This condition, which accounts for about 30% of cases of intestinal obstruction among neonates, is characterized by the inspissation of thick, tenacious meconium in the bowel. The most common cause is cystic fibrosis; approximately 6% to 20% of infants with cystic fibrosis have meconium ileus. Hyperviscous mucus secreted by abnormal intestinal glands, an abnormal concentrating process in the proximal small intestine, and a deficiency of pancreatic enzymes have been implicated in the pathogenesis. The histologic hallmark is distention of the goblet cells in the intestinal mucosa.