Diagnostic Workup, Presentation, and Treatment of Diverticulitis
Clinical Presentation and Diagnosis
Acute diverticulitis typically presents as left lower quadrant pain associated with nausea, vomiting, fever, and leukocytosis. 1
Diagnostic Imaging
- Contrast-enhanced CT scan of the abdomen and pelvis is the gold standard diagnostic test, with sensitivity of 98-99% and specificity of 99-100%. 1
- CT findings include diverticula, colonic wall thickening (>4 mm), increased density of pericolic fat, and in complicated cases: abscess, free intraperitoneal fluid, extraluminal gas, or perforation. 2, 3
- For elderly patients who cannot receive IV contrast (due to renal insufficiency or contrast allergy), alternative imaging includes ultrasound, MRI, or unenhanced CT, though these are less accurate for detecting complications. 2
- Point-of-care ultrasound (POCUS) can identify wall thickening >4 mm, non-compressibility, loss of peristalsis, and complications like abscess or free air in patients unable to undergo CT. 2
Classification
- Uncomplicated diverticulitis (85% of cases): Localized inflammation without abscess, perforation, fistula, or obstruction. 1, 3
- Complicated diverticulitis (15% of cases): Presence of abscess, perforation, fistula, obstruction, or generalized peritonitis. 3
Treatment Algorithm for Uncomplicated Diverticulitis
First-Line Management for Immunocompetent Patients
For immunocompetent patients with uncomplicated diverticulitis, observation without antibiotics is the recommended first-line treatment. 4, 3
- Clear liquid diet during the acute phase, advancing as symptoms improve. 4, 3
- Pain control with acetaminophen (avoid NSAIDs and opioids as they increase risk of complications). 1, 4
- Antibiotics do not accelerate recovery, prevent complications, or reduce recurrence rates in this population. 2
Indications for Antibiotic Therapy in Uncomplicated Diverticulitis
Antibiotics should be reserved for patients with specific high-risk features:
- Immunocompromised status (chemotherapy, high-dose steroids, organ transplant recipients). 1, 4
- Age >80 years. 1, 4
- Pregnancy. 1
- Systemic symptoms: persistent fever, chills, or signs of sepsis. 1, 4
- Increasing leukocytosis (WBC >15 × 10⁹/L). 4, 3
- Elevated inflammatory markers (CRP >140 mg/L). 4, 3
- CT findings of fluid collection or longer segment of inflammation. 4, 3
- Significant comorbidities: cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes. 1
- Refractory symptoms or vomiting. 4
Antibiotic Regimens When Indicated
Outpatient oral regimens (4-7 days for immunocompetent patients):
- Amoxicillin-clavulanate (preferred single agent). 4, 1
- Ciprofloxacin 500 mg twice daily plus metronidazole 500 mg three times daily. 4, 5
Inpatient IV regimens:
Duration:
Treatment of Complicated Diverticulitis
Localized Complicated Diverticulitis (WSES Stage 1a)
For elderly patients with pericolic air bubbles or minimal pericolic fluid without abscess, antibiotic therapy is recommended. 2
Diverticular Abscess Management
For abscesses <4 cm: Antibiotic therapy alone for 7 days. 2, 3
For abscesses ≥4-5 cm: Percutaneous drainage combined with antibiotic therapy for 4 days (when skills and facilities are available). 2, 4
- Cultures from drainage should guide antibiotic selection. 2
- Failure rate for antibiotics alone is 18.7% for small abscesses; percutaneous drainage fails in 21.1% of larger abscesses. 2
Distant Free Intraperitoneal Air (WSES Stage 2b)
In elderly patients with distant free air and no diffuse fluid, non-operative management is NOT recommended—surgical exploration is indicated. 2
- Non-operative management in this setting has high failure rates (10-43%). 2
Diffuse Peritonitis (WSES Stage 3-4)
Patients with generalized peritonitis require emergent laparotomy with colonic resection. 1
- IV antibiotics: piperacillin-tazobactam, meropenem, or ceftriaxone plus metronidazole. 5, 1
- Postoperative mortality: 0.5% for elective resection vs. 10.6% for emergent resection. 1
Inpatient vs. Outpatient Management
Criteria for Outpatient Management
Outpatient treatment is appropriate for patients who:
- Have uncomplicated diverticulitis. 4, 6
- Can tolerate oral intake. 4, 6
- Have no significant comorbidities or frailty. 4
- Have adequate home support and can manage self-care. 4
- Are immunocompetent. 4
Outpatient management reduces costs by 35-83% per episode and decreases risk of hospital-acquired infections. 4
Criteria for Inpatient Management
Hospitalization is required for:
- Complicated diverticulitis (abscess, perforation, obstruction). 4, 3
- Inability to tolerate oral intake. 4, 3
- Severe pain or systemic symptoms (sepsis, septic shock). 4, 3
- Significant comorbidities or frailty. 4
- Immunocompromised status. 4
Transition from IV to oral antibiotics should occur as soon as the patient can tolerate oral intake to facilitate earlier discharge. 4, 5
Follow-Up and Monitoring
- Re-evaluation within 7 days is mandatory; earlier if clinical condition deteriorates. 4, 3
- Monitor for warning signs requiring immediate attention: fever >101°F, severe uncontrolled pain, persistent vomiting, inability to eat/drink, signs of dehydration. 4
- Colonoscopy is NOT routinely recommended after CT-proven uncomplicated diverticulitis, but should be considered for patients with diverticular abscesses to rule out underlying malignancy. 3
Prevention of Recurrence
- High-quality diet: High in fiber from fruits, vegetables, whole grains, legumes; low in red meat and sweets. 4
- Regular physical activity, particularly vigorous exercise. 4
- Achieve or maintain normal body mass index. 4
- Avoid smoking. 4
- Avoid regular use of NSAIDs and opioids, as these increase risk of diverticulitis. 4
- Do NOT restrict nuts, corn, popcorn, or small-seeded fruits—these are not associated with increased risk. 2, 4
Common Pitfalls to Avoid
- Overusing antibiotics in immunocompetent patients with uncomplicated diverticulitis provides no benefit and contributes to antibiotic resistance. 2, 3
- Failing to recognize high-risk patients who need antibiotics despite having uncomplicated disease can lead to progression to complicated diverticulitis. 5, 3
- Stopping antibiotics early, even if symptoms improve, may lead to incomplete treatment and recurrence. 4
- Assuming all elderly patients require antibiotics—the decision should be based on specific risk factors, not age alone. 2
- Overlooking immunocompromised status, which requires longer antibiotic duration (10-14 days) and lower threshold for hospitalization. 4, 5
- Unnecessarily restricting diet (avoiding nuts, seeds, popcorn) is not evidence-based and may reduce overall fiber intake. 4