Contact pH of rectal mucosa in humans and dogs

Summary A technique to measure the pH on the surface of rectal mucosa of humans and dogs is described. The mean value for 121 normal subjects (7.9±0.067) was compared with values for groups of human subjects who had active and inactive ulcerative colitis, adenomatous polyps, or rectal carcinoma, and values for subjects who previously had had colonic resections or polypectomies. Statistically significant abnormal values were obtained in subjects with active chronic ulcerative colitis (6.9±0.175), adenomatous polyps (8.2±0.07), or rectal carcinoma (7.6±0.26) and in those subjects who had colon resection for rectal carcinoma (8.2±0.010). The lowered values for the group with active colitis and the group with rectal carcinoma were considered to be due to tissue damage. We are unable to explain the elevated values for the group with polyps and the group with previously-resected rectal carcinoma. The values in patients who had functional diarrhea or inactive colitis or who previously had had polypectomies were not statistically different from the values obtained in normal subjects. The value of the contact pH of rectal mucosa in dogs was 7.5±0.06.