Measurement of Jejunal Surface pH in Situ by Plastic pH Electrode in Patients with Coeliac Disease

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Abstract
Attaching plastic pH electrodes to a Crosby capsule provides a means of measuring mucosal surface pH in the small intestine during jejunal biopsy. Plastic electrodes, with operating characteristics comparable to glass electrodes within the physiological pH range, were selected because of their mechanical flexibility. The sensing tip can be placed close to the capsule aperture to facilitate contact with the intestinal mucosa. Using this system, the jejunal mucosal surface pH was found to be 5.97 ± 0.07 in 15 control subjects. In contrast, 13 coeliac patients had a significantly (p < 0.001) higher jejunal surface pH of 6.73 ± 0.15, subdivisible into 4 untreated patients with a mean value of 6.95 ± 0.33 and 9 patients on a gluten-free diet with a mean value of 6.63 ± 0.15, both higher (p < 0.01, p < 0.005) than the control value. An elevated jejunal surface pH in coeliac disease was associated with partial or subtotal villous atrophy and with low brush border enzyme activities. Confirming previous in vitro findings, the elevated surface pH in coeliac jejunum may affect digestive and absorptive processes occurring at the brush border.