The pathology of diverticular disease.

Diverticular disease is common in the elderly Western population and its complications are frequent clinical presentations. Despite this, the pathogenesis of the condition remains relatively poorly understood. Several theories have been developed, the most acceptable suggesting elastosis of the taeniae coli as the primary event, causing shortening of the sigmoid colon, with relative mucosal excess and subsequent mucosal herniations. A Western-type diet is implicated in the increased uptake of proline from the gut, leading to elastosis of the sigmoid colon. For pathologists, in clinical practice, the disease is most commonly seen in sigmoid colonic resection specimens, usually performed for complications of the disease. It is now realised that mucosal biopsies of the luminal mucosa, in the sigmoid colon affected by diverticular disease, can produce perplexing pathological changes. In particular diverticular colitis can mimic both ulcerative colitis and Crohn's disease: care should be taken when diagnosing chronic inflammatory bowel disease on a background of diverticular disease. For pathologists, diverticular disease remains something of an enigma: although common, its pathogenesis remains ill-defined and its complications can provide diagnostic difficulties, which require precise clinical and radiological correlation.