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Acute urinary retention is a common painful urologic emergency characterized by a sudden inability to pass urine, and is associated with lower abdominal distention or pain. Most patients with urinary retention are elderly men, and the incidence and risk increase with age. The most common cause of urinary retention is benign prostatic hyperplasia (BPH), with or without precipitating factors, inducing urinary bladder outlet obstruction.1 A comprehensive history and physical examination are needed to identify the underlying disease process and the factors triggering obstruction. The current management of urinary retention involves the placement of a catheter (urethral or suprapubic), supportive medical therapy, and disposition decision making.

The reported incidence of acute urinary retention in large population-based studies varies from 2.2 to 6.8 per 1000 men per year2–5 with a 4% to 73% 10-year cumulative risk.6,7 It is estimated that 1 in 10 men in their 70s will experience urinary retention within the next 5 years. The risk for men in their 80s is nearly 1 in 3.2 The risk factors for urinary retention in men are related to age, symptom severity, prostate volume (size), and urinary flow rate.2 There is a 20% recurrence rate within 6 months after an episode of urinary retention.5 The recently available data on the incidence of urinary retention based on different descriptive studies, including population-based, observational, and placebo-control group of BPH studies, varied from 1.9% to 39.0% overall, 0.37% to 13.0% per year, and 3.7 to 130.0 per 1000 patient-years.8 This risk is cumulative and increases with advancing age. Due to a very low occurrence rate in females, few scientific data documenting the incidence of urinary retention in woman are available.

In certain patient groups, the onset of urinary retention predicts significant future mortality.9 In men with spontaneous urinary retention, the mortality rate at 1 year increases from 4.1% in patients aged 45 to 54 years to 32.8% in those aged 85 years and older. Men with spontaneous urinary retention and comorbidity who are admitted to hospital have a higher mortality at both 90 days and at 1 year than those without comorbidity in the corresponding age groups. Approximately half of the men aged 85 years and older with at least one comorbid condition died within the first year after acute urinary retention.9

Urinary retention results from increased resistance to urine flow by mechanical or dynamic means, diminished neurogenic control of detrusor muscle contractility, and subsequent decompensation of voiding function. The voiding process, or micturition, involves the complex integration and coordination of high cortical neurologic (sympathetic, parasympathetic, and somatic) and muscular (detrusor and sphincter smooth muscle) functions. Normal bladder voiding requires coordinated contraction of the bladder smooth musculature, concomitant lowering of resistance at the level of the smooth and striated sphincter muscle, and absence of anatomic obstruction. Therefore, neurologic modulation plays a major role in the voiding process.

Sympathetic innervation, responsible for ...

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