Background and study aims: Computed tomography colonography (CTC) is an accurate tool for assessing the large intestinal anatomy. Our aims were to determine the normal distribution of in vivo colorectal anatomy and to investigate the effect of age, sex, and body mass index (BMI) on colorectal length. Patients and methods: Asymptomatic adults who underwent primary CTC examination at a single institution over an 8-month period were evaluated. The interactive three-dimensional map was used to determine total and segmental lengths and number of acute-angle flexures. The two-dimensional multiplanar display was used to measure luminal diameters. The effects of age, sex, and BMI on colorectal lengths were examined. Results: The study cohort consisted of 505 consecutive adults (266 women, mean age 56.6 years). Mean total colorectal length was 189.5±26.3cm and mean number of acute-angle flexures was 10.9±2.4. Total length for older adults (>60 years) did not significantly differ from those who were younger than 60 years (P=0.22), although the transverse colon was significantly longer in older adults (P=0.04). Women had significantly longer colons than men (193.3cm vs. 185.4cm, P=0.002), whereas overweight adults (BMI>25) had significantly shorter colons compared with those with BMI25 (187.2cm vs. 194.5cm, P=0.005). Differences in total length were predominately due to differences in the transverse colon. Conclusions: Our results define the normal distribution of colorectal anatomy in an asymptomatic adult cohort, and may help to facilitate both colonoscopy training efforts and design of novel endoscopic devices. The transverse colon was the major determinant in length differences according to age, sex, and BMI, and was significantly longer in older adults, women, and thinner adults, respectively.
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