Acute urinary retention

• New onset inability to pass urine, which subsequently leads to pain and discomfort, with significant residual volumes
• Most common cause in men is BPH
• UTIs can cause the urethral sphincter to close, especially in those with already narrowed outflow tracts (e.g. BPH)
• Medications such as anticholinergics or spinal/epidural anaesthesia can affect innervation to the bladder
• Neurological causes - peripheral neuropathy, iatrogenic nerve damage during pelvic surgery, upper motor neurone disease (MS, PD)
• Clinical features:

  • Acute suprapubic pain
  • Inability to micturate (may pass small amounts)
  • Palpably distended bladder (at least 200ml to be palpable)
  • Any associated fevers, rigors or lethargy may suggest an infective cause
• Investigations:

  • DRE - enlarged prostate or constipation
  • Post void bladder scan
  • Urinalysis
• High Pressure Urinary Retention refers to the urinary retention causing such high intra-vesicular pressures that the anti-reflux mechanism of the bladder and ureters is overcome and ‘backs up’ into the upper renal tract leading to hydroureter and hydronephrosis, impairing the kidneys’ clearance levels.
• Patients with features of high pressure retention require an ultrasound to check for hydronephrosis - can cause renal scarring and CKD
• Patients with very high post-void volumes (arbitrarily >1L) or evidence of high pressure retention should be catheterised with a long-term catheter.
• Those with high post-void volumes should also have urine output monitored for post-obstructive diuresis - Excessive water and salt loss. Can worsen AKI.
• Management:

  • Immediate urethral catheterisation
  • Treatment of enlarged prostate e.g. tamsulosin
  • Long term catheter if features of high pressure retention
  • If no evidence of renal impairment, TWOC can be attempted
• Causes:

  • BPH (most common cause in men)
  • Other common obstructive causes - urethral strictures and prostate cancer
  • UTI - can cause urethral sphincter to close
  • Constipation
  • Severe pain
  • Medication - anti-muscarinics and spinal/epidural anaesthesia
  • Neurological
• Complications:

  • AKI
  • CKD
  • Urinary tract infections and stones due to urinary stasis