What is the recommended diagnosis and management approach for diverticulitis?

Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis

Diagnostic Approach

For patients presenting with left lower quadrant pain, fever, and leukocytosis, obtain a contrast-enhanced CT scan of the abdomen and pelvis, which has 98-99% sensitivity and 99-100% specificity for diagnosing acute diverticulitis. 1

Key Diagnostic Considerations:

• Laboratory studies should include complete blood count, C-reactive protein (CRP), and basic metabolic panel 2
• CT imaging establishes diagnosis, determines extent and severity, and differentiates uncomplicated from complicated disease 3, 2
• Uncomplicated diverticulitis = localized inflammation without abscess, phlegmon, fistula, obstruction, bleeding, or perforation 3
• Complicated diverticulitis = inflammation with abscess, phlegmon, fistula, obstruction, bleeding, or perforation 3

Predictors of Progression to Complicated Disease:

• Symptoms lasting >5 days 3
• Initial pain score >7 3
• Vomiting 3
• CRP >140 mg/L 3
• White blood cell count >13.5 × 10⁹ cells/L 3
• CT findings of pericolic extraluminal air, fluid collection, or longer inflamed colon segment 3

---

Management of Uncomplicated Diverticulitis

Initial Treatment Strategy

For immunocompetent patients with acute uncomplicated left-sided colonic diverticulitis, manage initially without antibiotics using observation with supportive care (bowel rest, clear liquid diet, and acetaminophen for pain). 3, 4, 1

This recommendation is based on low-certainty evidence showing no differences in quality of life, diverticulitis-related complications (abscess, fistula, stenosis, obstruction), need for surgery, or long-term recurrence between antibiotic and non-antibiotic groups 3. The evidence challenges the traditional infectious etiology, suggesting diverticulitis is primarily an inflammatory process 3.

Outpatient vs. Inpatient Management

Manage most patients with uncomplicated diverticulitis in an outpatient setting. 3, 4

Outpatient management is appropriate when patients:

• Can tolerate oral fluids and medications 5
• Have no significant comorbidities or frailty 3, 5
• Have adequate home and social support 3
• Are afebrile or have temperature <100.4°F 5
• Have no signs of systemic inflammatory response or sepsis 3

Outpatient management results in 35-83% cost savings per episode compared to hospitalization, with no increase in complications 3. The outpatient failure rate is only 4.3% 4.

Hospitalization is required for:

• Complicated diverticulitis 3
• Inability to tolerate oral intake 3
• Signs of peritonitis or sepsis 3, 2
• Immunocompromised status 3
• Significant comorbidities or frailty 3
• Severe pain or systemic symptoms 4

---

Selective Antibiotic Use in Uncomplicated Diverticulitis

When to Use Antibiotics

Reserve antibiotics for select patients with uncomplicated diverticulitis who have specific risk factors. 3, 5

Antibiotic indications include:

• Immunocompromised status (chemotherapy, high-dose steroids, organ transplant) 3, 1
• Age >80 years 1
• Pregnancy 1
• Persistent fever or chills 1
• Increasing leukocytosis 5, 1
• CRP >140 mg/L 5
• White blood cell count >15 × 10⁹ cells/L 5
• Fluid collection or longer segment of inflammation on CT 5
• Vomiting or inability to maintain hydration 3, 5
• Chronic medical conditions (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 1
• ASA score III or IV 5

Antibiotic Regimens and Duration

For outpatient treatment requiring antibiotics:

• First-line oral regimen: Ciprofloxacin 500 mg twice daily PLUS metronidazole 500 mg three times daily for 4-7 days 5, 6, 1
• Alternative oral regimen: Amoxicillin-clavulanate 875/125 mg twice daily for 4-7 days 5, 1

For inpatient treatment requiring IV antibiotics:

• Ceftriaxone PLUS metronidazole 5, 1
• Cefuroxime PLUS metronidazole 6, 1
• Piperacillin-tazobactam 5, 1
• Ampicillin-sulbactam 6, 1

Transition from IV to oral antibiotics as soon as the patient tolerates oral intake to facilitate earlier discharge (typically within 48 hours) 3, 5.

Duration of antibiotic therapy:

• Immunocompetent patients: 4-7 days 5, 6
• Immunocompromised patients: 10-14 days 5, 6

---

Management of Complicated Diverticulitis

Abscess Management

For abscesses ≥4-5 cm, perform percutaneous CT-guided drainage combined with antibiotic therapy. 5, 4

For abscesses <4-5 cm, attempt initial non-operative management with antibiotics alone (pooled failure rate 20%, mortality 0.6%) 4.

Antibiotic Regimens for Complicated Disease

Initiate IV antibiotics with gram-negative and anaerobic coverage:

• Ceftriaxone PLUS metronidazole 1
• Piperacillin-tazobactam 1

For critically ill or immunocompromised patients with septic shock:

• Meropenem 6
• Doripenem 6
• Imipenem-cilastatin 6
• Eravacycline 6

Duration: 4 days after adequate source control in immunocompetent patients; 7-14 days for immunocompromised or critically ill patients 5, 6.

Surgical Management

Patients with generalized peritonitis require emergent laparotomy with colonic resection. 1

Mortality rates: 0.5% for elective colon resection vs. 10.6% for emergent colon resection 1. Laparoscopic surgery results in shorter length of stay, fewer complications, and lower in-hospital mortality compared to open colectomy 2.

---

Follow-Up and Prevention

Colonoscopy

Perform colonoscopy 4-6 weeks after resolution of symptoms for patients with complicated diverticulitis or those without a high-quality colonoscopy in the past year. 4, 2

This excludes alternative diagnoses such as inflammatory bowel disease, ischemic colitis, or malignancy 5.

Prevention of Recurrence

Recommend the following lifestyle modifications:

• High-quality diet: High in fiber from fruits, vegetables, whole grains, and legumes; low in red meat and sweets 5, 4
• Regular physical activity, particularly vigorous exercise 5, 4
• Achieve or maintain normal body mass index 5
• Smoking cessation 5, 2
• Avoid regular use of NSAIDs and opioids when possible 5

Do NOT restrict consumption of nuts, corn, popcorn, or small-seeded fruits (not associated with increased diverticulitis risk) 5, 4.

Re-evaluation Timing

Re-evaluate patients within 7 days of diagnosis; earlier if clinical condition deteriorates. 5, 4

---

Common Pitfalls to Avoid

• Overusing antibiotics in uncomplicated diverticulitis without risk factors contributes to antibiotic resistance without clinical benefit 3, 4
• Failing to recognize high-risk features (prolonged symptoms, vomiting, elevated inflammatory markers, CT findings) that predict progression to complicated disease 3, 4
• Assuming all patients require hospitalization when most can be safely managed as outpatients with appropriate follow-up 3, 4
• Stopping antibiotics early even if symptoms improve, which may lead to incomplete treatment 5
• Unnecessarily restricting diet (avoiding nuts, seeds, popcorn) which is not evidence-based and may reduce overall fiber intake 5, 4
• Failing to establish reliable follow-up mechanisms for outpatient management 5