What are the appropriate diagnostic and treatment approaches for left-sided abdominal pain?

Diagnostic and Management Approach for Left-Sided Abdominal Pain

Initial Diagnostic Strategy

When diagnostic uncertainty exists after history and physical examination, obtain CT abdomen and pelvis with IV contrast to establish the diagnosis. 1

Key Clinical Features to Assess

• Left lower quadrant tenderness, CRP >50 mg/L, and absence of vomiting together predict diverticulitis with 97% accuracy, though this triad occurs in only 24% of patients. 2
• Clinical diagnosis alone has misdiagnosis rates of 34-68%, making imaging essential when uncertainty persists. 2
• The classic triad of left lower quadrant pain, fever, and leukocytosis appears in only 25% of diverticulitis cases. 2

Imaging Recommendations

• CT abdomen and pelvis with IV contrast is the preferred imaging modality, with 94% sensitivity and 99% specificity for acute left-sided colonic diverticulitis. 1
• CT provides diagnostic accuracy of 98% and changes management decisions in 25% of patients with abdominal pain. 2, 3
• For premenopausal women with suspected gynecologic pathology, obtain pelvic/transvaginal ultrasound as the initial study. 2
• CT without IV contrast is acceptable when contrast is contraindicated but has reduced accuracy for detecting abscesses. 2

Management Based on CT Findings

Uncomplicated Diverticulitis (Localized Inflammation Only)

For select immunocompetent patients with uncomplicated left-sided colonic diverticulitis, manage initially without antibiotics using observation with supportive care (bowel rest and hydration). 1

Criteria for Outpatient Management Without Antibiotics

• Manage select patients with acute uncomplicated diverticulitis in the outpatient setting rather than hospitalization. 1
• "Select" patients must meet all criteria: immunocompetent, no systemic inflammatory response, not medically frail, able to tolerate oral intake, and have adequate social/family support for monitoring. 1
• This approach shows no differences in complications (abscess, fistula, stenosis, obstruction), quality of life, need for surgery, or long-term recurrence compared to antibiotic treatment. 1

When Antibiotics Are Indicated for Uncomplicated Disease

• Use antibiotics only in immunocompromised or elderly patients with uncomplicated diverticulitis, limited to maximum 7 days. 2, 4
• Recommended regimens: Ertapenem 1 g every 24 hours OR Eravacycline 1 mg/kg every 12 hours. 2

Complicated Diverticulitis (Abscess, Perforation, Fistula, Obstruction)

Small Abscess (<3-4 cm)

• Treat with antibiotic therapy alone for 7 days without percutaneous drainage. 2, 4
• Use same antibiotic regimens as uncomplicated disease. 2

Large Abscess (≥3-4 cm)

• Perform percutaneous drainage combined with antibiotics for 4 days in immunocompetent, non-critically ill patients. 2, 4
• Stop antibiotics at 4 days if source control is adequate. 4
• Continue antibiotics up to 7 days in immunocompromised or critically ill patients, guided by clinical response. 4

Septic Shock

• Use Meropenem 1 g every 6 hours by extended infusion, Doripenem 500 mg every 8 hours by extended infusion, OR Imipenem/cilastatin 500 mg every 6 hours by extended infusion. 2

Red Flag Symptoms Requiring Emergency Evaluation

Immediately refer to the emergency department for any of the following: 2

• Fever with inability to pass gas or stool (present in 90% of large bowel obstructions) 2
• Severe abdominal tenderness with guarding or rebound (peritonitis signs) 2
• Vomiting, bloody stools, or signs of shock 2
• Progressively worsening pain over several days 2
• Complete absence of bowel movements with abdominal distension 2

High-Risk Features for Progression to Complicated Disease

• Symptoms lasting longer than 5 days 1
• Vomiting 1
• Systemic comorbidity 1
• C-reactive protein >140 mg/L 1
• CT findings of pericolic extraluminal air, fluid collection, or longer inflamed colon segment 1

Critical Pitfalls to Avoid

• Pericolonic lymphadenopathy >1 cm with or without pericolonic edema on CT suggests cancer rather than diverticulitis and requires colonoscopy. 2, 4
• Do not continue antibiotics beyond 7 days in uncomplicated cases, as this increases resistance without improving outcomes. 4
• If signs of infection persist beyond 7 days, obtain repeat imaging to assess for inadequate source control rather than extending antibiotics. 4
• Routine colonoscopy after CT-confirmed diverticulitis is not warranted except for age-appropriate screening, unless abscess, perforation, or fistula is present. 2

Special Considerations

• This approach does not apply to patients with recent antibiotic use, concomitant unstable comorbid conditions, immunosuppression, or signs of sepsis. 1
• Perforation or peritonitis requires emergent surgery. 2
• Outpatient management likely results in 35-83% cost savings per episode compared to hospitalization. 1