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Acute urinary retention is most commonly seen in older men with prostatic hypertrophy causing bladder neck obstruction (seen in 10% of men in their 70s and up to 33% of men in their 80s). The risk is increased for older men, for those with moderate to severe lower urinary tract symptoms, for those with a flow rate < 12 mL/sec, and for those with a prostate volume > 30 mL by transrectal ultrasound.
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In women, acute urinary retention is usually due to neurogenic bladder, and in younger patients, it is usually due to neurologic diseases such as multiple sclerosis or spinal cord injury. Medications that commonly induce urinary retention in susceptible patients include antihistamines, anticholinergics, antispasmodics, tricyclic antidepressants, opioids, and alpha-adrenergic agonists.