Chapter 43

### Key Points

1. Cystic fibrosis (CF) is an autosomal recessive disease characterized by respiratory, digestive, reproductive, and sweat gland abnormalities.

2. Meconium ileus (MI) accounts for up to 33% of neonatal intestinal obstructions and occurs in approximately 20% of newborns diagnosed with CF.

3. More than 1870 distinct mutations of the cystic fibrosis transmembrane regulator (CFTR) protein have been identified, some of which cause CF. The most common mutation is F508del, which accounts for approximately two third of all mutations in patients with CF.

4. Prenatal diagnosis of MI may be made by sonogram, most commonly showing dilated bowel or increased echogenicity within the bowel lumen. The positive predictive value of hyperechoic masses in a high-risk fetus is estimated to be 52%, whereas in the low-risk fetus the estimate is only 6.4%.

5. MI can be simple or complicated. In the simple form, thickened meconium begins to form in utero and, as it obstructs the mid ileum, proximal dilatation, bowel wall thickening, and congestion occur. In complicated MI volvulus, atresia, necrosis, perforation, meconium peritonitis, and pseudocyst formation may occur.

6. Nonoperative management with Gastrografin® enema is the preferred initial treatment option for simple MI. Special care should be observed to avoid hypovolemic shock with adequate prior intravenous (IV) hydration. Bowel perforation may be avoided by forgoing balloon catheter inflation and maintaining a low hydrostatic pressure during enema instillation.

7. Complicated MI and simple MI that fails enema treatment will require bowel resection with a temporary enterostomy or resection with primary anastomosis. The authors advocate a double barrel enterostomy; followed by serial irrigations of the open stomas and enteral feedings in the distal stoma to stimulate bowel growth. Bowel continuity is usually restored 6 to 12 weeks later.

8. Infants with simple MI and CF may be given breast milk or routine infant formula, enzymes, and vitamins. Those who have a complicated surgical course will require either continuous enteral feedings or total parenteral nutrition (TPN). Pancreatic enzymes must be given orally starting at 2000 to 4000 lipase units per 120 mL of full-strength formula.

9. The prognosis for patients with CF and MI is very promising; recently published studies show 1-year survival rates as high as 100%. Long-term follow-up at 13 years shows similar pulmonary function and nutritional status in CF patients with or without MI.

### Introduction

Meconium ileus (MI) is one of the most common causes of intestinal obstruction in the newborn accounting for 9% to 33% of neonatal intestinal obstructions. It is the earliest clinical manifestation of CF, occurring in approximately 20% of patients with CF.

Clinically, CF is characterized by chronic obstruction and infection of the respiratory tract, insufficiency of the exocrine pancreas, and elevated sweat chloride levels. Approximately 10% of patients with CF will remain pancreatic sufficient and tend to have a milder course. Complicated MI often results in prolonged hospital stays at great monetary and emotional cost. In the current era, prenatal diagnosis of MI with ...

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