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

Acute Bacterial Prostatitis

The most likely underlying cause is acute bacterial prostatitis (Option A). The combination of acute onset urinary retention (12 hours), painful micturition, perianal pain, and a small tender prostate on DRE is pathognomonic for acute bacterial prostatitis. 1, 2, 3

Why Prostatitis is the Correct Answer

The clinical presentation is diagnostic for acute bacterial prostatitis based on three key features:

• Acute onset (12 hours) - This timeframe rules out chronic conditions like BPH, which develops gradually over months to years, not acutely. 1

• Small, tender prostate on DRE - This is the hallmark physical examination finding that distinguishes prostatitis from BPH. A tender prostate is characteristic of acute infection/inflammation of the gland. 1, 2, 3

• Classic symptom triad - Dysuria, perianal/pelvic pain, and urinary retention together strongly suggest acute bacterial prostatitis. 2, 3, 4

Why the Other Options Are Incorrect

BPH (Option D) is Excluded Because:

• BPH presents with an enlarged prostate on DRE, not a small one as described in this case. 1

• BPH causes gradual onset of obstructive symptoms over months to years, not acute 12-hour retention. 1

• The prostate in BPH is typically non-tender on examination, unlike the tender prostate in this patient. 1

Neurogenic Bladder (Option B) is Excluded Because:

• Neurogenic bladder requires underlying neurologic disease and would show abnormal neurologic examination findings, particularly lower extremity neuromuscular dysfunction and abnormal anal sphincter tone. 1

• The absence of tender prostate or perianal pain makes neurogenic bladder unlikely. 1

• There is no mention of neurologic disease, prior spinal trauma, or neurologic deficits in this patient. 1

UTI (Option C) is Less Likely Because:

• While UTI can cause dysuria, it does not typically cause acute urinary retention or perianal pain. 2

• Simple UTI would not produce a tender prostate on DRE - this finding specifically indicates prostatic involvement. 5, 3

• The clinical picture describes prostatitis (a specific type of UTI involving the prostate), not simple cystitis. 2, 4

Clinical Pitfall: Depression Medication

The patient's depression medication is likely contributing to urinary retention. Anticholinergic antidepressants (tricyclics) and some SSRIs can cause urinary retention, which may have been exacerbated by the acute prostatic inflammation and edema. 2 However, the medication alone does not explain the tender prostate and perianal pain.

Immediate Management Approach

This patient requires urgent treatment with broad-spectrum antibiotics:

• First-line therapy includes intravenous or oral fluoroquinolones (ciprofloxacin), ceftriaxone, or piperacillin-tazobactam for 2-4 weeks, with 92-97% success rates. 2, 3

• Urethral catheterization is mandatory to relieve the acute retention and prevent urethral stricture formation. 3

• Obtain urine cultures before starting antibiotics to identify the causative organism (80-97% are gram-negative bacteria like E. coli). 2, 3

• Consider hospitalization if the patient appears systemically ill, has fever/chills, cannot tolerate oral intake, or has risk factors for antibiotic resistance. 3