How does cystic fibrosis affect the digestive system?

Children with cystic fibrosis (CF) have an abnormality in how a cell protein works. The protein is called the cystic fibrosis transmembrane regulator (CFTR) functions. CFTR controls the flow of water and certain salts in and out of the body's cells. As the movement of salt and water in and out of cells changes, mucus becomes thickened.

In the digestive system, CF mainly affects the pancreas. The pancreas is an organ that secretes substances that help with digestion and control the body's levels of blood sugar.

The abnormality in CFTR causes the secretions from the pancreas to become thick. The thickened secretions can block the ducts within the pancreas. This blockage then causes a drop in the amount of digestive enzymes the pancreas secretes. Because of this, a child with CF has difficulty absorbing fats, some proteins, and fat-soluble vitamins A, D, E, and K.

The problems with the pancreas can become so severe that some of the hormone cells in the pancreas can be destroyed. This may lead to glucose intolerance and type 1 diabetes. About 35 percent of CF patients develop cystic fibrosis-related diabetes in their 20s, and more than 40 percent develop the disease after age 30.

Because of CF's effects on the digestive system, a child with CF may have these symptoms:

• Frequent, bulky, greasy stools

• Rectal prolapse. A rare condition in which the end part of the bowels comes out of the anus.

• Meconium ileus. An obstruction of the bowel caused by the thick and sticky first bowel movement of a baby.

• Fat in the stools

• Constipation

• Stomach pain

• Poor growth

• Gallstones 

The child may also have bloating, flatulence, abdominal pain, and watery diarrhea caused by an overgrowth of bacteria.

The liver may also be affected. A small number of children may actually develop liver disease. Symptoms of liver disease may include:

• Enlarged liver

• Swollen abdomen

• Yellow color to the skin

• Vomiting of blood