What causes diverticulitis flares and how are they managed?

What Causes Diverticulitis Flares

Diverticulitis flares are triggered by inflammation of existing colonic diverticula, with specific risk factors including NSAID use, opioid use, corticosteroid use, obesity (BMI ≥30), smoking, physical inactivity, low-fiber diet, and certain genetic variants, though approximately 50% of risk is attributable to genetic factors beyond modifiable control. 1, 2

Primary Triggers and Risk Factors

Medication-Related Triggers

• NSAIDs (non-aspirin) are strongly associated with increased risk of diverticulitis flares and should be avoided when possible 1, 2
• Opioid use significantly increases risk of acute diverticulitis 2
• Corticosteroid use elevates risk of both flares and complications, including perforation 3, 2

Lifestyle and Dietary Factors

• Low-fiber diet increases intraluminal pressure and promotes diverticulitis development 1, 4
• Obesity (BMI ≥30) is an independent risk factor for flares 2
• Physical inactivity increases risk, while vigorous exercise decreases it 1
• Smoking is a modifiable risk factor that should be addressed 1, 2

Important caveat: The traditional belief that nuts, corn, popcorn, and small-seeded fruits trigger flares is not supported by evidence and these foods should not be restricted 1

Medical Comorbidities

• Type 2 diabetes (particularly poorly controlled) increases flare risk 2
• Hypertension is associated with higher incidence 2
• Connective tissue diseases (polycystic kidney disease, Marfan syndrome, Ehlers-Danlos syndrome) predispose to diverticular disease 2
• Immunocompromised states (chemotherapy, organ transplant, high-dose steroids) increase both flare frequency and severity 3, 2

Genetic and Age-Related Factors

• Approximately 50% of diverticulitis risk is genetic, including variants in the TNFSF15 gene 1, 2
• Age >65 years is the strongest demographic risk factor, with prevalence reaching 50-66% in those >80 years 2, 5
• Younger patients (<50 years) who develop diverticulitis tend to have more aggressive disease requiring closer monitoring 6

Prevention of Recurrent Flares

Dietary Modifications

• High-quality diet rich in fiber from fruits, vegetables, whole grains, and legumes (>22.1 g/day protective) 1, 4
• Low intake of red meat and sweets 1
• Fiber supplementation can help but should not replace whole food sources 1

Lifestyle Interventions

• Regular physical activity, particularly vigorous exercise 1
• Achieve or maintain normal BMI 1
• Smoking cessation 1
• Avoid NSAIDs and opioids when alternatives exist 1

Medical Management During Remission

• Some evidence supports intermittent rifaximin (7-10 days monthly) combined with fiber supplementation to reduce recurrence 4
• For patients with chronic post-diverticulitis pain without inflammation, low-dose tricyclic antidepressants may address visceral hypersensitivity 3, 1

Clinical Pearls

Common pitfall: Approximately 45% of patients report ongoing abdominal pain at 1-year follow-up after acute diverticulitis, which is usually due to visceral hypersensitivity rather than ongoing inflammation 3. These patients need reassurance and evaluation with imaging and endoscopy to exclude alternative diagnoses before attributing symptoms to recurrent diverticulitis 3, 1.

Risk stratification: Only 1-4% of patients with diverticulosis will develop acute diverticulitis in their lifetime, but once diverticulitis occurs, the risk of complicated disease is highest with the first presentation rather than recurrent episodes 1, 2.