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Clinical Consequences

Effects on the Digestive system

CF commonly leads to several digestive problems, including:

• Pancreatic insufficiency
• Insufficient intestinal secretions
• Meconium ileus in infants
• Portal hypertension
• CF-related diabetes mellitus (CFRD)

Table adapted from: Beers MH, Porter RS, Jones TV, Kaplan JL, Berkwits M. Cystic Fibrosis. The Merck Manual 2005;1-10.²⁰

Complications of the Digestive System

Let’s review in detail some of the common digestive disorders in patients with CF.

Pancreatic Insufficiency^3,18,20

85% to 90% of patients with CF develop pancreatic insufficiency as a result of mucus obstructing the ducts in the pancreas.

• Pancreatic insufficiency causes a deficiency in pancreatic enzymes needed for the digestion of most nutrients. This results in fat and protein maldigestion, producing a bloated stomach and causing frequent, bulky, greasy, foul-smelling stools.
• Uncorrected maldigestion leads to vitamin deficiency, failure to gain weight, and, ultimately, short stature.
• Although rare, patients with class IV-VI CFTR mutations can develop pancreatitis, which may result in some degree of pancreatic dysfunction.
• The majority of patients with CF who develop pancreatic insufficiency require supplementation of pancreatic enzymes, and some need fat-soluble vitamin supplementation (ie, Vitamins A, D, E, and K) as well.

Intestinal Tract

A small number of patients with CF experience changes in the intestinal tract itself.

• Glands in the duodenum of the small intestine become enlarged due to dilated ducts and mucus-filled cells; there is little, if any, primary change of the small intestinal tract mucosa.

Liver³

The blockage of bile ducts by thick secretions can lead to clinically apparent liver disease in 2% to 4% of patients with CF.

• Almost all patients with liver disease also have pancreatic insufficiency, with no correlation to a specific CF mutation.
• Progressive liver disease may lead to liver scarring or cirrhosis in about 5% of adults with CF, although reasons for this are not well understood.
• Cirrhosis may increase pressure in the veins entering the liver (portal hypertension), leading to enlarged, fragile veins at the lower end of the esophagus (esophageal varices) and profuse bleeding.

Gallbladder¹⁸

Anatomic abnormalities of the gallbladder occur in about one third of patients with CF.

• It is common to find that the gallbladder is small in patients with CF and filled with thick, colorless bile that does not function well. Recall that bile is important for the digestion of fats.
• Clinical abnormalities occurring in 1% to 12% of patients with CF include cholecystitis, or inflammation of the gallbladder, and cholelithiasis, or gallstones.
• Most patients with CF who develop gallbladder abnormalities are asymptomatic.

Meconium Ileus^19,20

Approximately 15% of newborns carrying two defective CFTR genes are born with meconium ileus, which is virtually diagnostic for CF.

• Meconium, the dark green substance that emerges as the newborn’s first stool, is thick and passes more slowly than normal stool. If the meconium is too thick, it blocks the intestine.
• Blockage may lead to perforation of the intestinal wall or a twisted intestine. Meconium may also form plugs in the large intestine or anus, causing a temporary blockage. If surgery is not performed to remove the blockage, the infant could die.
• Infants who have meconium ileus almost always develop other symptoms of CF.

Source^19,20

References:
3. Welsh M. Cystic Fibrosis. In: Goldman L, Ausiello D, eds. Cecil Textbook of Medicine. 22nd ed. Philadelphia: WB Saunders; 2004. p. 1-22.
9. Farrell PM, Kosorok MR, Rock MJ, et al. Early diagnosis of cystic fibrosis through neonatal screening prevents severe malnutrition and improves long-term growth. PEDIATRICS 2001;107:1-13.
18. Yankaskas JR, Marshall BC, Sufian B, Simon RH, Rodman D. Cystic fibrosis adult care: consensus conference report. Chest 2004 January;125(1 Suppl):1S-39S.
19. Beers MH, Fletcher AJ, Jones TV, Porter RS, Berkwits M, Kaplan JL. Cystic Fibrosis. The Merck Manual of Medical Information 2007;(2nd):1-8.
20. Beers MH, Porter RS, Jones TV, Kaplan JL, Berkwits M. Cystic Fibrosis. The Merck Manual 2005;1-10.