What are the typical symptoms of an acute diverticulitis flare and the recommended management, including criteria for outpatient versus inpatient care, dietary progression, antibiotic choices, and indications for drainage or surgery?

Diverticulitis Flare: Symptoms and Treatment

Typical Symptoms of Acute Diverticulitis

Acute diverticulitis classically presents with left lower quadrant abdominal pain, but the complete triad of pain, fever, and leukocytosis occurs in only 25% of patients. 1, 2

Common presenting features include:

• Left lower quadrant pain (most consistent symptom) 1, 3
• Abdominal tenderness or distention 1, 4
• Fever and malaise 2, 3
• Nausea and vomiting 3, 4
• Leukocytosis (present in approximately 90% of cases) 1, 4
• Symptoms typically develop over hours to days 2

Laboratory findings that suggest more severe disease:

• C-reactive protein >140 mg/L 1, 4
• White blood cell count >15 × 10⁹ cells/L 1, 4

---

Diagnostic Confirmation

CT abdomen and pelvis with IV contrast is the gold standard diagnostic test, with 98-99% sensitivity and 99-100% specificity. 1, 2, 3 This imaging distinguishes uncomplicated from complicated disease and identifies abscess, perforation, fistula, or obstruction. 1, 2

Initial laboratory workup should include:

• Complete blood count 1, 4
• C-reactive protein 1, 4
• Basic metabolic panel 4
• Urinalysis 2

---

Classification: Uncomplicated vs. Complicated

Uncomplicated diverticulitis is defined as localized colonic inflammation without abscess, perforation, fistula, obstruction, or bleeding—this represents approximately 85-88% of cases. 1, 3, 5

Complicated diverticulitis involves any of these features: abscess, perforation, fistula, stricture, obstruction, or generalized peritonitis. 1, 3, 5

---

Treatment Algorithm for Uncomplicated Diverticulitis

Step 1: Determine if Antibiotics Are Needed

For immunocompetent patients with uncomplicated diverticulitis, observation with supportive care alone (no antibiotics) is the first-line approach. 1, 6, 3 Multiple high-quality randomized trials, including the DIABOLO trial with 528 patients, demonstrate that antibiotics do not accelerate recovery, prevent complications, or reduce recurrence in this population. 1, 7

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

Clinical indicators:

• Persistent fever >100.4°F or chills despite supportive care 1
• Refractory symptoms or vomiting 1, 4
• Inability to maintain oral hydration 1, 4
• Symptom duration >5 days before presentation 1, 2

Laboratory markers:

• C-reactive protein >140 mg/L 1, 4
• White blood cell count >15 × 10⁹/L or rising leukocytosis 1, 4

Imaging findings:

• Fluid collection or abscess on CT 1, 4
• Longer segment of colonic inflammation 1
• Pericolic extraluminal air 1, 2

Patient factors:

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

---

Step 2: Outpatient vs. Inpatient Management

Outpatient management is appropriate when ALL of the following criteria are met:

• CT-confirmed uncomplicated disease 1, 6
• Ability to tolerate oral fluids and medications 1, 6, 4
• Temperature <100.4°F 1, 6
• Pain controlled with acetaminophen alone (pain score <4/10) 1, 6
• No significant comorbidities or frailty 1, 6
• Immunocompetent status 1, 6
• Adequate home and social support 1, 6

Outpatient management yields 35-83% cost savings per episode without compromising safety. 1, 5

Hospitalization is required for:

• Complicated diverticulitis (abscess ≥4-5 cm, perforation, obstruction, fistula) 1, 3
• Inability to tolerate oral intake 1, 2
• Signs of systemic inflammatory response or sepsis 1, 3
• Immunocompromised status 1, 3
• Significant comorbidities or frailty 1, 2

---

Step 3: Supportive Care Protocol (No Antibiotics)

For patients managed without antibiotics:

• Clear liquid diet for 2-3 days during acute phase, then advance as tolerated 1, 6
• Adequate oral hydration 1, 6
• Acetaminophen for pain control (avoid NSAIDs) 1, 6
• Bowel rest initially 1, 6

Mandatory re-evaluation within 7 days (or sooner if symptoms worsen). 1, 6 If unable to advance diet after 3-5 days, immediate follow-up is required. 1

---

Step 4: Antibiotic Regimens (When Indicated)

Outpatient oral therapy (4-7 days for immunocompetent patients):

• First-line: Amoxicillin-clavulanate 875/125 mg twice daily 1, 3
• Alternative: Ciprofloxacin 500 mg twice daily PLUS metronidazole 500 mg three times daily 1, 3

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

• Ceftriaxone PLUS metronidazole 1, 3
• Piperacillin-tazobactam 1, 3
• Amoxicillin-clavulanate 1200 mg IV four times daily 1

Duration of therapy:

• Immunocompetent patients: 4-7 days total 1, 3
• Immunocompromised patients: 10-14 days total 1, 3

---

Treatment of Complicated Diverticulitis

Small abscesses (<4-5 cm):

• IV antibiotics alone for 7 days 1, 5

Large abscesses (≥4-5 cm):

• CT-guided percutaneous drainage PLUS IV antibiotics 1, 4
• Continue antibiotics for 4 days after successful drainage in immunocompetent patients 1

Generalized peritonitis or sepsis:

• Emergent surgical consultation for source control (Hartmann procedure or primary resection with anastomosis) 1, 3
• Immediate broad-spectrum IV antibiotics (piperacillin-tazobactam or ceftriaxone plus metronidazole) 1, 3

---

Follow-Up and Prevention

Colonoscopy should be performed 6-8 weeks after symptom resolution for:

• First episode of uncomplicated diverticulitis (if no recent high-quality colonoscopy) 1, 4
• Any complicated diverticulitis episode (7.9% associated cancer risk) 1
• Patients >50 years requiring routine screening 1, 4

Lifestyle modifications to prevent recurrence:

• High-fiber diet (≥22 g/day from fruits, vegetables, whole grains, legumes) 1, 4
• Low intake of red meat and sweets 1, 4
• Regular vigorous physical activity 1, 4
• Maintain BMI 18-25 kg/m² 1, 4
• Smoking cessation 1, 4
• Avoid NSAIDs when possible 1, 4

Do NOT restrict nuts, corn, popcorn, or small-seeded fruits—these are not associated with increased diverticulitis risk. 1, 4

---

Critical Pitfalls to Avoid

Do not prescribe routine antibiotics for uncomplicated diverticulitis without high-risk features—this contributes to antimicrobial resistance without clinical benefit. 1, 7

Do not assume all patients require hospitalization—most immunocompetent patients with uncomplicated disease can be safely managed outpatient with appropriate follow-up. 1, 5

Do not overlook immunocompromised patients—they require immediate antibiotic therapy (10-14 days), lower threshold for repeat imaging, and early surgical consultation regardless of other factors. 1, 3

Do not stop antibiotics early if indicated—complete the full course even if symptoms improve to prevent recurrence. 1

Do not perform colonoscopy during acute inflammation—delay until 6-8 weeks after resolution to reduce perforation risk. 1, 5