Overlap: Irritable bowel syndrome, inflammatory bowel disease, and diverticular disease

Diverticular disease and its complications overlap with both irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). Diverticular disease and IBS are common gastrointestinal disorders and share common pathophysiologic factors including visceral hypersensitivity, gastrointestinal motor disturbance, a fiber-depleted diet, and subtle mucosal inflammation. New onset IBS-like symptoms in older patients warrant further investigation including colonoscopy to exclude organic diseases. It can be difficult to differentiate symptomatic diverticular disease from IBS, and fecal calprotectin may help in such cases. Rifaximin treatment improves symptoms of both IBS and diverticular disease. The pathogenesis of diverticulitis and diverticular colitis (or known as segmental colitis associated with diverticular disease) may overlap with that of IBD. Pathologic features of IBD can be observed in both diverticulitis and diverticular colitis. Diverticulitis mimics Crohn's disease in presentation and radiologic findings. A follow-up colonoscopy helps to differentiate diverticulitis from Crohn's disease. Diverticular colitis is an infrequent complication of diverticular disease and is limited to the segment of colon with diverticula. Patients with diverticular colitis usually respond to mesalamine and have a better prognosis than IBD. Further understanding of the overlap of IBS, IBD, and diverticular disease may shed light into new therapeutic interventions.