What are the causes of acute urinary retention?

Causes of Acute Urinary Retention

Acute urinary retention is primarily caused by obstructive, neurological, infectious/inflammatory, and iatrogenic factors, with benign prostatic hyperplasia being the most common cause in men. 1

Obstructive/Structural Causes

• Benign prostatic hyperplasia (BPH) accounts for approximately 53% of acute urinary retention cases in men, with risk increasing with age, prostate size, moderate to severe urinary symptoms, and low peak flow rates (<12 ml/sec) 1, 2, 3
• Urinary stones can cause obstruction at any level of the urinary tract 1
• Constipation with fecal impaction can lead to acute urinary retention by causing external compression of the bladder neck 1
• Phimosis in uncircumcised males can result in acute urinary retention 1
• Urethral strictures, bladder neck contractures, and other anatomical abnormalities can cause mechanical obstruction 4

Neurological Causes

• Stroke, particularly affecting the frontal lobe or pons, can cause acute urinary retention in 21-47% of patients within the first 72 hours 1
• Spinal cord injuries or compression from herniated discs, tumors, or abscesses can disrupt neural pathways controlling micturition 2
• Multiple sclerosis and other demyelinating diseases affecting sacral pathways can lead to urinary retention 4
• Diabetic neuropathy affecting bladder innervation can result in impaired bladder contractility 2

Infectious/Inflammatory Causes

• Urinary tract infections can cause acute urinary retention through inflammation and irritation of the urethral and bladder mucosa 1
• Prostatitis can cause significant prostatic swelling leading to obstruction 4
• Stevens-Johnson syndrome affecting the urogenital tract can cause acute urinary retention 1

Medication/Toxicologic Causes

• Anticholinergic medications (e.g., antihistamines, tricyclic antidepressants, antipsychotics) can impair detrusor muscle contractility 2, 4
• Alpha-adrenergic agonists can increase urethral sphincter tone 4
• Opioids can impair bladder sensation and contractility 4
• Over-the-counter cold and allergy medications with sympathomimetic effects can cause urinary retention 2

Iatrogenic/Post-Surgical Causes

• Post-surgical patients, especially those undergoing pelvic, anorectal, or urological procedures, are at high risk of acute urinary retention 1
• General anesthesia is associated with approximately half of acute retention episodes 3
• Epidural anesthesia can temporarily impair bladder sensation and function 4

Other Causes

• Immobility and prolonged bedrest can lead to acute urinary retention, particularly in hospitalized patients 1
• Psychological factors such as anxiety in unfamiliar environments (e.g., hospitals) can trigger retention 4

Risk Factors

• Advanced age significantly increases risk, with 10% of men in their 70s and 33% of men in their 80s experiencing at least one episode 5
• Male gender (due to anatomical considerations, particularly prostatic enlargement) 2
• History of previous episodes of urinary retention 2
• Moderate to severe lower urinary tract symptoms 3
• Low peak urinary flow rates (less than 12 ml/sec) 3
• Large prostate volume 3

Prevention Strategies

• Early mobilization in hospitalized patients can help prevent acute urinary retention 1
• Scheduled voiding for high-risk patients, especially post-stroke patients 1
• Finasteride treatment in men with BPH has been shown to reduce the risk of acute urinary retention by 57% when used for at least two years 3, 6
• Alpha blockers can improve voiding and reduce the risk of retention in men with BPH 7

Understanding these diverse causes is essential for proper diagnosis and management of acute urinary retention, which requires prompt bladder decompression and treatment of the underlying cause to prevent complications and improve outcomes.