Acute Urinary Retention

Acute urinary retention is the sudden painful inability to voluntarily empty a distended bladder.

It is a urological emergency requiring prompt bladder decompression.

Major causes include:

• Benign prostatic obstruction
• Urethral stricture
• Prostate cancer
• Bladder neck obstruction
• Urethral or bladder stone
• Severe constipation or faecal impaction
• Acute prostatitis
• Neurological disease
• Spinal cord compression or cauda equina syndrome
• Postoperative retention
• Anticholinergic, sympathomimetic or opioid medication
• Clot retention

In older men, benign prostatic enlargement is the commonest cause, but urinary retention should never automatically be attributed to BPH without considering neurological, malignant and urethral pathology.

Typical presentation:

• Severe suprapubic pain
• Inability to void
• Increasing urinary urgency
• Palpable or percussible distended bladder

Patients with neurological disease, diabetes or chronic retention may have surprisingly little pain despite a very large bladder.

Ask about:

• Previous LUTS
• Weak urinary stream
• Straining
• Previous urethral instrumentation
• Haematuria
• Fever
• Constipation
• New neurological symptoms
• New medications

Perform:

• Abdominal examination
• External genital examination
• Digital rectal examination when appropriate
• Lower limb neurological examination if neurological disease is possible
• Saddle sensation and anal assessment when cauda equina syndrome is suspected

Blood at the urethral meatus after trauma raises concern for urethral injury and changes the catheterisation pathway.

The diagnosis is usually clinical.

Bladder scan or ultrasound: confirms urinary retention and estimates bladder volume when diagnosis is uncertain.

Check:

• Urinalysis
• Urine culture if infection suspected
• Creatinine and electrolytes
• Full blood count when infection or bleeding is present

PSA should not be interpreted during acute retention as a cancer diagnostic test because urinary retention can temporarily increase PSA.

Renal ultrasound is particularly useful when there is:

• Renal impairment
• Chronic LUTS
• Recurrent retention
• Suspected upper tract obstruction

Immediate treatment is bladder drainage.

Urethral catheterisation

Use appropriate aseptic technique and adequate urethral lubrication.

A typical first catheter is:

16 to 18 Fr Foley catheter

A larger catheter may be required for haematuria with clot retention.

Do not repeatedly force a catheter against resistance.

If significant resistance occurs, consider:

• Urethral stricture
• False passage
• Enlarged obstructing prostate
• Urethral injury

Use flexible cystoscopic catheter placement or suprapubic drainage when appropriate.

Suspected traumatic urethral injury

Do not perform repeated blind catheterisation.

Obtain retrograde urethrography or cystoscopic assessment and establish controlled urinary drainage.

Failed urethral catheterisation

Place a suprapubic catheter when the bladder is sufficiently distended and there is no contraindication to suprapubic access.

Rapid versus gradual decompression

The bladder can be drained completely.

Routine intermittent clamping to achieve gradual decompression is unnecessary.

Observe for:

• Transient haematuria
• Hypotension
• Post obstructive diuresis

Post obstructive diuresis

Suspect clinically significant post obstructive diuresis when urine output exceeds approximately:

• 200 mL/hour for at least 2 consecutive hours

or

• 3 litres over 24 hours

Monitor:

• Urine output
• Sodium
• Potassium
• Magnesium
• Creatinine
• Volume status

Replace only a proportion of urinary losses, commonly approximately 50% to 75%, using appropriate IV or oral fluid while avoiding perpetuation of the diuresis through excessive replacement.

BPH associated retention

Start an alpha blocker before trial without catheter.

A practical regimen is:

Tamsulosin 0.4 mg orally once daily

Warn about:

• Dizziness
• Postural hypotension
• Ejaculatory dysfunction

Perform trial without catheter after the acute precipitating cause has settled, commonly after several days of alpha blockade.

Failure of repeated trial without catheter should prompt consideration of definitive outlet surgery rather than repeated prolonged catheter dependence.

Recurrent retention is an important indication for surgical treatment of bladder outlet obstruction.