Hello FY1s this is a quick to thinking about urinary retention mainly focusing on acute retention.

Acute
- Painful inability to void urine with a palpable bladder, often occurs over a number of hours. Medical emergency, patients are often very distressed.

Chronic
- Inability to completely empty the bladder after voiding, occurs gradually over weeks to months, painless palpable bladder after voiding

How much is too much?
A bladder volume of >300mls on a bladder scan would justify catheterisation but if a patient is symptomatic with less than this volume then catheterisation must be considered as bladder scans may not always be accurate, e.g in obese patients, ascites,

Causes
The most common cause of urinary retention is benign prostrate hypertrophy (BPH) which can lead to both acute and chronic retention of urine. Patients may already have known BPH or may give a history suggestive of this such as increased urinary frequency, incomplete voiding, hesitancy,  nocturne or terminal dribbling.

Acute
  • Spontaneous progression of BPO, 
  • Constipation (very common in geriatric patients), 
  • Alcohol excess
  • Post op
  • UTI
  • Post partum
  • Drugs - antimuscarinic drugs, sympathomimetics, tricyclic antidepressants
  • Bladder stones
Chronic 
  • Detrusor inactivity
  • Neurogenic causes - MS
  • Pelvic surgery
  • Abnormal anatomy -urethral stricture, prostate cancer, BPH
How to recognise

History 
An important starting point for any diagnosis in medicine not just acute retention, is the patient in pain? Do they have an urge to empty their bladder? Have they had symptoms of bladder outflow obstruction previously?

Examination
  • Can I feel a palpable, distended or percussible bladder? 
  • PR - enlarged or irregular prostrate? faecal impaction
  • Bloods - important to check renal function and inflammatory marker 
  • Bladder scan 
Treatment
  • 1st step is usually to catheterise - particularly in acute retention! 
  • Early catheterisation in acute retention can provide instant relief of pain.
  • If retention is due to BPH then an alpha blocker can be started prior to a trail without catheter. Patients may be referred to Urology for consideration of a Transrectal resection of the prostate.
  • Looking for a cause of retention can help prevent future episodes - e.g stopping culprit medications, laxatives for constipation
Complications of urinary retention
  • Renal failure 
  • UTI 
  • Post decompression haematuria 
  • Pathological diuresis - urine output of >200ml/hour or postural hypotension (drop of 20mmHg)
  • Electrolyte abnormalities
References and further reading:
https://bnf.nice.org.uk/treatment-summary/urinary-retention.html

Dr Emma-James Garden​ FY3