What is the primary muscle abnormality in diverticular disease?
The longitudinal muscle layer of the colon is primarily divided into three bands, termed the taeniae coli . In diverticular disease, elastin deposits between normal muscle fibers in the taeniae coli. Macroscopically, the taeniae coli are shortened and thickened, resulting in overall shortening and straightening of the colon and redundancy of the circular muscle fibers and mucosa. The circular muscle forms thick, 180-degree bands of muscle that cross the colon. This “bunching” together of the circular muscle layer and the mucosa of the colon occurs particularly in the sigmoid colon. The muscle abnormality is termed myochosis . The longitudinal muscle abnormality has also been termed circular muscle thickening , hypertrophy , or bunching . The term diverticular disease implies circular muscle bunching ( Figure 26-17 ). The term diverticulosis implies presence of diverticula with or without circular muscle bunching.