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

Acute Bacterial Prostatitis

The most likely diagnosis is A. Prostatitis (acute bacterial prostatitis). The acute 12-hour onset of painful urination, perianal pain, and urinary retention combined with a small, tender prostate on digital rectal examination is pathognomonic for acute bacterial prostatitis 1, 2, 3.

Why Prostatitis is the Clear Answer

The clinical presentation definitively points to acute bacterial prostatitis based on three key distinguishing features:

• Acute onset (12 hours) rules out chronic conditions like BPH, which develops gradually over months to years 1
• Small, tender prostate on DRE is the hallmark physical examination finding that distinguishes prostatitis from BPH 1, 2, 3
• Perianal pain is a characteristic symptom of acute prostatitis that is absent in other differential diagnoses 2, 3

The combination of dysuria, urinary retention, and a tender prostate gland represents the classic triad of acute bacterial prostatitis 3. This condition causes pelvic pain and urinary tract symptoms including dysuria, urinary frequency, and urinary retention 2, 3.

Why the Other Options Are Incorrect

BPH (Option D) is Excluded by Multiple Findings:

• BPH typically presents with an enlarged prostate on DRE, not a small one 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 1
• BPH does not cause perianal pain 1

Neurogenic Bladder (Option B) is Ruled Out:

• 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 less likely 1
• No mention of neurologic symptoms or risk factors (spinal cord injury, diabetes with neuropathy, multiple sclerosis) in this patient 1

UTI (Option C) is Less Likely:

• While UTI can cause dysuria, it does not typically cause perianal pain 2
• UTI alone does not produce a tender prostate on examination 3
• The constellation of findings—particularly the tender prostate and perianal pain—indicates prostate involvement, making this acute bacterial prostatitis rather than simple cystitis 2, 3

Clinical Pitfall: Depression Medication Connection

Important consideration: The patient is on depression medication, which may include anticholinergic agents that can contribute to urinary retention 1. However, this would not explain the tender prostate or perianal pain, which are specific to acute prostatitis 3. The medication may have exacerbated the retention but is not the primary cause 2.

Immediate Management Approach

This patient requires urgent treatment with broad-spectrum antibiotics:

• First-line therapy includes intravenous piperacillin-tazobactam, ceftriaxone, or oral ciprofloxacin for 2-4 weeks, with a 92-97% success rate 2
• Obtain urine cultures to determine the responsible bacteria (80-97% are gram-negative organisms like E. coli, Klebsiella, or Pseudomonas) 2, 3
• Consider hospitalization if the patient is systemically ill, unable to voluntarily urinate (as in this case), unable to tolerate oral intake, or has risk factors for antibiotic resistance 3
• Immediate urinary catheterization is needed for the 12-hour urinary retention 3