What is the treatment for a patient with diverticulitis?

Diverticulitis: Definition and Treatment

What is Diverticulitis?

Diverticulitis is inflammation and/or infection of colonic diverticula (outpouchings from the intestinal wall), typically presenting as left lower quadrant abdominal pain with fever, nausea, vomiting, and leukocytosis. 1

• Diverticulitis affects approximately 180 per 100,000 people annually in the US, resulting in over 200,000 hospital admissions and $6.3 billion in healthcare costs 1
• Only 1-4% of patients with diverticulosis (presence of diverticula without inflammation) will develop acute diverticulitis in their lifetime 1
• Approximately 85% of cases are uncomplicated (localized inflammation without abscess, perforation, fistula, or obstruction), while 15% are complicated 1, 2

Treatment Algorithm

Step 1: Confirm Diagnosis and Classify Severity

• CT scan with IV contrast is the gold standard diagnostic test with 98-99% sensitivity and 99-100% specificity 1, 2
• Obtain complete blood count, C-reactive protein, and basic metabolic panel to assess disease severity 3, 2
• Classify as uncomplicated versus complicated based on CT findings (presence of abscess, perforation, fistula, or obstruction) 1, 2

Step 2: Determine Inpatient vs Outpatient Management

Outpatient management is appropriate when ALL criteria are met: 2, 4

• Ability to tolerate oral fluids and medications
• No significant comorbidities or frailty
• Adequate home and social support
• Temperature <100.4°F
• Pain controlled with acetaminophen alone (pain score <4/10)

Hospitalization is required for: 2, 4

• Complicated diverticulitis (abscess, perforation, peritonitis)
• Inability to tolerate oral intake
• Severe pain or systemic symptoms (sepsis)
• Immunocompromised status
• Significant comorbidities (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes)

Step 3: Antibiotic Decision for Uncomplicated Diverticulitis

Most immunocompetent patients with uncomplicated diverticulitis do NOT require antibiotics—observation with supportive care is first-line therapy. 2, 4, 1

Reserve antibiotics ONLY for patients with these specific risk factors: 2, 1

• Immunocompromised status (chemotherapy, high-dose steroids, organ transplant)
• Age >80 years
• Pregnancy
• Persistent fever or chills despite supportive care
• Increasing leukocytosis or CRP >140 mg/L
• White blood cell count >15 × 10⁹ cells/L
• Vomiting or inability to maintain hydration
• Symptoms lasting >5 days
• CT findings of pericolic extraluminal air, fluid collection, or longer inflamed segment
• ASA score III or IV
• Significant comorbidities (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes)

This selective approach is based on high-quality evidence showing antibiotics neither accelerate recovery nor prevent complications or recurrence in uncomplicated cases. 2, 4

Step 4: Antibiotic Regimens When Indicated

Outpatient oral regimens (4-7 days for immunocompetent patients): 2, 1

• First-line: Ciprofloxacin 500 mg twice daily PLUS metronidazole 500 mg three times daily
• Alternative: Amoxicillin-clavulanate 875/125 mg twice daily

Inpatient IV regimens (transition to oral as soon as tolerated): 2, 1

• Ceftriaxone PLUS metronidazole
• Piperacillin-tazobactam

Duration of therapy: 2

• 4-7 days for immunocompetent patients with uncomplicated disease
• 10-14 days for immunocompromised patients
• 4 days post-drainage for complicated diverticulitis with adequate source control

Step 5: Management of Complicated Diverticulitis

For abscesses: 2, 4

• Small abscesses (<4-5 cm): IV antibiotics alone may be sufficient (20% failure rate)
• Large abscesses (≥4-5 cm): Percutaneous CT-guided drainage PLUS IV antibiotics

For generalized peritonitis or sepsis: 2, 4

• Emergent surgical consultation
• IV antibiotics with broad-spectrum coverage
• Source control surgery (Hartmann's procedure or primary resection with anastomosis)

Step 6: Supportive Care

For all patients with acute diverticulitis: 2, 4

• Clear liquid diet during acute phase, advancing as symptoms improve
• Pain control with acetaminophen (avoid NSAIDs and opioids when possible)
• Bowel rest initially

Step 7: Follow-Up and Monitoring

• Re-evaluation within 7 days is mandatory, earlier if clinical condition deteriorates 2, 4
• Colonoscopy 4-6 weeks after symptom resolution for patients with complicated diverticulitis or first episode in patients >50 years who haven't had recent high-quality colonoscopy (to exclude malignancy—risk is 7.9% in complicated cases) 2, 3

Step 8: Prevention of Recurrence

Evidence-based lifestyle modifications: 2, 4

• High-quality diet rich in fiber from fruits, vegetables, whole grains, and legumes (>22.1 g/day)
• Low intake of red meat and sweets
• Regular vigorous physical activity
• Achieve or maintain BMI 18-25 kg/m²
• Smoking cessation
• Avoid regular use of NSAIDs and opioids when possible

Important: Restricting nuts, corn, popcorn, or small-seeded fruits is NOT necessary—these are not associated with increased diverticulitis risk 2, 4

Critical Pitfalls to Avoid

• Do not routinely prescribe antibiotics for uncomplicated diverticulitis in immunocompetent patients without risk factors—this contributes to antibiotic resistance without clinical benefit 2, 4
• Do not assume all patients require hospitalization—outpatient management is safe with only 4.3% failure rate and results in 35-83% cost savings 2, 4
• Do not stop antibiotics early if they are indicated, even if symptoms improve 2
• Do not delay surgical consultation in patients with frequent recurrences significantly impacting quality of life 2
• Do not prescribe mesalamine or rifaximin for prevention—high-quality evidence shows no benefit 2
• Do not base elective surgery decisions solely on number of episodes—individualize based on quality of life impact, frequency, and patient preferences 2, 4