Duodenal pH in cystic fibrosis and its relationship to fat malabsorption.

To investigate the relationship between duodenal pH levels and supplemental pancreatic enzyme function in cystic fibrosis, 18 children with this condition had pH recordings performed from the second and fourth part of the duodenum. Compared to age-matched controls, patients with cystic fibrosis had significantly longer periods below a pH of 4.0 in the postprandial period and significantly less time above pH 5.8. These values correspond to the pH levels at which lipase is irreversibly destroyed (pH 4.0) and enteric coating of enzyme supplements dissolves (pH 5.8). A significant relationship was found between the pH recordings from the fourth part of the duodenum and the degree of residual fat malabsorption while taking enteric-coated enzyme supplements. Four patients with an excessively acidic duodenum and residual fat malabsorption despite high-dose enzyme supplementation were treated with misoprostol (Searle), a known acid-reducing agent. There were significant improvements in both duodenal pH values and fat absorption. We conclude that there is a wide range of duodenal pH values found in patients with cystic fibrosis and that the efficiency with which enzyme supplements work is closely related to these pH levels. Administration of misoprostol to those patients with excessively acidic duodenal pH levels as well as residual malabsorption appears to be of benefit in improving both the excessively acidic pH levels and the fat malabsorption.