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.