What is the appropriate management for a patient presenting with left lower quadrant abdominal rebound tenderness, suggestive of diverticulitis or appendicitis?

Management of Left Lower Quadrant Abdominal Rebound Tenderness

Obtain CT abdomen and pelvis with IV contrast immediately to confirm the diagnosis and guide treatment, as clinical examination alone is unreliable with misdiagnosis rates of 34-68%. 1, 2

Initial Diagnostic Approach

Clinical Assessment Limitations

• Do not rely on clinical examination alone to make treatment decisions—rebound tenderness in the left lower quadrant has poor diagnostic accuracy for distinguishing between diverticulitis, appendicitis, and other pathology 1
• The classic triad of left lower quadrant pain, fever, and leukocytosis is present in only 25% of diverticulitis cases 2
• 24% of appendicitis patients have no right lower quadrant pain or tenderness, and 7% of diverticulitis patients have no left lower quadrant findings 3

Mandatory Imaging

• CT abdomen and pelvis with IV contrast is rated 8/9 (usually appropriate) and has 98-100% diagnostic accuracy 2
• CT changes management in 37% of patients and reduces hospital admissions by >50% 2
• CT identifies complications (abscess, perforation, fistula) and alternative diagnoses that alter treatment 1, 2

Laboratory Markers to Obtain

• White blood cell count with differential (left shift >75% suggests bacterial infection) 1
• C-reactive protein (CRP >170 mg/L predicts severe diverticulitis with 87.5% sensitivity and 91.1% specificity) 1
• Procalcitonin 1

Treatment Algorithm Based on CT Findings

Uncomplicated Diverticulitis (No abscess, perforation, or distant free air)

For immunocompetent patients: Conservative management WITHOUT antibiotics 1, 2

• Clear liquid diet with advancement as tolerated 2
• Oral analgesics for pain control 2
• Outpatient management if able to tolerate oral intake 2

For immunocompromised or elderly patients: Antibiotics for maximum 7 days 1, 2

• Ertapenem 1 g IV/IM every 24 hours, OR 1
• Eravacycline 1 mg/kg IV every 12 hours 1

Complicated Diverticulitis with Small Abscess (<4 cm)

Antibiotics alone for 7 days without drainage 1, 2

• Same antibiotic regimens as above 1

Complicated Diverticulitis with Large Abscess (≥4 cm)

Percutaneous drainage PLUS antibiotics for 4 days 1, 2

• Stop antibiotics at 4 days if source control is adequate in immunocompetent, non-critically ill patients 1, 2
• Continue up to 7 days in immunocompromised or critically ill patients based on clinical response and inflammatory markers 1, 2

If percutaneous drainage not feasible:

• Immunocompetent, non-critically ill: Consider antibiotics alone as primary treatment 1
• Critically ill or immunocompromised: Surgical intervention 1

Septic Shock (Any stage)

Escalate to broad-spectrum carbapenem therapy immediately 1

• Meropenem 1 g IV every 6 hours by extended infusion or continuous infusion, OR 1
• Doripenem 500 mg IV every 8 hours by extended infusion, OR 1
• Imipenem/cilastatin 500 mg IV every 6 hours by extended infusion 1

Perforation with Diffuse Peritonitis

Emergency surgical consultation for:

• Primary resection and anastomosis with or without diverting stoma (clinically stable patients without major comorbidities) 1
• Hartmann's procedure (critically ill patients or those with multiple major comorbidities) 1

Critical Pitfalls to Avoid

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 continuing antibiotics 1, 2

Diagnostic Pitfalls

• CT findings suggesting cancer rather than diverticulitis include pericolonic lymphadenopathy >1 cm with or without pericolonic edema—these patients need colonoscopy 2
• Do not perform routine colonoscopy after CT-confirmed diverticulitis except for age-appropriate screening, unless abscess, perforation, or fistula is present 2

Alternative Diagnoses to Consider

• Primary epiploic appendagitis presents with focal left lower quadrant tenderness but typically lacks fever, rebound tenderness, and leukocytosis (present in only 7.1%, 14.3%, and 15.4% respectively vs. 40%, 52%, and 52% in diverticulitis) 4
• CT shows oval fatty mass with hyperattenuated ring sign without bowel wall thickening in epiploic appendagitis 4, 5
• Atypical appendicitis can present with left-sided pain due to malrotation 2

Red Flags Requiring Emergency Surgery

Immediate surgical consultation if any of the following are present:

• Diffuse peritonitis with guarding 2
• Signs of shock (hypotension, tachycardia, altered mental status) 2
• Free air on CT indicating perforation 1
• Inability to pass gas or stool with complete obstruction 2
• Fecal peritonitis 1