- Clinical science
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.
Brief overview of bladder control
- The frontal lobe cortex has an inhibitory effect on the pontine micturition center and an excitatory effect on the urethral sphincter (voluntary control of micturition).
- The central micturition center lies in the pons (brain stem) and controls the sympathetic and parasympathetic nerve supply of the bladder and urethra.
- T12–L2: sympathetic bladder innervation (via the hypogastric nerve; α and β adrenergic receptors) → detrusor relaxation and increased urethral sphincter tone (bladder filling phase)
- S2–S4: parasympathetic innervation (via the pelvic splanchnic nerves; muscarinic receptors) → detrusor contraction and relaxation of the urethral sphincter (voiding phase)
- The pudendal nerve (S2–S4) send afferent impulses from the bladder to the brain during bladder filling/voiding.
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|Acute urinary retention||Chronic urinary retention|
- Definition: narrowing of the urethra with possible restriction of urinary flow
- Traumatic or iatrogenic (instrumentation/catheterization)
- Post-infectious (e.g., )
- Clinical features
- 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. If the diagnosis is uncertain, abdominal ultrasound/bladder scan should be performed first to assess bladder volume. In patients with postoperative AUR, further investigations are usually not needed.
- Urinalysis and culture: indicated in all patients with urinary retention; evaluate for UTI, hematuria, glycosuria, and crystals
- Renal function tests: (BUN, creatinine levels, electrolytes): in all patients to evaluate for renal failure (obstructive nephropathy)
- Blood sugars: glucose control in patients with diabetes or if diabetic neuropathy is suspected
- Serum prostate-specific antigen levels (PSA): indicated in men with ≥ 10-year life expectancy to identify prostate cancer, if suspected
- Coagulation profile and hemoglobin levels: indicated in patients with urinary bladder tamponade
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 residual volume > 300 mL; bladder wall thickening (in chronic obstructive urinary retention)
- In both: evaluate for hydroureteronephrosis (due to bladder calculi or BPH, if present ); diagnose
- In bladder tamponade: blood clot visualized as an echogenic, mobile mass; often seen at the base of the bladder
- Transrectal ultrasound (and prostate biopsy): suspected prostate cancer
- Cystoscopy, CT urography: suspected (gross hematuria)
- Retrograde urethrogram or voiding cystourethrogram: suspected , strictures, or tumors
- Pelvic ultrasound: suspected pelvic mass
- MRI brain or spinal cord: if urinary retention is due to a neurological cause
- : preceding history of lower urinary tract symptoms
- Urodynamic studies: patients with neurogenic bladder
AUR is a 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)
- Transurethral Foley catheterization
- Suprapubic catheterization (SPC) if transurethral catheterization is not possible (e.g., urethral stricture, large prostate) or contraindicated (e.g., suspected urethral trauma, recent urethral surgery, acute bacterial prostatitis)
Treatment of the underlying cause
In all patients with acute or chronic urinary retention:
- Precipitating drugs: discontinue or substitute
- Prostatitis: antibiotics (fluoroquinolones or trimethoprim-sulfamethoxazole)
- Prostate cancer: treatment depends on the stage (see “Treatment” of )
- Bladder tamponade: clot removal and continuous bladder irrigation with sterile water/saline
- Neurogenic bladder : clean intermittent catheterization or indwelling catheter , parasympathomimetic drugs (bethanechol)
See “ Posterior urethral valves”, “Genitourinary trauma”, and “Treatment of lower urinary tract obstruction” in “ Urinary tract obstruction” for information on the management of other causative factors.