What are the causes of urinary retention (inability to empty the bladder)?

From the Guidelines

Urinary retention requires immediate medical attention, and the most appropriate initial treatment is catheterization to relieve discomfort, as indicated by the most recent guidelines 1. The condition can occur acutely or chronically and is caused by either obstruction, such as an enlarged prostate or urethral stricture, or detrusor muscle dysfunction due to neurological conditions or medications. Some key points to consider in the management of urinary retention include:

• Catheterization is recommended for acute urinary retention, with a post-void residual bladder volume > 500 cm3, as detected by a bladder scanner 1.
• For benign prostatic hyperplasia (BPH), alpha-blockers like tamsulosin or 5-alpha-reductase inhibitors such as finasteride may be prescribed 1.
• Anticholinergic medications should be discontinued if they're contributing to the problem.
• For neurogenic causes, clean intermittent catheterization may be necessary 1.
• Surgical interventions like transurethral resection of the prostate (TURP) might be required for severe cases of BPH. The diagnosis of urethral stricture, a potential cause of urinary retention, should include urethro-cystoscopy, retrograde urethrography (RUG), voiding cystourethrography (VCUG), or ultrasound urethrography 1. Complications of untreated urinary retention include urinary tract infections, bladder damage, and kidney problems, emphasizing the need for prompt medical care. Patients should seek immediate medical care for sudden inability to urinate, severe lower abdominal pain with a full bladder, or if they pass only small amounts of urine despite feeling the need to urinate more.

From the FDA Drug Label

The improvement in BPH symptoms was seen during the first year and maintained throughout an additional 5 years of open extension studies. Effect on Acute Urinary Retention and the Need for Surgery In A Long-Term Efficacy and Safety Study, efficacy was also assessed by evaluating treatment failures Treatment failure was prospectively defined as BPH-related urological events or clinical deterioration, lack of improvement and/or the need for alternative therapy. BPH-related urological events were defined as urological surgical intervention and acute urinary retention requiring catheterization. The following table (Table 5) summarizes the results. Patients (%)* Event Placebo N=1503 Finasteride N=1513 Relative Risk† 95% CI P Value† Table 5: All Treatment Failures in A Long-Term Efficacy and Safety Study All Treatment Failures 37.1 26.2 0.68 (0.57 to 0.79) <0.001 Surgical Interventions for BPH 10.1 4.6 0.45 (0.32 to 0.63) <0.001 Acute Urinary Retention Requiring Catheterization 6.6 2.8 0. 43 (0.28 to 0.66) < 0.001 Compared with placebo, finasteride tablets was associated with a significantly lower risk for acute urinary retention or the need for BPH-related surgery [13.2% for placebo vs 6. 6% for finasteride tablets; 51% reduction in risk, 95% CI: (34 to 63%)]. Compared with placebo, finasteride tablets was associated with a significantly lower risk for surgery [10.1% for placebo vs 4.6% for finasteride tablets; 55% reduction in risk, 95% CI: (37 to 68%)] and with a significantly lower risk of acute urinary retention [6.6% for placebo vs 2. 8% for finasteride tablets; 57% reduction in risk, 95% CI: (34 to 72%)]

• Finasteride reduces the risk of acute urinary retention by 57% compared to placebo, with a 95% CI of (34 to 72%) 2.
• The study shows that finasteride is effective in reducing the risk of acute urinary retention requiring catheterization, with a relative risk of 0.43 (0.28 to 0.66) compared to placebo 2.

From the Research

Definition and Causes of Urinary Retention

• Urinary retention is the acute or chronic inability to voluntarily pass an adequate amount of urine, predominantly affecting men 3
• The most common causes are obstructive in nature, with benign prostatic hyperplasia (BPH) accounting for 53% of cases 3
• Other causes include infectious, inflammatory, iatrogenic, and neurologic factors 3

Evaluation and Initial Management

• Initial evaluation should involve a detailed history and focused physical examination with neurologic evaluation 3
• Diagnostic testing should include measurement of postvoid residual (PVR) volume of urine 3
• Initial management involves assessment of urethral patency with prompt and complete bladder decompression by catheterization 3
• Suprapubic catheters may improve patient comfort and decrease bacteriuria and the need for recatheterization 3

Treatment Options

• Alpha blockers, such as alfuzosin, tamsulosin, and silodosin, may increase the success rate of trial without catheter (TWOC) 4, 5
• Alpha blockers relax prostatic smooth muscle cells, decreasing resistance to urinary flow and improving urinary symptoms 4
• Combination therapy with alpha blockers, such as alfuzosin plus tamsulosin, may be more effective than monotherapy 5
• Medical therapy, including androgen-suppressing therapy and alpha-adrenoceptor blockade, may be effective in treating BPH 6

Specific Alpha Blockers and Their Effects

• Alfuzosin, tamsulosin, and silodosin have been shown to be effective in increasing TWOC success rates 4, 5
• Doxazosin did not show a significant difference in TWOC success rate compared to placebo 5
• Tamsulosin lacks significant effects on blood pressure, making it a suitable option for patients with BPH 6