Urinary retention

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Urinary retention also known as ischuria is a lack of ability to urinate. It is a common complication of benign prostatic hypertrophy (also known as benign prostatic hyperplasia or BPH), although anticholinergics may also play a role, and requires a catheter or prostatic stent. Various medications (e.g. some antidepressants) and recreational use of amphetamines and opiates are notorious for this.

Signs and symptoms

Urinary retention is characterised by poor urinary stream with intermittent flow, straining, a sense of incomplete voiding and hesitancy (a delay between trying to urinate and the flow actually beginning). As the bladder remains full, it may lead to incontinence, nocturia (need to urinate at night) and high frequency. Acute retention caused by complete anuria is a medical emergency, as the bladder may distend (stretch) to enormous sizes and possibly tear if not dealt with quickly. If the bladder distends enough it will begin to become painful. The increase in pressure in the bladder can also prevent urine entering from the ureters or even cause urine to pass back up the ureters and get into the kidneys, causing hydronephrosis, and possibly pyonephrosis, kidney failure and sepsis. A person should go straight to an emergency department as soon as possible if unable to urinate when having a painfully full bladder.

In the longer term, obstruction of the urinary tract may cause:

• Bladder stones
• Loss of detrusor muscle tone (atonic bladder is an extreme form)
• Hydronephrosis (congestion of the kidneys)
• Hypertrophy of detrusor muscle
• Diverticula in the bladder wall (leads to stones and infection)

Causes

In the bladder

• Detrusor sphincter dyssynergia
• Neurogenic bladder (commonly pelvic splanchic nerve damage, sacral spinal cord damage, descending cortical fibers lesion, pontine micturation or storage center lesions, demyelinating diseases or Parkinson's disease)
• Iatrogenic scarring of the bladder neck (commonly from removal of indwelling catheters or cystoscopy operations)
• Damage to the bladder

In the prostate

• Benign prostatic hyperplasia
• Prostate cancer and other pelvic malignancies
• Prostatitis

Penile urethra

• Congenital urethral valves
• Phimosis or pinhole meatus
• Circumcision
• Obstruction in the urethra, for example a metastasis or a precipitated pseudogout crystal in the urine
• STD lesions (gonorrhoea causes numerous strictures, leading to a "rosary bead" appearance, whereas chlamydia usually causes a single stricture)

Other

• Paruresis ("shy bladder syndrome")- in extreme cases, urinary retention can result
• Consumption of some psychoactive substances, mainly stimulants, such as Ecstasy.
• Use of drugs with anticholinergic properties.
• Stones or metastases can theoretically appear anywhere along the urinary tract, but vary in frequency depending on anatomy

Paruresis, inability to urinate in the presence of others (such as in a public restroom), may also be classified as a type of urinary retention, although it is psychological rather than biological.

Diagnostic tests

Urine flow tests may aid in establishing the type of micturition abnormality. Common findings include a slow rate of flow, intermittent flow and a large post void residual, determined by ultrasound of the bladder. A normal test result should be 0 ml. A post void residual urine greater than 50 ml is a significant amount of urine that is associated with urinary tract infections. In adults older than 60 years, 50-100 ml of residual urine may remain after each voiding because of the decreased contractility of the detrusor muscle. In chronic retention, ultrasound of the bladder may show massive increase in bladder capacity (normal capacity being 400-600 ml).

Determination of the serum prostate-specific antigen (PSA) may aid in diagnosing or ruling out prostate cancer, though this is also raised in BPH and prostatitis. A TRUS biopsy of the prostate (trans-rectal ultra-sound guided) can distinguish between these prostate conditions. Serum urea and creatinine determinations may be necessary to rule out backflow kidney damage. Cystoscopy may be needed to explore the urinary passage and rule out blockages

Treatment

In acute urinary retention, urinary catheterization, placement of a Prostatic stent or suprapubic cystostomy instantly relieves the retention. In the longer term, treatment depends on the cause. Benign prostatic hypertrophy may respond to alpha blocker and 5-alpha-reductase inhibitor therapy, or surgically with prostatectomy or transurethral resection of the prostate (TURP).

See also

• Constipation, inability to defecate
• Urinary incontinence, inability to hold the urine

References