What is the initial treatment approach for an uncomplicated diverticulitis flare?

Work-Up for Diverticulitis Flare

Initial Diagnostic Approach

For suspected acute diverticulitis, obtain a contrast-enhanced CT scan of the abdomen and pelvis, which has 98-99% sensitivity and 99-100% specificity for diagnosis and is essential for distinguishing uncomplicated from complicated disease. 1

Laboratory Studies

• Complete blood count to assess for leukocytosis (WBC >13.5-15 × 10^9 cells/L suggests higher risk for progression) 2, 3
• C-reactive protein (CRP >140 mg/L indicates increased risk of complicated disease) 2, 3
• Basic metabolic panel to evaluate electrolyte abnormalities and renal function 1
• Urinalysis to exclude urinary tract infection as alternative diagnosis 4

CT Imaging Findings to Document

The CT scan should specifically evaluate for:

• Intestinal wall thickening and pericolonic fat stranding (confirms uncomplicated diverticulitis) 3
• Pericolic extraluminal air (predictor of progression to complicated disease) 2
• Fluid collections or abscess (size ≥4-5 cm requires percutaneous drainage) 3, 5
• Length of inflamed colon segment (longer segments predict worse outcomes) 2, 3
• Free air or peritonitis (requires emergent surgical consultation) 5, 1

Risk Stratification After Diagnosis

High-Risk Features Requiring Hospitalization

Admit patients with any of the following: 2, 5

• Complicated diverticulitis (abscess, perforation, fistula, obstruction, peritonitis)
• Inability to tolerate oral intake
• Severe pain requiring parenteral analgesia
• Signs of sepsis or systemic inflammatory response
• Immunocompromised status (chemotherapy, high-dose steroids, organ transplant)
• Significant comorbidities (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes)
• Age >80 years
• Pregnancy
• ASA score III or IV

Predictors of Progression to Complicated Disease

Document these risk factors as they guide treatment intensity: 2, 3

• Symptoms lasting >5 days before presentation
• Vomiting
• Pain score ≥7-8/10
• CRP >140 mg/L
• WBC >15 × 10^9 cells/L
• CT findings of fluid collection or longer inflamed segment

Treatment Algorithm Based on Risk Stratification

For Uncomplicated Diverticulitis in Immunocompetent Patients

Most immunocompetent patients with uncomplicated diverticulitis do NOT require antibiotics and should be managed with observation, clear liquid diet, and acetaminophen for pain control. 2, 6, 3 This recommendation is based on multiple high-quality RCTs showing no difference in complications, surgery rates, or recurrence between antibiotic and no-antibiotic groups. 2, 7

Reserve antibiotics for patients with:

• Persistent fever or chills 6, 1
• Increasing leukocytosis 6, 1
• Elevated inflammatory markers (CRP >140 mg/L, WBC >15 × 10^9/L) 6, 3
• Refractory symptoms or vomiting 6, 3
• Fluid collection or longer segment of inflammation on CT 6, 3

Outpatient Antibiotic Regimens (When Indicated)

First-line oral regimens for 4-7 days: 6, 3, 1

• Amoxicillin-clavulanate 875/125 mg twice daily, OR
• Ciprofloxacin 500 mg twice daily PLUS metronidazole 500 mg three times daily

Inpatient Management

For hospitalized patients, initiate IV antibiotics with gram-negative and anaerobic coverage: 6, 5, 1

• Ceftriaxone PLUS metronidazole, OR
• Piperacillin-tazobactam

Transition to oral antibiotics as soon as patient tolerates oral intake (typically within 48 hours, which facilitates earlier discharge). 6, 3

Duration of Antibiotic Therapy

• Immunocompetent patients: 4-7 days total 6, 3
• Immunocompromised patients: 10-14 days 6, 3
• Complicated diverticulitis with adequate drainage: 4 days post-procedure 6

Follow-Up Requirements

All outpatients require re-evaluation within 7 days, with earlier follow-up if clinical deterioration occurs. 6, 3 This is mandatory to detect progression to complicated disease.

Colonoscopy should be performed 4-6 weeks after symptom resolution for patients with complicated disease or those requiring age-appropriate screening to exclude malignancy or inflammatory bowel disease. 3, 4

Critical Pitfalls to Avoid

• Do not routinely prescribe antibiotics for all uncomplicated diverticulitis cases in immunocompetent patients, as this contributes to antibiotic resistance without improving outcomes 2, 6
• Do not delay CT imaging because it is the only reliable way to distinguish uncomplicated from complicated disease 1
• Do not miss immunocompromised status (including corticosteroid use), as these patients require antibiotics, longer treatment duration, and lower threshold for hospitalization 6, 3, 5
• Do not fail to recognize progression indicators (symptoms >5 days, vomiting, high inflammatory markers) that warrant antibiotic initiation even in initially selected patients 2, 3
• Do not discharge patients without ensuring reliable 7-day follow-up and clear return precautions 6, 3