Diverticulosis is defined as sac‐like protrusions of the colonic mucosa through points of relative weakness where the vasculature penetrates through the bowel wall (Figure 32.1). Diverticular disease of the colon is a prevalent disorder routinely diagnosed on colonoscopy (Figure 32.2). The prevalence increases with age and is seen in about 50–60% of those over the age of 60 years. The geographic distribution is heterogeneous but a higher proportion is seen in the developed world, with colonoscopy‐based studies showing a prevalence of 50% in western Europe and Australia and 13–25% in Asia. In addition, diverticular disease is seen in the right colon in individuals from Asian countries as opposed to the left colon in the western world.

Diverticular disease is the terminology used to describe asymptomatic diverticulosis, an often incidental finding. Clinical manifestations of diverticulosis include acute uncomplicated diverticulitis (AUD), symptomatic uncomplicated diverticular disease (SUDD), segmental colitis associated with diverticulosis (SCAD), and diverticular bleeding. In addition, complications due to diverticulitis include perforation with free air, abscess formation, and strictures or fistulas into adjacent viscera.

There has been a shift in the perceived natural history of diverticular disease in that the lifetime risk of developing acute diverticulitis is now considered to be much lower at <5% compared to prior estimates. In addition, the risk of developing diverticular bleeding is about 0.21% at 1 year and 9.5% at 10 years (Figure 32.3).

Several factors contribute to the pathogenesis of diverticular disease, including structural and functional changes in the connective tissue, colonic motility with more phasic contractions, and alternations in the enteric nervous system with decreased neural density and increased fibrosis in the myenteric plexus. In addition, risk factors associated with diverticular disease include genetic factors, diet and modifiable lifestyle factors, gut microbiota, smoking, obesity, and medications. In terms of genetic factors, genome‐wide association studies from the United Kingdom Biobank identified 42 loci associated with diverticular disease (Figure 32.4). Importantly, these loci are expressed in vascular and connective tissue cells and play a role in the immune system, extracellular matrix, cell adhesions, and motility. The gut microbiota and specifically dysbiosis have been implicated in the pathogenesis of diverticular disease complications, including SUDD. More importantly, a paradigm shift in the role of diet and lifestyle modifications has been documented. Several studies now have shown that a diet high in fiber, vigorous physical activity, decreased red meat intake, and no smoking history have a lower risk of developing diverticulitis (Figure 32.5).

Diverticulosis is an asymptomatic condition. However, patients with acute diverticulitis commonly present with abdominal pain, nausea, vomiting, and change in bowel habit (Figure 32.6). Fever can also be present. Complications of diverticulitis include perforation (Figure 32.7), abscess (Figure 32.8), stricture, and fistula (Figures 32.9 and 32.10

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