Radiological anatomy of the sigmoid colon

The variable incidence of sigmoid volvulus, which depends on the presence of an elongated sigmoid colon, suggests the possibility of variations in the length of the sigmoid colon. This study was undertaken among the three major population groups to prove this hypothesis.

Radiological films of patients of the three population groups (African, Indian and White) undergoing barium enema were reviewed. The stature was measured by the distance from T12 to L4. The collective length of the rectum and sigmoid colon as well as the entire colon was measured on the barium enema film using an opisometer. Measurement was from the upper border of the symphysis pubis to the upper border of the left iliac crest. The level of the apex of the sigmoid colon loop and its redundancy were also assessed.

There were 109 patients (61 females) undergoing barium enema (39 Africans, 49 Indians, and 21 Whites). For the entire group the T12-L4 distance was 16.6 +/- 2.2 cm and the entire colon length was 133 cm (range 88-262 cm) and was significantly longer among African patients (P = 0.003). The combined length of the rectum and sigmoid colon was 48.8 +/- 15.7 cm (Africans 60.9 +/- 14.4 cm, Indians 41.3 +/- 12.2 cm and Whites 44 +/- 11.6 cm). The sigmoid colon was significantly more redundant in Africans (90%), compared to Indians (25%) and Whites (24%) (P = 0.003 for Indians and P = 0.048 for whites). The apex of the sigmoid colon reached L1-L3 in 54% among Africans, 6% among Indians and in 10% among Whites (10%).

African patients had the longest combined length of the rectum and sigmoid colon translating into a long sigmoid colon. They also had the highest number of redundant sigmoid colon. This may explain the high incidence of sigmoid volvulus in African patients.