Management of Left-Sided Diverticulitis

Diagnosis and Initial Assessment

Obtain a CT scan with intravenous contrast in all patients with suspected acute diverticulitis to confirm the diagnosis, distinguish uncomplicated from complicated disease, and guide management decisions. 1, 2 CT achieves 98–99% sensitivity and 99–100% specificity, and clinical assessment alone misclassifies 34–68% of cases. 2

Laboratory Work-Up

Complete blood count, C-reactive protein, and basic metabolic panel should be obtained in all patients to assess disease severity and guide risk stratification. 1, 2
CRP >140 mg/L and WBC >15 × 10⁹/L are high-risk laboratory markers that predict progression to complicated disease. 1, 2

Disease Classification

Uncomplicated diverticulitis: Localized colonic inflammation without abscess, perforation, fistula, obstruction, or bleeding. 1, 2, 3
Complicated diverticulitis: Presence of abscess, perforation, fistula, obstruction, or bleeding. 1, 2

Outpatient vs. Inpatient Management

Outpatient Management Criteria (ALL Must Be Met)

Most immunocompetent patients with uncomplicated diverticulitis can be safely managed as outpatients without routine antibiotics. 1, 2, 3 This approach is supported by the DIABOLO trial (528 patients), which demonstrated that antibiotics neither accelerate recovery nor prevent complications or recurrence in uncomplicated cases. 2, 3

Outpatient eligibility requires:

CT-confirmed uncomplicated disease (no abscess, perforation, fistula, or obstruction) 1, 2, 3
Ability to tolerate oral fluids and medications 1, 2, 3
Temperature <100.4°F (38°C) 2, 3
Pain score <4/10 controlled with acetaminophen alone 2, 3
No significant comorbidities (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 1, 2, 3
Immunocompetent status 1, 2, 3
Adequate home and social support 1, 2, 3

Outpatient management yields 35–83% cost savings per episode without compromising safety, with only 4.3% requiring subsequent hospitalization. 1, 2

Inpatient Management Indications

Hospitalize patients with any of the following:

Complicated diverticulitis on CT (abscess ≥4–5 cm, perforation, fistula, obstruction) 1, 2, 4
Inability to tolerate oral intake or persistent vomiting 1, 2, 4
Signs of systemic inflammatory response or sepsis (fever, tachycardia, hypotension) 1, 2, 4
Immunocompromised status (chemotherapy, high-dose steroids >20 mg prednisone daily, organ transplant) 1, 2, 4
Age >80 years 1, 2
Pregnancy 1, 2
Significant comorbidities or frailty (ASA III–IV) 1, 2, 4
Pain score ≥8/10 at presentation 2

Antibiotic Selection and Duration

When to Withhold Antibiotics

For immunocompetent patients with uncomplicated diverticulitis, first-line therapy is observation with supportive care (clear liquid diet, oral hydration, acetaminophen for pain) WITHOUT routine antibiotics. 1, 2, 3 The DIABOLO trial showed no benefit of antibiotics on recovery time, complication rates, or recurrence at 24-month follow-up, and hospital stays were actually shorter in the observation group (2 vs. 3 days). 2, 3

High-Risk Features Requiring Antibiotics

Reserve antibiotics for patients with ANY of the following high-risk features:

Clinical indicators:

Persistent fever >100.4°F or chills despite supportive care 1, 2, 3
Refractory symptoms or vomiting preventing oral hydration 1, 2, 3
Symptom duration >5 days before presentation 1, 2, 3

Laboratory indicators:

CRP >140 mg/L 1, 2, 3
WBC >15 × 10⁹/L or rising leukocytosis 1, 2, 3

CT imaging indicators:

Fluid collection or abscess 1, 2, 3
Longer segment of inflammation (>5 cm) 1, 2, 3
Pericolic extraluminal air 1, 2, 3

Patient factors:

Immunocompromised status (chemotherapy, high-dose steroids, organ transplant) 1, 2, 3
Age >80 years 1, 2, 3
Pregnancy 1, 2, 3
ASA physical status III–IV 1, 2, 3
Significant comorbidities (cirrhosis, CKD, heart failure, poorly controlled diabetes) 1, 2, 3

Antibiotic Regimens

Outpatient Oral Therapy (4–7 days for immunocompetent patients):

First-line: Amoxicillin-clavulanate 875/125 mg PO twice daily 2, 3, 5
Alternative: Ciprofloxacin 500 mg PO twice daily PLUS Metronidazole 500 mg PO three times daily 2, 3, 5

Inpatient IV Therapy (transition to oral within 48 hours when tolerated):

Ceftriaxone PLUS Metronidazole 2, 3, 4, 5
Piperacillin-tazobactam 2, 3, 4, 5
Amoxicillin-clavulanate 1.2 g IV every 6 hours 2

Duration of Therapy:

Immunocompetent patients: 4–7 days total 2, 3, 4
Immunocompromised patients: 10–14 days total 2, 3, 4
Post-percutaneous drainage: 4 days after adequate source control 2, 3

Transition from IV to oral antibiotics as soon as the patient tolerates oral intake (typically within 48 hours) to facilitate earlier discharge. 2, 3, 4

Management of Complicated Diverticulitis

Small Abscess (<4–5 cm)

Treat with IV antibiotics alone for 7 days. 2, 3 Hospitalization is required for close monitoring. 4

Large Abscess (≥4–5 cm)

