Diverticulitis: Etiology and Management for NAC OSCE
Etiology (What Causes It)
Diverticulitis happens when small pouches (diverticula) in your colon wall get inflamed—it's now understood to be primarily an inflammatory process, NOT an infection 1, 2.
Simple Explanation:
- Diverticula formation: Weak spots in the colon wall where blood vessels penetrate allow the inner lining to herniate outward, creating pouches
- Why inflammation occurs: Low-grade inflammation, nerve damage, and gut bacteria imbalance (dysbiosis) trigger the disease 3
- NOT caused by: Nuts, seeds, corn, or popcorn (old myth—ignore this!) 4
Risk Factors to Know:
- Increases risk: Obesity, smoking, NSAIDs, corticosteroids, opiates, heavy alcohol 2, 5
- Protective factors: High-quality diet, normal BMI, physical activity, avoiding smoking 2
- Genetics matter too: Patients should understand they can't control everything 2
Management (How to Treat It)
Step 1: Confirm the Diagnosis
Get a CT scan with IV contrast to confirm diverticulitis, especially on first presentation or if severe 2, 4.
Key clinical features:
- Left lower quadrant pain (most common)
- Fever
- Change in bowel habits
- Elevated WBC or CRP
- Tenderness on exam 2, 6
Pitfall: Don't miss colon cancer—1.9% of diverticulitis cases are actually malignancy 2.
Step 2: Classify as Uncomplicated vs. Complicated
Uncomplicated = localized inflammation only (colon wall thickening, peri-colonic changes)
Complicated = abscess, phlegmon, fistula, obstruction, bleeding, or perforation 1, 2
Red flags for complicated disease:
- Symptoms >5 days
- Vomiting
- Pain score >7
- CRP >140 mg/L
- WBC >13.5 × 10⁹/L
- CT showing pericolic air, fluid collection, or long inflamed segment 1
Step 3: Treatment Based on Classification
For UNCOMPLICATED Diverticulitis (Most Patients):
Treat as outpatient with supportive care ONLY—no antibiotics needed for select patients 1.
"Select patients" who DON'T need antibiotics:
- Immunocompetent
- No systemic inflammatory response/sepsis
- Not medically frail
- Can follow up reliably
- Have social/family support
- Well-appearing, pain controlled, tolerating oral intake 1, 6
Supportive care includes:
- Clear liquid diet during acute phase (advance as tolerated) 2
- Bowel rest
- Hydration
- Pain control
When antibiotics ARE needed (uncomplicated):
- Immunocompromised patients 2
- High-risk features (see red flags above)
- Frailty or severe comorbidities
- Unable to ensure safe outpatient management 4, 6
Typical antibiotic regimen: Ciprofloxacin + metronidazole orally 7
For COMPLICATED Diverticulitis:
Always give antibiotics + surgical consultation 6.
- Hospitalization required
- IV antibiotics
- Bowel rest
- Surgery may be needed for diffuse peritonitis, large abscesses, fistulas, obstruction 7
Step 4: Follow-Up After Acute Episode
Colonoscopy timing:
- Wait 6-8 weeks after symptoms resolve (or longer if symptoms persist) 2
- Always do colonoscopy after: Complicated diverticulitis OR first episode of uncomplicated diverticulitis 2, 4
- Can skip colonoscopy if: High-quality colonoscopy within past year with no concerning findings 2
- Do sooner if: Alarm symptoms (rectal bleeding, weight loss, iron deficiency anemia, change in stool caliber) 2
Why colonoscopy matters: 7.9% of complicated cases and 1.3% of uncomplicated cases are actually colon cancer 2.
Step 5: Prevent Recurrence
Lifestyle modifications to reduce recurrence risk 2, 4:
- High-quality diet (fiber-rich)
- Regular physical activity
- Maintain healthy weight
- Stop smoking
- Avoid heavy alcohol
- Limit NSAIDs (aspirin for cardiac prevention is OK)
- DO NOT avoid nuts, seeds, corn, or popcorn 4
Consider fiber supplementation + rifaximin (7-10 days monthly) for symptomatic patients 7.
Step 6: When to Consider Surgery
Elective surgery discussion should be personalized—NOT based on number of episodes 2, 4.
Consider surgical referral when:
- Recurrent uncomplicated diverticulitis significantly affecting quality of life 4
- Complicated disease (abscess, fistula, obstruction, stricture) 7
- Smoldering diverticulitis (persistent pain + inflammation on CT) 2
Important: Risk of complicated diverticulitis is HIGHEST at first presentation, not with recurrences 2.
Key Pitfalls to Avoid
- Don't automatically give antibiotics for uncomplicated diverticulitis in low-risk patients 1
- Don't tell patients to avoid nuts/seeds—this is outdated 4
- Don't skip colonoscopy after complicated diverticulitis or first uncomplicated episode 2
- Don't recommend surgery based on "2 episodes rule"—individualize based on severity and QOL impact 2, 4
- Don't forget immunocompromised patients ALWAYS need antibiotics 2