This randomized controlled trial will compare three medication strategies before trial without catheter in men with acute urinary retention due to benign prostatic hyperplasia who were already taking tamsulosin 0.4 mg once daily before the retention episode. After urethral catheterization, eligible participants will be randomly assigned to one of three groups for 7 days: continuation of tamsulosin 0.4 mg once daily, escalation to tamsulosin 0.8 mg once daily, or switching to silodosin 8 mg once daily. The urethral catheter will be removed on Day 7, and the ability to void successfully without re-catheterization will be assessed. Follow-up will continue to Day 30, with additional recording of catheter-free status, recurrent urinary retention, urinary flow, post-void residual urine, symptom scores, adverse drug events, catheter-related complications, and the need for later benign prostatic hyperplasia-related surgery.

Acute urinary retention is a common emergency complication of benign prostatic hyperplasia. Standard management includes immediate bladder decompression by urethral catheterization followed by alpha-blocker therapy before attempting catheter removal. However, the optimal management strategy is unclear in men who develop acute urinary retention despite already receiving standard-dose tamsulosin 0.4 mg once daily.

This trial is designed to evaluate whether continuing tamsulosin 0.4 mg, increasing the dose to tamsulosin 0.8 mg, or switching to silodosin 8 mg provides better clinical outcomes before trial without catheter. Eligible men aged 50 years or older with painful acute urinary retention presumed to be secondary to benign prostatic enlargement or obstruction, and who were already taking tamsulosin 0.4 mg once daily for at least 4 weeks before the retention episode, will be enrolled after successful urethral catheterization and written informed consent.

Participants will be randomized in a 1:1:1 ratio to one of three parallel treatment arms. The assigned medication will be given for 7 days while the urethral catheter remains in place. On Day 7, the catheter will be removed in the outpatient urology clinic. Trial without catheter success will be assessed using a predefined clinical definition based on spontaneous voiding, voided volume, post-void residual urine measured by ultrasound, absence of clinically significant voiding difficulty, and no need for re-catheterization within 24 hours.

Participants will be followed until Day 30 for urinary outcomes and safety assessment. The study will also record adverse drug events and catheter-related complications. Participants who fail the Day-7 trial without catheter will be managed according to standard clinical care, including re-catheterization and possible rescue trial without catheter or further benign prostatic hyperplasia management according to clinical judgment.

Inclusion Criteria:

• Male patients aged 50 years or older.
• Acute urinary retention requiring urethral catheterization.
• Presumed acute urinary retention secondary to benign prostatic enlargement or benign prostatic obstruction.
• Already receiving tamsulosin 0.4 mg once daily for at least 4 weeks before the acute urinary retention episode.
• Successful urethral catheterization at presentation.
• Initial catheterized urine volume ≤1000 mL, with a clinical presentation consistent with painful acute urinary retention.
• Prostate enlargement on ultrasound or clinical assessment consistent with benign prostatic hyperplasia or benign prostatic obstruction.
• Ability to provide written informed consent.

Exclusion Criteria:

• Known or suspected prostate cancer.
• Previous prostate surgery.
• Previous urethral stricture disease or urethral surgery.
• Neurogenic bladder or known neurological disease affecting voiding.
• Chronic urinary retention rather than acute painful retention.
• Acute urinary retention due to non-BPH causes, including clot retention, bladder stone obstruction, acute prostatitis, urethral trauma, or drug-induced retention.
• Severe urinary tract infection, sepsis, or fever at presentation.
• Gross hematuria requiring irrigation.
• Failed urethral catheterization or need for suprapubic catheterization.
• Current use of silodosin, alfuzosin, doxazosin, terazosin, tadalafil, anticholinergics, beta-3 agonists, or other drugs that may significantly affect voiding.
• Severe renal impairment requiring urgent intervention.
• Symptomatic postural hypotension or recurrent syncope.
• Known hypersensitivity to silodosin.
• Severe hepatic impairment.
• Inability to comply with follow-up.

Individual participant data will not be shared because the study includes individual-level clinical data related to acute urinary retention, medication exposure, catheterization, follow-up outcomes, and adverse events. Only aggregated, de-identified results will be reported in publications or presentations. Any future sharing of de-identified participant-level data would require additional approval from the Research Ethics Committee, Faculty of Medicine, Beni-Suef University.

The outcomes assessor evaluating Trial Without Catheter outcome, post-void residual urine by ultrasound, and uroflowmetry will be blinded to treatment allocation.