Causes of Diverticulitis
Diverticulitis results from a complex interplay of genetic predisposition (accounting for approximately 50% of risk), dietary factors, lifestyle behaviors, and certain medications—not from mechanical obstruction by food particles as historically believed. 1
Primary Risk Factor Categories
The causes and risk factors for diverticulitis fall into four broad, evidence-based categories:
1. Genetic Factors (40-50% of Risk)
- Genetics play the central role in determining diverticulitis risk, with twin and sibling studies demonstrating that 40-50% of susceptibility is hereditary 1
- Risk is three times higher for siblings of affected patients versus the general population
- Risk is higher in monozygotic twins than dizygotic twins, confirming genetic influence
- Over 30 susceptibility gene loci have been identified through genome-wide association studies, with four genes (PHGR1, FAM155A, CALCB, and S100A10) showing stronger effects specifically for diverticulitis 1
- These genes regulate immunity, cell adhesion, connective tissue integrity, membrane transport, and smooth muscle function 1
2. Dietary Factors
Protective dietary patterns:
- A prudent diet high in fiber from fruits, vegetables, whole grains, and legumes while low in red meat and sweets decreases risk 1
- Vegetarian diets are associated with decreased incident diverticulitis 1
- Important caveat: Fiber supplements are NOT a replacement for a high-quality diet 1
Debunked dietary myths:
- Nuts, corn, and popcorn consumption is NOT associated with increased diverticulitis risk 1, 2
- Consuming fruits with small seeds (strawberries, blueberries) is NOT associated with diverticulitis risk 1
3. Lifestyle Risk Factors
Modifiable behaviors that increase risk:
- Obesity, particularly central obesity 1, 3
- Weight gain 1
- Smoking 1, 2, 3
- Physical inactivity—vigorous physical activity specifically decreases risk 1
- Alcoholism (but not moderate alcohol consumption by itself) 1
4. Medication-Related Causes
High-risk medications:
- NSAIDs (nonsteroidal anti-inflammatory drugs)—the risk is greater for non-aspirin NSAIDs than aspirin 1, 2, 3
- Corticosteroids—associated with diverticulitis, perforation, and death 1
- Opiate analgesics—associated with diverticulitis and perforation 1
- Menopausal hormone therapy—increases risk regardless of dose or duration 1
- Immunosuppressive medications (chemotherapy, organ transplant regimens) 1
Pathophysiologic Mechanism
While the exact mechanism transforming diverticulosis into diverticulitis remains incompletely understood 2, emerging evidence suggests:
- Low-grade chronic inflammation in the colonic mucosa may be the first step 4, 5
- Altered intestinal microecology with changes in bacterial flora (dysbiosis) 4, 5
- Sensory-motor nerve damage 4
- Mucosal redundancy, prolapse, fecal stasis, and localized ischemia in diverticular segments 2
Critical clinical point: The traditional model of fecalith obstruction causing acute inflammation has been largely abandoned in favor of this inflammatory/dysbiotic paradigm 4, 5.
Clinical Implications for Risk Stratification
Immunocompromised patients warrant special attention as they are more likely to present with severe or complicated disease, may have milder initial symptoms despite serious pathology, and carry higher risk for progression to perforation and death 1.