Management of Acute Diverticulitis

Initial Diagnostic Confirmation

For patients presenting with suspected acute diverticulitis, obtain a contrast-enhanced CT scan of the abdomen and pelvis to confirm the diagnosis and classify disease severity—clinical examination alone is unreliable with only 65% positive predictive value. 1, 2

CT imaging with IV contrast is essential to distinguish uncomplicated from complicated disease and should not be omitted, as clinical examination has poor accuracy (sensitivity 0.68, specificity 0.98). 2
The Laméris criteria (left lower quadrant tenderness and CRP > 50 mg/L and absence of vomiting) provide 97% positive predictive value when all three are present, but imaging remains necessary for classification. 2, 3
Imaging may be deferred only in patients with prior imaging-confirmed diverticulitis presenting with mild recurrent symptoms consistent with their previous episodes. 1

Classification Using WSES System

Use the World Society of Emergency Surgery (WSES) classification to stratify severity and guide treatment decisions: 2, 4

Uncomplicated Diverticulitis (Stage 0)

Diverticula with bowel wall thickening and increased pericolic fat density without abscess, perforation, or distant complications. 2

Complicated Diverticulitis (Stages 1-4)

Stage 1A: Pericolic air bubbles or small fluid collection ≤5 cm from inflamed segment. 2
Stage 1B: Abscess ≤4 cm diameter. 2
Stage 2A: Abscess >4 cm diameter. 2
Stage 2B: Distant free gas >5 cm from inflamed bowel. 2
Stage 3: Diffuse intra-abdominal fluid without distant free gas. 2
Stage 4: Diffuse fluid with distant free gas (generalized peritonitis). 2

Management of Uncomplicated Diverticulitis

For immunocompetent patients with uncomplicated diverticulitis (Stage 0), manage as outpatient with observation, pain control using acetaminophen, and clear liquid diet—antibiotics are not routinely necessary. 1, 5

Outpatient Management Criteria

Immunocompetent status without significant comorbidities. 1
Ability to tolerate oral intake. 5
Reliable follow-up available. 1
No systemic symptoms (persistent fever, chills, increasing leukocytosis). 5

When to Prescribe Antibiotics for Uncomplicated Disease

Reserve antibiotics for patients with: 5

Persistent fever or chills despite initial management
Increasing leukocytosis on serial monitoring
Age >80 years
Pregnancy
Immunocompromise (chemotherapy, high-dose steroids, organ transplant)
Chronic medical conditions (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes)

First-line oral antibiotics: Amoxicillin/clavulanic acid OR cefalexin plus metronidazole. 5

Red Flags Requiring Hospitalization

Admit patients with: 2, 3

Symptoms lasting >5 days
Severe pain (VAS ≥8)
Vomiting
CRP >140 mg/L
Age <50 years (higher risk of progression)
Signs of peritonitis on examination

Management of Complicated Diverticulitis

All patients with complicated diverticulitis require hospitalization, IV fluid resuscitation, and broad-spectrum IV antibiotics covering gram-negative and anaerobic organisms. 2, 6

Stage-Specific Treatment Algorithm

Stage 1A (Pericolic air/small fluid collection ≤5 cm)

IV antibiotics (ceftriaxone plus metronidazole OR piperacillin-tazobactam). 5
Close monitoring with serial examinations. 2
No percutaneous drainage required. 2

Stage 1B (Abscess ≤4 cm)

IV antibiotics alone. 2
Drainage generally not needed. 2
Monitor for clinical improvement within 48-72 hours. 6

Stage 2A (Abscess >4 cm)

IV antibiotics PLUS CT-guided percutaneous drainage. 2, 5
Percutaneous drainage allows for potential one-stage resection if surgery becomes necessary. 7

Stage 2B (Distant free gas >5 cm)

IV antibiotics. 2
Obtain immediate surgical consultation. 2
Consider percutaneous drainage if accessible abscess present. 2
Hemodynamically stable patients without diffuse peritonitis may be managed non-operatively, but failure rate is 57-60% with large amounts of distant air. 1

Stage 3 (Diffuse fluid without distant free gas)

IV antibiotics. 2
Surgical consultation advised. 2
Percutaneous drainage if abscess present and accessible. 2

Stage 4 (Generalized peritonitis with distant free gas)

IV antibiotics AND urgent surgical intervention. 2, 5
Laparoscopic approach preferred when feasible (shorter length of stay, fewer complications, lower mortality compared to open). 6
Resection with primary anastomosis preferred over Hartmann's procedure when patient is hemodynamically stable. 7
Emergent laparotomy required for patients with septic shock or hemodynamic instability. 5

Antibiotic Regimens for Complicated Disease

IV options: 5

Ceftriaxone plus metronidazole
Cefuroxime plus metronidazole
Piperacillin-tazobactam
Ampicillin/sulbactam

Continue IV antibiotics until clinical improvement (afebrile, tolerating diet, normalizing WBC), then transition to oral therapy to complete 7-10 day course. 6

Surgical Considerations

Indications for Emergent Surgery

Generalized peritonitis (Stage 4). 2, 5
Hemodynamic instability or septic shock. 5
Failure of non-operative management (persistent or worsening symptoms after 48-72 hours). 6

Mortality Rates

Elective colon resection: 0.5% mortality. 5
Emergent colon resection: 10.6% mortality. 5

Timing of Elective Surgery

Elective resection should be performed 6-8 weeks after resolution of acute episode. 8
Decision should be personalized based on severity, patient preferences, and comorbidities—not based solely on number of episodes. 1
Laparoscopic approach preferred for elective cases. 8, 6

Common Pitfalls to Avoid

Underestimating severity in younger patients (<50 years have higher risk of progression). 2, 3
Delaying CT imaging in patients without prior imaging-confirmed diagnosis. 1, 2
Ignoring absence of fever or leukocytosis—5% of patients with severe diverticulitis present without these findings. 2
Prescribing antibiotics reflexively for all uncomplicated cases—reserve for high-risk patients only. 1, 5
Performing emergent surgery when percutaneous drainage is feasible—drainage allows for safer one-stage resection later. 7

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