Overview
Acute Urinary Retention
Topic Overview
Summary
Acute urinary retention (AUR) is the sudden inability to pass urine despite a full bladder. It is a urological emergency that is painful and distressing. The most common cause in men is benign prostatic hyperplasia (BPH). Other causes include constipation, drugs (anticholinergics, opioids), urethral stricture, and neurological conditions. Treatment is urgent bladder decompression via urethral or suprapubic catheterisation. High-pressure chronic retention with renal impairment requires careful monitoring during decompression.
Key Facts
- Presentation: Painful inability to void with palpable/percussible bladder
- Most common cause: BPH in men; pelvic organ prolapse in women
- Treatment: Urgent catheterisation (urethral or suprapubic)
- Caution: High-pressure retention — monitor urine output and renal function
- Alpha-blockers: Improve chance of TWOC success
Clinical Pearls
Always check post-void residual if chronic retention suspected
High-pressure chronic retention may present painlessly with overflow incontinence and renal failure
Consider spinal cord pathology if lower limb weakness, sensory level, or faecal incontinence
Why This Matters Clinically
AUR is common and easily treated with catheterisation. Missing high-pressure retention or neurological causes can have serious consequences.
Visual Summary
Visual assets to be added:
- Causes of urinary retention diagram
- Catheterisation technique
- TWOC algorithm
- High vs low pressure retention comparison
Epidemiology
Incidence
- 3-7 per 1,000 men/year (over 45)
- Increases with age
- Less common in women
Demographics
- Men over 60 (BPH)
- Women (less common — prolapse, post-operative)
Causes
Men:
| Cause | Notes |
|---|---|
| BPH | Most common |
| Prostate cancer | |
| Urethral stricture | |
| Phimosis |
Women:
| Cause | Notes |
|---|---|
| Pelvic organ prolapse | Cystocele |
| Pelvic mass | Fibroid, ovarian cyst |
| Post-operative |
Both:
| Cause | Notes |
|---|---|
| Drugs | Anticholinergics, opioids, antihistamines |
| Constipation | Common precipitant |
| UTI | |
| Neurological | Spinal cord lesion, cauda equina, MS |
| Post-operative | Especially after surgery/anaesthesia |
Pathophysiology
Mechanism
- Bladder outlet obstruction (BOO) prevents emptying
- Bladder distends
- Detrusor muscle fails
- Unable to void
Types
| Type | Features |
|---|---|
| Acute retention | Sudden, painful, unable to void |
| Chronic retention | Gradual, painless, large residual volumes |
| High-pressure chronic | Transmitted back-pressure → hydronephrosis, renal impairment |
| Low-pressure chronic | Bladder failure, large residual, no renal impairment |
High-Pressure Chronic Retention
- Back-pressure on ureters and kidneys
- Hydronephrosis
- Post-obstructive diuresis after catheterisation
- Electrolyte disturbance
Clinical Presentation
Symptoms
Signs
Red Flags
| Finding | Significance |
|---|---|
| Leg weakness/numbness | Spinal cord/cauda equina |
| Faecal incontinence | Cauda equina |
| Renal impairment | High-pressure retention |
| Large residual (over 1L) | Risk of post-obstructive diuresis |
Inability to pass urine
Common presentation.
Suprapubic pain (acute)
Common presentation.
May be painless (chronic)
Common presentation.
Lower urinary tract symptoms (LUTS) — frequency, hesitancy, poor stream
Common presentation.
Overflow incontinence (chronic)
Common presentation.
Clinical Examination
Abdominal
- Palpable bladder (may rise to umbilicus)
- Dull to percussion suprapubically
- Tenderness (acute)
Genitalia
- Phimosis
- Meatal stenosis
- Urethral discharge
Digital Rectal Examination
- Prostate size, nodularity (cancer)
- Anal tone (neurological)
Neurological
- Lower limb power, sensation
- Perineal sensation (saddle area)
Investigations
Bedside
- Bladder scan — confirms retention, measures volume
Blood Tests
| Test | Purpose |
|---|---|
| U&E, creatinine | Renal function (high-pressure retention) |
| eGFR | Baseline |
| PSA | If prostate abnormal (NOT in acute infection) |
Urine
- Dipstick
- MSU (infection)
Imaging
| Modality | Indication |
|---|---|
| Renal USS | If renal impairment — hydronephrosis |
| CT urogram | If stone or malignancy suspected |
Classification & Staging
By Duration
| Type | Features |
|---|---|
| Acute | Sudden, painful |
| Chronic | Gradual, painless, large residual |
| Acute-on-chronic | Acute decompensation of chronic |
By Pressure (Chronic)
| Type | Renal Function |
|---|---|
| High-pressure | Impaired |
| Low-pressure | Normal |
Management
Immediate — Catheterisation
| Method | Notes |
|---|---|
| Urethral catheter | First-line; 14-16 Fr |
| Suprapubic catheter | If urethral fails, urethral trauma, stricture |
Technique
- Aseptic technique
- Local anaesthetic gel
- Advance until urine drains
- Inflate balloon with sterile water (10mL)
Post-Catheterisation
Record residual volume:
- Over 1L: Risk of post-obstructive diuresis
Monitor if high volume or renal impairment:
- Hourly urine output
- Daily U&E
- IV fluids if polyuric
Trial Without Catheter (TWOC)
| Timing | Notes |
|---|---|
| 48-72 hours | After starting alpha-blocker |
| Alpha-blocker | Tamsulosin 400mcg OD — improves success |
| Success rate | 40-50% first TWOC |
If TWOC Fails
- Re-catheterise
- Urology referral for long-term management
- Options: TURP, long-term catheter, clean intermittent self-catheterisation
Treat Underlying Cause
- Treat constipation
- Stop precipitating drugs
- Treat UTI
Complications
Of Retention
- Renal impairment
- UTI
- Bladder damage (prolonged retention)
Of Catheterisation
- UTI (CAUTI)
- Urethral trauma
- False passage
- Haematuria
Post-Obstructive Diuresis
- Large volume urine output after decompression
- Electrolyte disturbance (hyponatraemia, hypokalaemia)
- Requires IV fluid replacement
Prognosis & Outcomes
TWOC Success
- 40-50% first attempt
- Higher with alpha-blockers
Long-Term
- Many need definitive surgery (TURP)
- Some require long-term catheterisation
Evidence & Guidelines
Key Guidelines
- NICE NG131: Lower Urinary Tract Symptoms in Men
- EAU Guidelines on Non-Neurogenic Male LUTS
Key Evidence
- Alpha-blockers improve TWOC success
- Early TWOC (48-72h) is effective
Patient & Family Information
What is Urinary Retention?
Urinary retention is when you cannot empty your bladder, even though it is full. This is often caused by an enlarged prostate in men.
Symptoms
- Unable to pass urine
- Pain in the lower tummy
- Feeling like you need to go but can't
Treatment
- A tube (catheter) to drain the bladder
- Medication to help the bladder empty
- Sometimes surgery is needed
Resources
References
Primary Guidelines
- NICE. Lower Urinary Tract Symptoms in Men: Management (NG131). 2019. nice.org.uk
Key Reviews
- Selius BA, Subedi R. Urinary retention in adults: evaluation and initial management. Am Fam Physician. 2008;77(5):643-650. PMID: 18350761
- Emberton M, et al. Acute urinary retention in men. BMJ. 2017;358:j3756. PMID: 28830957