Rectal potential difference and histology in Crohn's disease

Prospective study of morphologic and functional changes with time in the mucosa of the ileoanal pouch: functional appraisal using transmucosal potential differences

PURPOSE

This study was undertaken to investigate the morphologic and functional changes with time in the mucosa of the ileoanal pouch.

METHODS

A morphologic study by histopathologic analysis, mucosal morphometry, and mucin histochemistry and a functional study by analysis of transmucosal potential difference were performed in 27 patients with an ileoanal J-pouch after restorative proctocolectomy for ulcerative colitis. In 19 patients with a normal ileoanal pouch, two prospective follow-up analyses were performed after median functional pouch times of 14 and 39 months. We also evaluated eight patients with the diagnosis of pouchitis (median follow-up, 52.5 months).

RESULTS

In the normal ileoanal pouch group, some degree of chronic and acute inflammatory infiltration was identified in 100 percent and 63.2 percent of cases, respectively, with no significant differences being observed between the two follow-up analyses. The mean villous atrophy index at the first and second follow-up was 0.54 and 0.52, respectively, significantly lower (P < 0.001; an indication of a greater degree of villous atrophy) than the value obtained from the control group with a healthy terminal ileum (0.77). The group of patients with pouchitis exhibited statistically significant differences in the degree of acute and chronic inflammatory infiltration, the extent of ulceration, the crypt depth, and the villous atrophy index, compared with patients without pouchitis. In the normal ileoanal pouch group, the median percentage of sulfomucin with each degree of atrophy (1=mild; 2=moderate; and 3=severe) was 2.6, 4.5, and 20.9 percent, respectively. In patients with pouchitis, the median percentage of sulfomucin was 5.9 percent. The mean transmucosal potential difference at the first follow-up (-25.3 mV) was significantly lower (P=0.001) than at the second (-30.4 mV). Significant differences were apparent with respect to both the normal ileum (-8.9 mV) and the normal rectum (-40.2 mV).

CONCLUSION

These results suggest that the ileal pouch behaves as a neorectum, with different degrees of colonic metaplasia from a morphologic and a functional perspective.

The effect of cathartic agents on transmucosal electrical potential difference in the human rectum

Active ion transport in the colon is generating a transmucosal electrical potential difference (PD) of about 40 mV. Cathartic agents inhibit electrolyte and water net-absorption or cause net-secretion which should be reflected in a change of PD. In 83 normal subjects the effect of an isotonic eletrolyte solution (control) and different cathartic agents on rectal PD was tested: Laxatives (bisacodyl, rhein), bile acids (cholic and deoxycholic acid), fatty acids (oleic and ricinoleic acid) and cardiac glycosides (meproscillarin, digitoxin, digoxin). Bisacodyl, deoxycholic acid in high concentration, meproscillarin and digitoxin significantly decreased PD, while the other substances did not. Cathartics act on different transport mechanisms which together with different absorption characteristics of the proximal and distal colon may explain the difference in effecting the PD. Rectal PD measurement provides an easy and convenient tool to document effects of cathartic agents on electrolyte transport, otherwise difficult to obtain, and is applicable for clinical use.

Clinical features and natural history of Crohn's disease

Records of 1084 patients entered into the National Cooperative Crohn's Disease Study were analyzed to gather information concerning the natural history and clinical features of Crohn's disease. The age of onset reached a single peak between the second and fourth decade and was evenly distributed in both sexes. There was an average interval of 35 mo from onset of symptoms to diagnosis. Involvement of both colon and terminal ileum was the most frequent pattern and was present in 55% of patients. The disease was confined to the terminal ileum, other areas of the small intestine, or colon-only in 14%, 3%, and 15% of patients, respectively. Sigmoidoscopic abnormalities were seen in 34% of all patients and 51% of patients with Crohn's colitis. Diarrhea, abdominal pain, weight loss, and fever were present in the majority of the patients. Lower GI bleeding, fever, and perianal complications characterized patients with colon-only involvement. The frequency of extra intestinal manifestations was similar in all groups. Among patients who were randomized to placebo, 32% achieved a spontaneous remission by the end of 17 wk, and 53% of these were still in remission at the end of 24 mo. Clinical remission was associated with an improvement in barium x-rays in 18% of the patients. The predicted factors associated with favorable outcome in placebo-treated patients were: previous surgical removal of all observable disease, absence of perianal disease, and Crohn's Disease Activity Index value under 200.