What is the recommended workup and treatment for a patient presenting with diverticulitis, considering their medical history and potential underlying conditions such as diabetes, hypertension, or heart disease?

Diverticulitis Workup

Initial Diagnostic Approach

For patients presenting with suspected diverticulitis, obtain a CT scan of the abdomen and pelvis with IV contrast as the gold standard diagnostic test, which has 98-99% sensitivity and 99-100% specificity. 1, 2

When to Image

• Perform CT imaging for first-time presentations to confirm diagnosis and assess for complications 3
• CT is essential when symptoms suggest perforation, abscess formation, or other complications 3
• Imaging may be deferred in patients with typical symptoms, prior documented diverticulitis with similar presentation, and no evidence of complications 1
• However, current practice trends toward greater imaging use due to high misdiagnosis rates (34-68%) based on clinical assessment alone 1

Laboratory Studies

Obtain the following initial workup 4, 5:

• Complete blood count (assess for leukocytosis >15 × 10⁹ cells/L) 1
• C-reactive protein (CRP >140 mg/L indicates high-risk disease) 1, 5
• Basic metabolic panel 4
• Urinalysis 4

Risk Stratification After Diagnosis

Uncomplicated vs Complicated Disease

Uncomplicated diverticulitis is localized inflammation without abscess, perforation, fistula, obstruction, or bleeding 4, 3

Complicated diverticulitis involves any of these features and always requires antibiotics and potentially invasive intervention 1, 3

High-Risk Features Predicting Progression

Identify patients at risk for complicated disease based on 1, 5:

• Clinical factors: Age >80 years, symptoms >5 days, vomiting, pain score ≥8/10, ASA score III or IV
• Laboratory markers: CRP >140 mg/L, WBC >15 × 10⁹ cells/L
• CT findings: Pericolic extraluminal air, fluid collection, or longer segment of inflammation
• Comorbidities: Immunocompromised status (chemotherapy, high-dose steroids, organ transplant), cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes 2

Treatment Algorithm

Uncomplicated Diverticulitis in Immunocompetent Patients

Most immunocompetent patients with mild uncomplicated diverticulitis should be managed with observation, clear liquid diet, and acetaminophen for pain control—antibiotics are NOT routinely necessary. 1, 6, 2

This recommendation is based on high-quality evidence showing antibiotics neither accelerate recovery nor prevent complications or recurrence 1, 6

Outpatient Management Criteria

Patients appropriate for outpatient treatment must meet ALL of the following 1, 6:

• Able to tolerate oral fluids and medications
• Temperature <100.4°F (38°C)
• Pain controlled with acetaminophen alone (pain score <4/10)
• No significant comorbidities or frailty
• Adequate home and social support
• Ability to maintain self-care at pre-illness level

When to Prescribe Antibiotics for Uncomplicated Disease

Reserve antibiotics for patients with ANY of the following high-risk features 1, 6, 2:

Systemic factors:

• Persistent fever or chills despite supportive care
• Increasing leukocytosis
• Elevated inflammatory markers (CRP >140 mg/L, WBC >15 × 10⁹ cells/L)
• Refractory symptoms or vomiting
• Inability to maintain oral hydration

Patient characteristics:

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

Disease characteristics:

• Symptoms lasting >5 days prior to presentation
• CT findings of fluid collection, longer segment of inflammation, or pericolic extraluminal air
• ASA score III or IV

Antibiotic Regimens for Uncomplicated Disease

Outpatient oral therapy (4-7 days) 1, 6, 2:

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

Inpatient IV therapy (transition to oral as soon as tolerated) 1, 6, 2:

• Ceftriaxone PLUS metronidazole
• Piperacillin-tazobactam

Duration 1, 6:

• 4-7 days for immunocompetent patients
• 10-14 days for immunocompromised patients

Complicated Diverticulitis

All patients with complicated diverticulitis require hospitalization, IV antibiotics, and surgical consultation. 1, 3

Abscess Management

Small abscesses (<4-5 cm): IV antibiotics alone for 7 days 1, 6

Large abscesses (≥4-5 cm): Percutaneous CT-guided drainage PLUS IV antibiotics for 4 days after adequate source control 1, 6, 3

Surgical Indications

Emergent surgery is required for 1, 3:

• Generalized peritonitis
• Sepsis or septic shock
• Failed medical management after 5-7 days
• Inability to drain abscess percutaneously

Surgical options include Hartmann procedure or primary resection with anastomosis (with or without diverting ileostomy) 3

Follow-Up and Monitoring

Short-Term Follow-Up

• Re-evaluate within 7 days from diagnosis, or sooner if clinical condition deteriorates 1, 6
• If symptoms persist after 5-7 days of appropriate antibiotic therapy, obtain repeat CT imaging to assess for complications requiring drainage or surgery 6, 7

Colonoscopy Timing

Perform colonoscopy 6-8 weeks after symptom resolution for 1, 6:

• All patients with complicated diverticulitis (7.9% risk of colon cancer)
• First episode of uncomplicated diverticulitis
• Patients >50 years requiring routine screening
• Any patient with alarm symptoms (change in stool caliber, iron deficiency anemia, blood in stool, weight loss)

Defer colonoscopy if a high-quality colonoscopy was performed within the past year with no findings warranting short-interval follow-up 1

Prevention of Recurrence

Lifestyle Modifications

Counsel all patients on the following evidence-based interventions 1, 6, 8:

• High-quality diet: High in fiber (>22.1 g/day) from fruits, vegetables, whole grains, and legumes; low in red meat and sweets
• Regular vigorous physical activity
• Achieve or maintain normal BMI (18-25 kg/m²)
• Smoking cessation
• Avoid nonaspirin NSAIDs and opioids when possible (aspirin is acceptable)

What NOT to Recommend

Do NOT restrict consumption of nuts, corn, popcorn, or small-seeded fruits—these are not associated with increased diverticulitis risk 1, 6, 8

Do NOT prescribe mesalamine or rifaximin for prevention—strong evidence shows no benefit 1, 6, 8

Special Populations

Immunocompromised Patients

These patients require heightened vigilance 1, 6:

• Lower threshold for CT imaging, antibiotic treatment, and surgical consultation
• May present with milder symptoms despite more severe disease
• Require longer antibiotic duration (10-14 days)
• Corticosteroid use specifically increases risk of perforation and death

Elderly Patients (>65 years)

• Require antibiotic therapy even for localized complicated diverticulitis 6
• Higher threshold for outpatient management
• Increased risk of complications and mortality

Common Pitfalls to Avoid

• Overusing antibiotics in uncomplicated diverticulitis without risk factors—contributes to resistance without clinical benefit 1, 6
• Failing to recognize high-risk features that predict progression to complicated disease 1
• Assuming all patients require hospitalization when most can be safely managed outpatient with appropriate follow-up (35-83% cost savings) 1, 6
• Applying the "no antibiotics" approach to Hinchey 1b/2 or higher disease—the evidence specifically excluded these patients 6
• Stopping antibiotics early even if symptoms improve—complete the full course 6
• Delaying surgical consultation in patients with frequent recurrence affecting quality of life 6
• Prescribing unnecessary dietary restrictions (nuts, seeds, popcorn) based on outdated recommendations 1, 8