Numerical distribution of lymphoid nodules in the human sigmoid colon, rectosigmoidal junction, rectum, and anal canal.

There is little information on the numerical distribution of lymphoid nodules (LN) in distal segments of the human large bowel. A novel approach was therefore developed to assess the number of LN in the sigmoid colon, the rectosigmoid segment, the rectum, and the anal canal in humans. The distal large bowel from five cadavers was selected for quantitative study. The number of LN was scored macroscopically from the proximal sigmoid colon to the distal anal canal. A numerical distribution, previously unreported, consisting of two circular bands of LN was observed in each of the five cadavers. One band was located 3 cm proximal from the pectinate line and the other was located at the rectosigmoid segment. Significantly more LN occurred 3-5 cm proximal to the pectinate line compared to areas distal or proximal to this band of LN. This band of LN has not been reported previously in humans.