Treatment of Acute Diverticulitis Flare

Classification and Diagnosis

Uncomplicated diverticulitis is defined as localized diverticular inflammation without abscess or perforation, typically confirmed by CT scan showing diverticula, wall thickening, and increased density of pericolic fat 1
Complicated diverticulitis involves abscess formation, perforation, fistula, or obstruction 1

For immunocompetent patients with uncomplicated diverticulitis, antibiotics are not recommended as first-line therapy, and management should focus on supportive care with clear liquid diet and pain control 1, 2
Clear liquid diet during the acute phase, advancing as symptoms improve 2
Observation without antibiotics for immunocompetent patients with mild uncomplicated diverticulitis 1, 2
Re-evaluation within 7 days; earlier if clinical condition deteriorates 3

Antibiotics should be reserved for patients with systemic manifestations of infection 1, 2
Antibiotics should be reserved for patients with immunocompromised status 2
Antibiotics should be reserved for patients with advanced age (>80 years) 2
Antibiotics should be reserved for patients with significant comorbidities 1, 2
Antibiotics should be reserved for patients with CRP >140 mg/L or WBC >15 × 10^9/L 2
Antibiotics should be reserved for patients with longer segment of inflammation or fluid collection on CT 2

Oral antibiotics are preferred whenever possible 1
Duration: 4-7 days for immunocompetent patients; up to 7 days for immunocompromised or critically ill patients 4

For small abscesses (<4-5 cm), antibiotic therapy alone for 7 days 4, 5
For large abscesses (>4-5 cm), percutaneous drainage combined with antibiotic therapy for 4 days 4, 5
Surgical intervention if clinical deterioration occurs 5

Failure to recognize high-risk patients who need antibiotics despite having uncomplicated disease can lead to progression to complicated diverticulitis 2
Unnecessary use of antibiotics in low-risk patients with uncomplicated diverticulitis provides no benefit and contributes to antibiotic resistance 1, 7
Young patients (<50 years) and those with high pain scores (≥8/10) have increased risk for complicated or recurrent diverticulitis and should be monitored more closely 8
The transition from IV to oral antibiotics should be made as soon as possible to facilitate earlier discharge 1
Follow-up colonoscopy is not routinely recommended for CT-proven uncomplicated diverticulitis but should be considered for patients with diverticular abscesses to rule out underlying malignancy 5

CT abdomen‑pelvis with intravenous contrast provides very high diagnostic accuracy for acute diverticulitis, with a sensitivity of 98–99 % and a specificity of 99–100 %. This performance supports its use as the primary imaging modality to confirm the diagnosis, stage disease severity, and exclude complications. American College of Radiology recommendation. 9
Uncomplicated diverticulitis on CT is defined by the presence of diverticula, colonic wall thickening, and increased pericolic fat density without abscess, perforation, fistula, obstruction, or free intraperitoneal air. Recognizing these features allows clinicians to select patients for outpatient observation without routine antibiotics. World Journal of Emergency Surgery criteria. 10
Complicated diverticulitis on CT is identified by any of the following findings: abscess formation, extraluminal gas, perforation, fistula, obstruction, or distant free fluid. Detection of these signs mandates immediate antimicrobial therapy and consideration of interventional or surgical management. World Journal of Emergency Surgery criteria. 10

A complete blood count (CBC) and C‑reactive protein (CRP) measurement should be obtained in all patients with suspected acute diverticulitis. These laboratory tests help quantify the inflammatory burden and guide risk stratification, influencing decisions about hospitalization, antibiotic use, and close monitoring. World Journal of Emergency Surgery recommendation. [11][12]