Causes of Acute Urinary Retention
Acute urinary retention (AUR) is primarily caused by obstructive processes, with benign prostatic hyperplasia (BPH) accounting for approximately 53% of cases in men. 1 Understanding the various etiologies is essential for proper management and prevention of complications.
Major Categories of Causes
Obstructive/Structural Causes
- BPH - most common cause in older men, with approximately 10% of men in their 70s and 33% of men in their 80s experiencing at least one episode 2
- Urethral strictures 1
- Urinary stones - can cause obstruction at any level of the urinary tract 3, 4
- Bladder or pelvic tumors causing compression 4
- Constipation with fecal impaction 3
- Blood clots in the urinary tract 4
- Phimosis in uncircumcised males 3
Neurological Causes
- Stroke - particularly affecting the frontal lobe or pons, seen in 21-47% of patients within the first 72 hours after acute stroke 3
- Spinal cord injury or compression 4
- Multiple sclerosis 4
- Diabetic neuropathy 1
- Parkinson's disease 1
- Cauda equina syndrome - requires emergency intervention 4
Medication/Toxicologic Causes
- Anticholinergic medications (e.g., antihistamines, antidepressants) 1, 4
- Alpha-adrenergic agonists 4
- Opioid analgesics 1
- Anesthesia-induced - accounts for approximately half of acute retention episodes 5
- Alcohol intoxication 4
Infectious/Inflammatory Causes
- Urinary tract infections 3
- Prostatitis 4
- Urethritis 4
- Stevens-Johnson syndrome affecting urogenital tract 3
Other Causes
- Post-surgical (especially pelvic, anorectal, or urological procedures) 3
- Psychological factors 4
- Immobility and bedrest 3
- Pregnancy (due to compression) 4
Risk Factors
- Advanced age - strongest risk factor, especially in men 5
- Male gender 1
- Moderate to severe lower urinary tract symptoms 5
- Low peak urinary flow rates (<12 ml/sec) 5
- Large prostate volume 5
- Recent general anesthesia 5
- Prolonged bedrest or immobility 3
Clinical Presentation
- Sudden inability to void despite a full bladder 6
- Lower abdominal pain and discomfort 6
- Suprapubic distention 1
- Restlessness and agitation 4
- Overflow incontinence may be present in chronic retention 1
Diagnostic Approach
- Bladder scanning to determine post-void residual (PVR) volume - PVR >300 mL on two separate occasions persisting for at least six months defines chronic urinary retention 1
- Catheterization to measure residual volume and relieve obstruction 1
- Urinalysis to identify infection 3
- Focused neurological examination to identify potential neurological causes 1
- Ultrasound of kidneys and bladder to assess for hydronephrosis, stones, or other structural abnormalities 3
Management Considerations
- Immediate bladder decompression via catheterization is the primary initial treatment 1
- For BPH-related retention, alpha-blockers may be initiated to facilitate successful voiding trials 1
- Finasteride has been shown to reduce the risk of AUR by 57% in men with BPH when used for at least two years 5, 7
- Suprapubic catheters may improve patient comfort and decrease bacteriuria compared to urethral catheters in certain situations 1
- Indwelling catheters should be removed as soon as medically appropriate to reduce infection risk 3
- Intermittent catheterization may be necessary if post-void residual remains >100 mL 3
Complications of Untreated AUR
- Bladder overdistension injury 4
- Urinary tract infections 3
- Acute kidney injury 4
- Bladder rupture (rare but serious) 4
Prevention Strategies
- Early mobilization in hospitalized patients 3
- Avoiding medications that can precipitate urinary retention when possible 4
- Treating underlying BPH with appropriate medications 7
- Scheduled voiding for patients at risk, especially post-stroke patients 3
Understanding these causes and risk factors allows for prompt identification and management of acute urinary retention, potentially preventing serious complications and improving patient outcomes.