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 an 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

• Enlarged prostate gland
  • Benign prostatic hyperplasia (most common)
  • Prostate cancer
  • Acute prostatitis (rare) ^[1]
• Urethral narrowing
  • Urethral stricture (see “Subtypes and variants” below.)
  • Urethral carcinoma
  • Posterior urethral valves
  • Urethritis (inflamed, edematous urethra)
  • Meatal stenosis (rare) ^[2]
  • Phimosis and paraphimosis
• Bladder neck obstruction
  • Bladder calculi
  • Bladder cancer
  • Urinary bladder tamponade ^[3][4]
• Extrinsic obstruction (rare)
  • Anterior vaginal wall prolapse
  • Pelvic masses (e.g., benign/malignant ovarian tumor)
  • Rectal mass or fecal impaction
• Urethral/bladder trauma (e.g., urethral transection)

Functional obstruction

• Detrusor underactivity and/or sphincter overactivity
  • Neurological causes (neurogenic bladder)
    • Central nervous system
      • Spinal cord compression (e.g., intervertebral disc protrusion/herniation, tumors, epidural abscess/hematoma) or trauma
      • Congenital anomalies of the spinal cord (e.g., meningomyelocele, spina bifida)
      • Stroke
      • Multiple sclerosis, Parkinson disease
    • Peripheral nervous system
      • Damage to pelvic splanchnic nerves (bladder denervation) → causes ↓ bladder sensation and detrusor contractility → infrequent, incomplete urination → overflow incontinence
        • Diabetic autonomic neuropathy ^[5]
        • Trauma (e.g., pelvic fracture, surgery/radiation of the pelvis)
  • Drug-induced urinary retention ^[6]
    • Due to detrusor underactivity: anticholinergics, first-generation antihistamines, tricyclic antidepressants, antipsychotics, calcium channel blockers, antiparkinson agents
    • Due to increased urethral sphincter tone; : sympathomimetics, nonselective beta blockers, opioids)
• Detrusor-sphincter dyssynergia
• Bladder neck dysfunction
• Postoperative urinary retention

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 features ^[11]
  • May be asymptomatic until manifesting with acute urinary retention
  • Symptoms of bladder outlet obstruction
    • Feeling of incomplete bladder emptying
    • Weak stream
    • Straining to urinate
  • Genitourinary pain
  • Urinary tract infections
  • Ejaculatory dysfunction
• Diagnostics
  • Uroflowmetry: plateau-shaped uroflow curve
  • Retrograde urethrography/voiding cystourethrography: visualizes urethral strictures
• Treatment
  • 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. ^[1]

Laboratory studies

• 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 to identify prostate cancer, if suspected ^[12]
• Coagulation profile and hemoglobin levels: indicated in patients with urinary bladder tamponade

Imaging

• Ultrasound of the kidney, ureter, and bladder: indicated in all patients with urinary retention
  • AUR: bladder distended with > 400 mL of urine ^[13][14]
  • CUR: post-void residual volume > 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

Further investigations

• Transrectal ultrasound (and prostate biopsy): suspected prostate cancer
• Cystoscopy, CT urography: suspected bladder cancer (gross hematuria)
• Retrograde urethrogram or voiding cystourethrogram: suspected urethral trauma, strictures, or tumors
• Pelvic ultrasound: suspected pelvic mass
• MRI brain or spinal cord: if urinary retention is due to a neurological cause
• Uroflowmetry: preceding history of lower urinary tract symptoms ^[15][16]
• 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 ^[10][17]

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 ^{[10][17][18][19]}

In all patients with acute or chronic urinary retention:

• Precipitating drugs: discontinue or substitute
• Benign prostatic hyperplasia
  • Alpha blockers (e.g., tamsulosin, alfuzosin) and trial void without catheter
  • TURP
• Prostatitis: antibiotics (fluoroquinolones or trimethoprim-sulfamethoxazole)
• Prostate cancer: treatment depends on the stage (see “Treatment” of prostate cancer)
• Bladder tamponade
  • Removal of the obstructing blood clot
  • Continuous bladder irrigation with sterile water/saline ^[3]
• 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.

Complications of urinary retention

• Acute urinary retention: renal failure (acute kidney injury or obstructive nephropathy)
• Chronic urinary retention
  • UTI
  • Vesicoureteric reflux → hydronephrosis → renal failure
  • Urolithiasis
  • Overflow incontinence

Complications of bladder decompression ^[20]

Complications of bladder decompression via catheterization are rare and usually self-limiting.

• Hematuria
• Transient hypotension
• Postobstructive diuresis

We list the most important complications. The selection is not exhaustive.

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5. Urinary bladder tamponade (blood clots in the bladder). http://www.ebm-guidelines.com/go/ebm/ebm00239.html. Updated: March 21, 2016. Accessed: March 14, 2017.
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