Urinary Retention
Urinary retention is failure to empty the bladder: acute retention is usually painful and needs prompt drainage, while chronic retention may be painless but can cause overflow, hydronephrosis and acute kidney injury, so the cause, residual volume and upper-tract risk determine urgency.
Definition
Urinary retention is failure to empty the bladder voluntarily and completely. Acute retention is sudden, usually painful inability to pass urine. Chronic retention is gradual incomplete emptying with a persistently raised residual, which may be painless and complicated by overflow incontinence, hydronephrosis or renal impairment.
First principles
Voiding requires both an open outlet and an active detrusor
Retention results from outlet obstruction, impaired detrusor contraction or both. Prostatic obstruction, urethral stricture, clot, stone, constipation, pelvic disease and postoperative swelling can block flow; medicines, over-distension and neurological disease can weaken detrusor or sphincter coordination.
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