What is the most likely underlying cause of a middle-aged male's symptoms of painful urination (dysuria), perianal pain, and urinary retention, with a digital rectal exam (DRE) showing a palpable, small, tender prostate, while on depression medication?

Acute Bacterial Prostatitis

The most likely underlying cause is A. Prostatitis (acute bacterial prostatitis). This middle-aged male presents with the classic triad of acute bacterial prostatitis: painful micturition (dysuria), perianal pain, and acute urinary retention, combined with a small, tender prostate on digital rectal examination 1, 2.

Clinical Reasoning

The clinical presentation strongly points to acute bacterial prostatitis based on several key features:

• Acute urinary retention (12 hours) combined with dysuria and perianal/pelvic pain is pathognomonic for acute bacterial prostatitis 1, 2
• Small, tender prostate on DRE is the hallmark physical examination finding that distinguishes prostatitis from BPH 2
• Acute onset (12 hours) rules out chronic conditions like BPH, which develops gradually over months to years 3

Why Other Diagnoses Are Less Likely

BPH (Option D) - Excluded

• BPH typically presents with an enlarged prostate on DRE, not a small one 3
• BPH causes gradual onset of obstructive symptoms over months to years, not acute 12-hour retention 3
• BPH prostate is typically non-tender on examination 3

Neurogenic Bladder (Option B) - Excluded

• Requires underlying neurologic disease (spinal cord injury, multiple sclerosis, diabetes with neuropathy) 3
• Would show abnormal neurologic examination findings, particularly lower extremity neuromuscular dysfunction and abnormal anal sphincter tone 3
• Does not typically cause a tender prostate or perianal pain 3
• Depression medication alone (likely SSRIs) can cause urinary retention but would not explain the tender prostate or perianal pain

UTI (Option C) - Less Likely as Primary Diagnosis

• Simple UTI (cystitis) does not cause prostate tenderness on DRE 2
• UTI alone does not typically cause acute urinary retention in middle-aged men without underlying prostatic pathology 4
• The tender prostate indicates prostatic involvement, making this acute bacterial prostatitis rather than simple cystitis 1, 2

Diagnostic Confirmation

The diagnosis should be confirmed with:

• Urinalysis and urine culture to identify the causative organism (80-97% are gram-negative bacteria like E. coli, Klebsiella, or Pseudomonas) 1, 2
• Avoid vigorous prostatic massage during DRE as this can precipitate bacteremia in acute bacterial prostatitis 2
• Consider post-void residual measurement after catheterization if urinary retention persists 2

Immediate Management

Broad-spectrum antibiotics should be initiated immediately after obtaining urine culture:

• First-line therapy: Intravenous piperacillin-tazobactam, ceftriaxone, or oral ciprofloxacin for 2-4 weeks (92-97% success rate) 1, 2
• Urinary catheterization is required for the acute retention 2
• Hospitalization should be considered given the systemic symptoms and urinary retention 2

Critical Pitfall

Do not confuse acute bacterial prostatitis with BPH - the key distinguishing features are the acute onset, tender prostate, and small (not enlarged) prostate size on examination 1, 2. Missing this diagnosis can lead to progression to prostatic abscess requiring surgical intervention 5.