• Clinical science

Urinary retention


Urinary retention is the inability to voluntarily empty the bladder. The causes can be either mechanical (e.g., benign prostatic hyperplasia, tumors, urethral strictures) or functional (e.g., detrusor underactivity due to peripheral neuropathy, anticholinergic drugs). Patients with acute urinary retention (AUR) present with a sudden, painful inability to void and a tender, distended bladder on palpation. Patients with chronic urinary retention (CUR) are typically unable to void completely but do not experience pain. AUR is usually diagnosed clinically and is considered a urological emergency. Therefore, urgent bladder catheterization should precede diagnostics. These include renal function tests to assess for renal damage (obstructive nephropathy) and ultrasound of the kidneys, ureter, and bladder to identify the underlying cause and possible complications (e.g., hydroureteronephrosis). Further evaluation depends on the patient history and physical examination. Treating the underlying cause (e.g., alpha adrenergics and/or TURP for BPH) is essential to prevent recurrence and complications due to urinary retention, such as UTI, nephrolithiasis, and renal failure.


Mechanical obstruction

Functional obstruction


Clinical features

Acute urinary retention Chronic urinary retention
Clinical features
  • More common in men, esp. > 70 years of age
  • Sudden, painful inability to void despite having a full bladder
  • Suprapubic pain/discomfort; palpable bladder
  • Patient is restless and distressed.

Physical examination

  • Abdominal and pelvic examination: urethra (for discharge/meatal stenosis), prepuce (retractability), vaginal examination (evaluation for a pelvic mass)
  • Digital Rectal Exam (DRE): to evaluate prostate size and tenderness; look for a rectal mass or fecal impaction; assess sphincter tone.
  • Complete neurological examination



Subtypes and variants

Urethral stricture

  • Definition: narrowing of the urethra with possible restriction of urinary flow
  • Etiology
    • Traumatic or iatrogenic (instrumentation/catheterization)
    • Post-infectious (e.g., urethritis)
    • Congenital
    • Idiopathic
  • Clinical findings
    • Features of bladder outlet obstruction (straining to micturate, weak stream, dribbling)
    • Pollakiuria
    • Feeling of incomplete urination
    • Urinary retention
  • Diagnostics
  • Treatment
    • Urethral dilation: intermittent dilation of the urethra; can be curative in some cases
    • Internal urethrotomy: endoscopic transurethral approach; incision at 12 o'clock position to release strictures/scar tissue
    • Urethroplasty: open reconstruction with excision of the fibrotic urethra and reanastomosis ; indicated if urethrotomy fails
    • Permanent urethral stents: placed endoscopically; indicated in patients with short-length strictures



AUR is a urological emergency and urgent bladder catheterization should precede any further investigations. In doubtful cases, abdominal ultrasound should be performed first. In patients with postoperative AUR, diagnostic tests are usually not needed.

Laboratory studies


  • Ultrasound of the kidney, ureter, and bladder: indicated in all patients with urinary retention
    • AUR: bladder distended with > 400 mL of urine
    • CUR: post-void residue > 300 mL; bladder wall thickening (in chronic obstructive urinary retention)
    • In both: evaluate for hydroureteronephrosis (due to BOO); diagnose bladder calculi or BPH, if present
    • In bladder tamponade: blood clot visualized as an echogenic, mobile mass; often seen at the base of the bladder

Further investigations

AUR is an urological emergency and requires urgent bladder catheterization before any further investigations are performed!


Urgent complete bladder catheterization

In all patients with acute or acute on chronic urinary retention (before further diagnostics)

Treatment of the underlying cause

In all patients with acute or chronic urinary retention:

See posterior urethral valves, urethral trauma, and treatment of lower urinary tract obstruction in urinary tract obstruction for information on the management of other causative factors.


last updated 02/08/2019
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