused by a markedly distended bladder in urinary retention.Frivadossi, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. NICE CG97, Lower urinary tract symptoms in men: management (Current NICE male LUTS and retention pathway: immediate catheterisation for acute retention, alpha-blocker before catheter removal, chronic-retention imaging/creatinine and catheterisation thresholds; published 25 June 2010)Published 25 Jun 2010
  2. NICE CKS, Retention of urine (NICE CKS assessment, catheter, differential and follow-up anchor; direct access may require NHS or institutional login)
  3. BNF, Lower urinary tract symptoms, alpha-adrenoceptor blockers and medicines affecting bladder emptying (Current UK prescribing, contraindication, interaction, postural-hypotension and retention-risk checks)
  4. NICE NG148, Acute kidney injury: prevention, detection and management (Current NICE obstruction, urgent ultrasound, upper-tract referral, renal-replacement and AKI-monitoring pathway; published 18 December 2019)Published 18 Dec 2019
  5. NICE NG127, Suspected neurological conditions: recognition and referral (Current NICE cauda-equina recognition and referral guidance, with the associated NHS interactive pathway updated June 2025)Published 1 May 2019
  6. NICE CG148, Urinary incontinence in neurological disease (Current NICE neurological bladder pathway, including urgent referral for urinary changes due to new/progressing neurological disease and renal-risk monitoring)Published 22 Aug 2012
  7. NHS Borders Right Decisions, Urinary catheterisation policy for adults (UK NHS catheterisation and trial-without-catheter practice, including residual-volume recording, difficult catheterisation escalation and local alpha-blocker practice)
  8. Norfolk and Norwich University Hospitals NHS, High-pressure chronic retention and post-obstructive diuresis procedure (UK NHS procedure for large-volume chronic retention, drained-volume recording and close urine, fluid and electrolyte monitoring after decompression)
  9. NICE NG253, Suspected sepsis in people aged 16 or over (Current adult sepsis recognition, sampling, treatment and escalation pathway; published 19 November 2025)Published 19 Nov 2025
  10. NICE CG174, Intravenous fluid therapy in adults in hospital (Current NICE 5-R fluid assessment and reassessment principles for post-obstructive fluid/electrolyte management)Published 10 Dec 2013

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.