Short bowel syndrome can be caused by prenatal events, such as volvulus, small bowel atresia, gastroschisis or malformation. Acquired causes of the syndrome include necrotizing enterocolitis, volvulus, meconium ileus, massive trauma to the abdomen and, although rarely in children, Crohn disease (Box 359.1). Because most cases occur in the perinatal period, the remaining bowel must be capable of adapting to provide sufficient absorption of water and electrolytes to maintain homeostasis and nutrients sufficient to sustain growth. Compensatory intestinal growth dominated by villous hyperplasia usually occurs within
3 years after resection. In the more severe cases, various degrees of nutrient malabsorption may persist, rendering it impossible for affected patients to sustain life or growth without additional intravenous nutrition. In addition, poor peristalsis as a result of damaged bowel from the initial insult or from narrowing of intestinal surgical anastomosis or peritoneal fibrosis or both may impair enteral nutrition.

Ultimately, total oral or enteral nutrition may be feasible if at least 20 to 30 cm of small bowel remains and the ileocecal valve is intact. During the adaptation period, and sometimes during periods of accelerated growth, the administration of intravenous nutrition may be mandatory. Some patients may tolerate enteral feedings only when they are administered as a constant infusion through a gastrostomy. The degree of nutrient malabsorption that results from a short bowel is related to the extent of the resection, the topography of the segment of bowel resected, and the existence of the ileocecal valve. Removal of the ileocecal valve complicates the clinical condition because it facilitates bacterial overgrowth. In some cases, however, intestinal peristalsis may be affected, and nutrient absorption can be impaired, even when a reasonable length of bowel remains functional.