What is the initial approach to managing left lower quadrant pain in an adult male without dysuria or constipation?

Initial Management of Left Lower Quadrant Pain in Adult Males Without Dysuria or Constipation

Order CT abdomen and pelvis with IV contrast immediately—this is the single most important diagnostic test with 98% accuracy and should be performed before any other imaging or empiric treatment. 1, 2

Diagnostic Approach

Immediate CT Imaging is Essential

• CT with IV contrast is rated 8/9 (usually appropriate) by the American College of Radiology and should be the first-line imaging modality for left lower quadrant pain in adult males 1
• This single test identifies acute diverticulitis (the most common cause), detects life-threatening complications (perforation, abscess), and reveals alternative diagnoses that clinically mimic diverticulitis 1, 2
• CT changes management in 42% of patients and alters the leading diagnosis in 49% of cases 1
• Do not rely on clinical diagnosis alone—misdiagnosis rates range from 34-68% without imaging 2

Critical CT Findings to Identify

When reviewing the CT scan, specifically look for:

• Pericolonic lymphadenopathy >1 cm in short axis—this strongly suggests perforated colon cancer rather than diverticulitis and mandates colonoscopy 1, 2, 3
• Extraluminal air—indicates perforation requiring urgent surgical consultation 1, 2
• Abscess size—measure carefully as <4 cm receives antibiotics alone while ≥4 cm requires percutaneous drainage 2
• Bowel wall thickening with pericolonic fat stranding—classic for diverticulitis 2

Clinical Red Flags Requiring Emergency Evaluation

Before ordering imaging, assess for these features that indicate complicated disease:

• Fever combined with inability to pass gas or stool 2
• Severe abdominal tenderness with guarding or rebound 2
• Signs of shock (hypotension, tachycardia, altered mental status) 2
• Vomiting or bloody stools 2
• Progressively worsening pain over several days 2

Any of these findings mandate immediate surgical consultation regardless of imaging results. 2

Management Based on CT Results

Uncomplicated Diverticulitis (No Abscess, No Perforation)

• Conservative management without antibiotics is appropriate for immunocompetent patients 2
• Advance from clear liquids as tolerated with oral analgesics for pain control 2
• Reserve antibiotics (Ertapenem 1g q24h or Eravacycline 1mg/kg q12h) for immunocompromised or elderly patients only, limited to maximum 7 days 2

Complicated Diverticulitis with Small Abscess (<4 cm)

• Antibiotic therapy alone for 7 days without drainage 2
• Use Ertapenem 1g q24h or Eravacycline 1mg/kg q12h 2

Complicated Diverticulitis with Large Abscess (≥4 cm)

• Percutaneous drainage combined with antibiotics for 4 days 2
• Stop antibiotics at 4 days if source control is adequate in immunocompetent, non-critically ill patients 2

Perforation with Peritonitis or Free Air

• Emergent surgical consultation for operative management 2
• If septic shock is present, use Meropenem 1g q6h by extended infusion, Doripenem 500mg q8h by extended infusion, or Imipenem/cilastatin 500mg q6h by extended infusion 2

Critical Pitfalls to Avoid

Missing Colon Cancer

• Perforated adenocarcinoma can perfectly mimic diverticulitis both clinically and radiographically 1, 3
• The key distinguishing feature is pericolonic lymphadenopathy >1 cm—when present, this strongly suggests malignancy over diverticulitis 1, 2, 3
• Routine colonoscopy after CT-confirmed diverticulitis is NOT warranted except for age-appropriate screening, unless abscess, perforation, or fistula is identified 1, 2

Rare but Important Alternative Diagnoses

While diverticulitis accounts for 70% of left lower quadrant pain in older adults 1, CT will identify these mimics:

• Left-sided appendicitis (from midgut malrotation, situs inversus, or redundant cecum)—presents identically to diverticulitis but requires surgical management 4, 5, 6, 7
• Epiploic appendagitis—benign self-limited condition requiring no antibiotics 1
• Colitis, inflammatory bowel disease, bowel obstruction, or hernia 1

Antibiotic Duration Errors

• Never continue antibiotics beyond 7 days in uncomplicated cases—this increases resistance without improving outcomes 2
• If signs of infection persist beyond 7 days, obtain repeat imaging to assess for inadequate source control rather than extending antibiotics 2

Alternative Imaging Considerations

• Ultrasound with graded compression can be used but is operator-dependent and limited in obese patients—it should not replace CT when CT is available 1
• CT without IV contrast (rated 6/9) is acceptable only when IV contrast is contraindicated, though less accurate for detecting abscesses 1, 2
• MRI is not useful for initial evaluation—it is less sensitive for extraluminal air and urinary calculi, more time-consuming, and more subject to motion artifact 1
• Plain radiography has no role unless free perforation (pneumoperitoneum) or obstruction is suspected 1