What is Diverticulosis?
Diverticulosis is the presence of multiple outpouchings (diverticula) of the colonic wall that remain asymptomatic in most individuals, representing an anatomical alteration rather than a disease state. 1, 2
Anatomical Definition
Diverticula are pseudodiverticula—pockets of mucosa bounded by muscularis mucosae and invested with a thin layer of submucosa that herniate through weak points in the muscularis propria, with their tips ending in the colonic subserosa. 3 These weak points occur specifically at sites where nutrient blood vessels (vasa recta) penetrate the muscle layer to supply the colonic mucosa. 4, 3
Epidemiology and Prevalence
The prevalence of diverticulosis increases dramatically with age:
- 32.6% of patients aged 50-59 years have diverticulosis 5
- Over 50% of people over age 60 are affected 4
- 71.4% of patients aged 80 years have diverticulosis 5
Geographic Variation
- Left-sided (sigmoid) diverticulosis predominates in Western populations, affecting approximately 90% of cases 6, 7
- Right-sided (cecal) diverticulosis is dramatically more common in Asian populations, where 70-74% of diverticular disease affects the right colon 6
- Diverticulosis remains uncommon in Africa, with historical prevalence as low as 1.85%, though recent data show increasing prevalence (up to 10.6%) related to adoption of Western dietary patterns 5
Pathophysiology
Diverticula form through herniation of colonic mucosa and submucosa driven by excessive intraluminal pressure at anatomically weak points where blood vessels penetrate the colonic wall. 8
Primary Causative Factors
- Low dietary fiber intake reduces stool bulk and increases propulsive pressures required for defecation 8
- Excessive intraluminal pressure is the fundamental mechanical force driving mucosal herniation 8
- Genetic factors account for 40-50% of diverticular disease risk, with over 30 susceptibility loci identified affecting genes important for connective tissue integrity (PHGR1, FAM155A), smooth muscle function, cell adhesion, and immunity 8
Contributing Risk Factors
- Central obesity increases risk through elevated intra-abdominal pressure 8
- Smoking is an independent risk factor 8
- Medications: NSAIDs, corticosteroids, and opioids increase risk through effects on colonic motility and tissue integrity 8, 1
- Chronic conditions: hypertension and type 2 diabetes are associated with increased risk 1
Clinical Significance
Most individuals with diverticulosis remain asymptomatic throughout their lifetime. 3, 2 The key clinical distinctions are:
- Diverticulosis: Asymptomatic presence of diverticula 7, 1
- Symptomatic uncomplicated diverticular disease (SUDD): Approximately 25% of individuals develop symptoms without complications 2
- Diverticulitis: Only 4-10% of patients with diverticulosis develop acute inflammation during their lifetime 5, 4
Incidence of Diverticulitis
The annual incidence of diverticulitis in the United States is approximately 180 per 100,000 people, resulting in approximately 200,000 hospital admissions annually with healthcare costs exceeding $6.3 billion per year. 5, 1
Diagnostic Approach
Diverticulosis is most commonly an incidental finding on colonoscopy or CT imaging. 4 When diverticulitis is suspected:
- CT imaging with contrast is the gold standard, with sensitivity of 98-99% and specificity of 99-100% 5, 7, 1
- Ultrasound has 90% sensitivity and 90% specificity for acute diverticulitis and is particularly useful in resource-limited settings 5
Important Clinical Distinctions
Diverticulosis vs. Diverticulitis
Diverticulosis itself requires no treatment, as it is simply an anatomical finding. 7 The presence of diverticula does not automatically warrant intervention unless complications develop. 2
Segmental Colitis Associated with Diverticulosis (SCAD)
SCAD is a distinct inflammatory condition affecting colonic segments with diverticulosis, most commonly the sigmoid colon, with both the rectum and proximal colon remaining endoscopically and histologically normal. 5 This represents a separate clinical entity from simple diverticulosis and may show Crohn's-like histologic changes. 5