Management of Acute Diverticulitis
For uncomplicated diverticulitis in immunocompetent patients without comorbidities, outpatient management without routine antibiotics is safe and effective, while complicated diverticulitis requires hospitalization with IV antibiotics and intervention based on severity. 1, 2
Initial Diagnostic Approach
Do not rely on clinical examination alone - it has poor accuracy with a positive predictive value of only 0.65 3, 4. CT scan of the abdomen and pelvis with IV and oral contrast is mandatory to distinguish uncomplicated from complicated disease, with sensitivity and specificity of 95% 3, 5. Clinical findings (left lower quadrant pain, fever, tenderness) combined with inflammatory markers (CRP, WBC) are insufficient for accurate diagnosis 6.
The Laméris criteria can support clinical diagnosis when all three are present: (1) direct tenderness only in the left lower quadrant, (2) CRP > 50 mg/L, and (3) absence of vomiting - this combination has 97% positive predictive value 6, 4.
Classification Framework
Use the WSES classification system to guide management 6, 1:
Uncomplicated Diverticulitis (Stage 0)
- Diverticula with bowel wall thickening and increased pericolic fat density
- No abscess, perforation, or distant complications
- Inflammation confined to colon wall 6, 1
Complicated Diverticulitis (Stages 1-4)
- Stage 1A: Pericolic air bubbles or small fluid collection within 5 cm of inflamed bowel 6
- Stage 1B: Abscess ≤ 4 cm 6
- Stage 2A: Abscess > 4 cm 6
- Stage 2B: Distant gas (> 5 cm from inflamed segment) 6
- Stage 3: Diffuse fluid without distant free gas 6
- Stage 4: Diffuse fluid with distant free gas (generalized peritonitis) 6
Management Algorithm for Uncomplicated Diverticulitis
Outpatient management is appropriate for immunocompetent patients without severe comorbidities 1, 7, 8. Success rates range from 91.5-100% with fewer than 8% requiring readmission 7, 8.
When to Treat Outpatient
- Immunocompetent status
- Tolerating oral intake
- Reliable follow-up available
- No severe systemic inflammatory response
- Adequate social support 1, 7, 8
Antibiotic Use in Uncomplicated Disease
Antibiotics may be safely omitted in select patients with uncomplicated diverticulitis 1, 2. Multiple high-quality RCTs (AVOD, DIABLO, DINAMO, STAND) demonstrated no difference in morbidity, mortality, or complication rates between antibiotic and non-antibiotic management 2. The ASCRS and AAFP now recommend against routine antibiotics for acute uncomplicated diverticulitis 2.
Consider antibiotics if:
- Immunocompromised state
- Significant comorbidities
- Systemic inflammatory response present
- Clinical deterioration 1, 9
Red Flags Requiring Hospitalization
Watch for predictors of progression to complicated disease 1, 4:
- Symptoms lasting > 5 days
- Pain score ≥ 8 on visual analog scale
- Vomiting
- CRP > 140 mg/L
- Age < 50 years
- Intolerance to oral intake 1, 4, 8
Important caveat: Approximately 5% of patients with severe diverticulitis present without fever or leukocytosis - do not be falsely reassured by normal vital signs or WBC 1.
Management Algorithm for Complicated Diverticulitis
Hospitalization is mandatory for all complicated presentations 1, 3.
IV Antibiotic Therapy
Broad-spectrum IV antibiotics covering gram-negative and anaerobic organisms are required for all complicated cases 1, 3. Continue until clinical improvement, then transition to oral therapy.
Intervention Based on Stage
Stage 1A (pericolic air bubbles/small fluid):
- IV antibiotics
- Close monitoring
- No drainage needed 6
Stage 1B-2A (abscess ≤ 4 cm to > 4 cm):
- IV antibiotics
- Percutaneous CT-guided drainage for abscesses > 4 cm 1, 3
- Abscesses ≥ 3-4 cm are amenable to drainage 3
Stage 2B-3 (distant gas, diffuse fluid without free gas):
- IV antibiotics
- Percutaneous drainage if accessible abscess
- Consider surgical consultation 6
Stage 4 (generalized peritonitis):
- Urgent surgical intervention required 1
- Laparoscopic approach preferred when feasible - results in shorter hospital stay, fewer complications, and lower mortality compared to open colectomy 9
- Options include primary resection with anastomosis or Hartmann's procedure depending on severity 4
Critical Pitfalls to Avoid
- Never perform colonoscopy during acute diverticulitis - wait 6-8 weeks after symptom resolution due to perforation risk 3
- Do not underestimate severity in younger patients (age < 50 is a risk factor for progression) 1, 4
- Do not delay CT imaging in favor of clinical observation alone 3, 4
- Do not assume absence of fever or leukocytosis rules out severe disease 1
- Do not routinely prescribe antibiotics for uncomplicated disease in immunocompetent patients 1, 2
Follow-up Considerations
Colonoscopy is recommended 6-8 weeks after resolution for patients with complicated disease or those requiring age-appropriate screening to exclude malignancy 3, 9. CT imaging alone cannot reliably distinguish diverticulitis from colonic malignancy in all cases 5.