Intestinal Obstruction Syndromes in Cystic Fibrosis: Meconium Ileus, Distal Intestinal Obstruction Syndrome, and Constipation

Meconium ileus at birth, distal intestinal obstruction syndrome (DIOS), and constipation are an interrelated group of intestinal obstruction syndromes with a variable severity of obstruction that occurs in cystic fibrosis patients. Long-term follow-up studies show that today meconium ileus is not a risk factor for impaired nutritional status, pulmonary function, or survival. DIOS and constipation are frequently seen in cystic fibrosis patients, especially later in life; genetic, dietary, and other associations have been explored. Diagnosis of DIOS is based on suggestive symptoms, with a right lower quadrant mass confirmed on abdominal radiography, whereas symptoms of constipation are milder and of longer standing. In DIOS, early aggressive laxative treatment with oral laxatives (polyethylene glycol) or intestinal lavage with balanced osmotic electrolyte solution and rehydration is required, which now makes the need for surgical interventions rare. Constipation can generally be well controlled with polyethylene glycol maintenance treatment

Variation in MSRA Modifies Risk of Neonatal Intestinal Obstruction in Cystic Fibrosis

Meconium ileus (MI), a life-threatening intestinal obstruction due to meconium with abnormal protein content, occurs in approximately 15 percent of neonates with cystic fibrosis (CF). Analysis of twins with CF demonstrates that MI is a highly heritable trait, indicating that genetic modifiers are largely responsible for this complication. Here, we performed regional family-based association analysis of a locus that had previously been linked to MI and found that SNP haplotypes 5′ to and within the MSRA gene were associated with MI (P = 1.99×10−5 to 1.08×10−6; Bonferroni P = 0.057 to 3.1×10−3). The haplotype with the lowest P value showed association with MI in an independent sample of 1,335 unrelated CF patients (OR = 0.72, 95% CI [0.53–0.98], P = 0.04). Intestinal obstruction at the time of weaning was decreased in CF mice with Msra null alleles compared to those with wild-type Msra resulting in significant improvement in survival (P = 1.2×10−4). Similar levels of goblet cell hyperplasia were observed in the ilea of the Cftr−/− and Cftr−/−Msra−/− mice. Modulation of MSRA, an antioxidant shown to preserve the activity of enzymes, may influence proteolysis in the developing intestine of the CF fetus, thereby altering the incidence of obstruction in the newborn period. Identification of MSRA as a modifier of MI provides new insight into the biologic mechanism of neonatal intestinal obstruction caused by loss of CFTR function