Density of lymphoid follicles in the rectum and at the anorectal junction.

To determine the density of mucosal lymphoid follicles in 10 histologically normal rectums, including the anorectal junction, we counted the follicles macroscopically after the specimens were fixed in 10% acetic acid. The mean density in the rectum was 25.6/cm2. The mean density at the anorectal junction was slightly but not significantly higher, at 29.2/cm2. We found no significant change in follicle density with increasing age in specimens from people between the ages of 17 and 90 years.