## Why option 1 is correct The sigmoid colon is the most common site of diverticular disease (~95% of cases in Western populations) because it has the smallest luminal diameter and generates the highest intraluminal pressures according to Laplace's law. This increased pressure, combined with low-fiber diet and chronic constipation, causes mucosa and submucosa to herniate through weak points in the muscular wall at sites of vascular penetration, forming false diverticula (lacking the muscular layer). This pathophysiological mechanism is the fundamental reason why the sigmoid colon is affected in the vast majority of diverticulosis cases (Bailey & Love 28e, Ch 75). ## Why each distractor is wrong - **Option 2**: The rectum does have taeniae coli (three longitudinal muscle bands present throughout the colon), and the rectum is NOT the most common site of diverticular disease; the sigmoid colon proximal to the rectum is affected in ~95% of cases. - **Option 3**: While right colon diverticulosis is more common in Asian populations due to genetic and dietary factors, it is NOT the most common site in the general (Western) population; the sigmoid colon remains the predominant site globally. - **Option 4**: Although vascular penetrations through the muscular wall are indeed weak points where diverticula form, this anatomical feature alone does not explain why the sigmoid is most common—the key is the combination of smallest diameter + highest pressure generation. **High-Yield:** Sigmoid colon diverticulosis (~95%) results from smallest luminal diameter → highest intraluminal pressure (Laplace's law) + herniation at vascular weak points; right colon more common in Asians. [cite: Bailey & Love 28e Ch 75]
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