Perform CT-guided percutaneous drainage PLUS IV antibiotics; continue antibiotics for 4 days after successful source control in immunocompetent patients. 2, 3, 4 Cultures from drainage should guide antibiotic selection. 2

Generalized Peritonitis or Sepsis

Obtain emergent surgical consultation for source control (Hartmann procedure or primary resection with anastomosis) and start broad-spectrum IV antibiotics immediately (piperacillin-tazobactam or ceftriaxone plus metronidazole). 2, 3, 4, 5

Diet Progression

Acute Phase

During the acute phase, advise a clear liquid diet for 2–3 days, then advance as symptoms improve. 2, 3 This recommendation is based primarily on patient comfort, as many patients present with anorexia and malaise. 2

If unable to advance diet after 3–5 days, immediate follow-up is required. 2

Long-Term Prevention

Recommend a high-quality diet rich in fiber (≥22 g/day) from fruits, vegetables, whole grains, and legumes, and low in red meat and sweets. 2, 3 This significantly reduces recurrence risk. 2

Do NOT restrict nuts, corn, popcorn, or small-seeded fruits—these are not associated with increased diverticulitis risk. 2, 3

Follow-Up and Monitoring

Outpatient Follow-Up

Re-evaluate all outpatients within 7 days of diagnosis (earlier if clinical status deteriorates). 2, 3, 4

Instruct patients to return immediately for:

Fever >101°F (38.3°C) 2
Severe uncontrolled pain 2
Persistent vomiting 2
Inability to eat or drink 2
Signs of dehydration 2

If symptoms persist beyond 5–7 days despite appropriate management, obtain repeat CT imaging to assess for complications (abscess formation, perforation) rather than simply extending antibiotic duration. 2

Colonoscopy

Perform colonoscopy 6–8 weeks after symptom resolution for:

First episode of uncomplicated diverticulitis (if no recent high-quality colonoscopy) 2, 3
Any complicated diverticulitis (7.9% associated cancer risk) 2
Patients ≥50 years requiring routine screening 2, 3
Presence of alarm features (change in stool caliber, iron-deficiency anemia, rectal bleeding, weight loss) 2

Indications for Drainage or Surgery

Percutaneous Drainage

Perform CT-guided percutaneous drainage for abscesses ≥4–5 cm when feasible. 2, 3, 4 This allows conversion of urgent surgery to elective resection or avoidance of surgery altogether. 2

Surgical Consultation

Obtain surgical consultation for:

Generalized peritonitis or septic shock 2, 3, 4
Failed medical management after 5–7 days of appropriate antibiotics 2
Abscess not amenable to percutaneous drainage 4
Clinical deterioration despite medical therapy 4
Immunocompromised patients with complicated disease 4

Elective Surgery

The decision for elective resection should be individualized based on quality of life impact, frequency of recurrence (≥3 episodes within 2 years), and patient preferences—NOT solely on the number of episodes. 2 The traditional "two-episode rule" is no longer accepted. 2

Elective sigmoidectomy reduces 5-year recurrence from 61% to 15% but carries a 10% short-term and 25% long-term complication rate. 2 The DIRECT trial demonstrated significantly better quality of life at 6 months and 5 years after elective surgery compared with continued conservative management. 2

Prevention of Recurrence

Lifestyle modifications to reduce recurrence risk:

High-fiber diet (≥22 g/day from fruits, vegetables, whole grains, legumes) 2, 3
Regular vigorous physical activity 2, 3
Achieve or maintain BMI 18–25 kg/m² 2, 3
Smoking cessation 2, 3
Avoid nonaspirin NSAIDs when possible (aspirin is acceptable) 2, 3

Do NOT prescribe mesalamine or rifaximin for prevention—high-certainty evidence shows no benefit but increased adverse events. 2

Special Populations

Immunocompromised Patients

Immunocompromised patients require immediate antibiotic therapy (10–14 days), a lower threshold for CT imaging and repeat imaging, and early surgical consultation regardless of other factors. 2, 3, 4 They may present with milder signs despite more severe disease. 2 Corticosteroid use specifically increases the risk of perforation and death. 2

Elderly Patients (>65 Years)

Maintain a lower threshold for antibiotic treatment and closer monitoring in elderly patients, even when outpatient criteria are otherwise met. 2 Age >80 years is an absolute indication for antibiotics. 1, 2, 3

Critical Pitfalls to Avoid

Do NOT prescribe routine antibiotics for uncomplicated diverticulitis without high-risk features—this adds antimicrobial resistance without clinical benefit. 2, 3
Do NOT assume all diverticulitis patients need hospitalization—most immunocompetent patients with uncomplicated disease can be safely managed outpatient. 1, 2
Do NOT discharge patients without CT confirmation of uncomplicated disease. 2, 3
Do NOT apply the "no antibiotics" approach to complicated diverticulitis (Hinchey ≥1b with abscess)—the evidence specifically excluded these patients. 2, 3
Do NOT stop antibiotics early when indicated—complete the full course even if symptoms improve. 2, 3
Do NOT overlook immunocompromised patients—they require immediate antibiotics, lower threshold for imaging, and early surgical consultation. 2, 3, 4
Do NOT unnecessarily restrict nuts, seeds, or popcorn—this is not evidence-based and may reduce overall fiber intake. 2, 3
Do NOT delay surgical consultation in patients with frequent recurrence affecting quality of life. 2

What is the appropriate management of left‑sided diverticulitis, including criteria for outpatient versus inpatient care, antibiotic selection, diet progression, follow‑up, and indications for drainage or surgery?

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