GASTROINTESTINAL MANIFESTATIONS IN CYSTIC-FIBROSIS

CFTR, or cystic fibrosis transmembrane conductance regulator, the gene product that is defective in cystic fibrosis, is present in the apica l membrane of the epithelial cells from the stomach to the colon. In t he foregut, the clinical manifestations are not directly related to th e primary defect of the CFTR chloride channel. The most troublesome co mplaints and symptoms originate from the oesophagus as peptic oesophag itis or oesophageal varices. In the small intestinal wall, the clinica l expression of CF depends largely on the decreased secretion of fluid and chloride ions, the increased permeability of the paracellular spa ce between adjacent enterocytes and the sticky mucous cover over the e nterocytes. As a rule, the brush border enzyme activities are normal a nd there is some enhanced active transport as shown for glucose and al anine. The results of continuous enteral feeding of CF patients clearl y show that the small intestinal mucosa, in the daily situation, is no t functioning at maximal capacity. Although CFTR expression in the col on is lower, the large intestine may be the site of several serious co mplications such as rectal prolapse, meconium ileus equivalent, intuss usception, volvulus and silent appendicitis. In recent years colonic s trictures, after the use of high-dose pancreatic enzymes, are being in creasingly reported; the condition has recently been called CF fibrosi ng colonopathy. The CF gastrointestinal content itself differs mainly from the normal condition by the lower acidity in the foregut and the accretion of mucins and proteins, eventually resulting in intestinal o bstruction, in the ileum and colon. Better understanding of the CF gas trointestinal phenotype may contribute to improvement of the overall w ellbeing of these patients.