Urinary retention

Question 1

Distinguish acute from chronic urinary retention

Answer 1

Acute

• Painful inability to void
• residual vol 300-1500ml (significant)

Chronic

• painless
• may still be voiding
• residual vol 300-400ml
• longstanding retention = significant bladder distension = results in bladder desensitisation = minimal discomfort
• sometimes present with overflow incontinence usually nocturnal

However, patients with chronic retention can also enter acute retention

Question 2

What are some common causes of urinary retention

Answer 2

Men = BPH, prostate cancer, urethral strictures

Women = pelvic masses, urethral stenosis, pelvic prolapse

Both = constipation (compression of urethra), UTI, neuro dysfunction eg. MS, recent surgery, drugs eg. antimuscarinics or spinal/epidural anaesthesia

Question 3

What is the definition of residual volume

Answer 3

the amount of urine left in the bladder after urination.

Postvoid residual volume of over 100ml, or over 1/3 of bladder capacity, is considered incomplete emptying.

This is measured via an Ultrasound Post Void Residual test.

Question 4

How is acute urinary retention commonly treated?

Answer 4

• immediate urethral catheterisation and record residual vol
• monitor for post-obstructive diuresis if large vol retention
• history, exams (abdo, ext genitalia, dre)
• urine dip, U&Es
• a-blocker in men (Tamsulosin)
• If there is no evidence of renal impairment, then trial without catheter
• TURP if this fails

Question 5

What is the difference between low pressure and high pressure chronic retention?

Answer 5

High pressure
- abnormal U&Es
(beware Hyperkalaemia)
- Hydronephrosis

Low pressure

• Normal renal function
• No Hydronephrosis

Question 6

What is a possible problem after catheterisation in chronic retention?

Answer 6

Post obstructive diuresis

• initial physiological off-loading of accumulated salt and water during chronic retention
• sometimes can become excessive and lead to dehydration or electrolyte imbalance
• monitor carefully and give oral fluid replacement (rarely need saline IVI)

Question 7

What is the treatment for chronic retention?

Answer 7

• catheterise with long term catheter and record residual vol
• history, exams, urine dip, U&Es
• admit overnight and monitor for post-obstructive diuresis

High pressure = no TWOC without a TURP

Low pressure =

• TURP (but risk of detrusor failure and having to do long-term catheter)
• Intermittent self-cath (instead of TURP due to TURP risks)

Question 8

Clinical features of urinary retention

Answer 8

• acute suprapubic pain
• inability to micturate
• infection = fever, rigors, lethargy
• On abdo = palpable distended bladder and suprapubic tenderness

Question 9

Investigations for urinary retention

Answer 9

DRE to assess for prostate enlargement or constipation

post-void bedside bladder scan shows vol of retained urine

Routine bloods

High pressure retention requires US to assess for hydronephrosis