Neonatal short bowel syndrome (SBS) is a diagnosis with three major elements. The neonate has a shortened small intestine, either congenital or via surgical resection, has intestinal malabsorption to a degree that standard feeding practices cannot support normal growth, and requires intravenous nutrition (IVN) support for a “significant” period. Some authors state that the diagnostic criterion for neonatal short bowel syndrome is the loss of 50% of the small intestine. Several factors make this definition inappropriate. Intestinal resection in the neonate is usually a surgical emergency. In this setting, measurements of the resected and remaining intestine may not be made or may be inaccurate because of bowel necrosis, edema, and adhesions. Factors other than the length of residual bowel also have an impact on the neonate's subsequent dependence on IVN. The anatomic area of bowel resected, the presence or absence of the ileocecal valve and colon, the viability of the remaining intestine and associated medical and surgical problems all have an impact on intestinal absorptive function that might produce intestinal insufficiency even after a modest resection.

The causes of neonatal short bowel syndrome are fairly predictable but the relative frequency depends upon the patient population of the individual center providing the statistics (Table 34.1). Most series of neonates and infants report four major causes – neonatal necrotizing enterocolitis (NEC), mid-gut volvulus, intestinal atresias, and gastroschisis. In most nurseries, NEC accounts for about 50% of all cases of neonatal SBS, with volvulus, atresia, and gastroschisis accounting together for about 40%.