Chapter 20

Short bowel syndrome (SBS) is a disorder of malabsorption resulting from significant small bowel loss secondary to congenital disease or surgical resection. The incidence of SBS is estimated at 1200 per 100,000 live births.1 SBS is the most common cause of intestinal failure. This is defined as a significant reduction in functional small bowel mass, leading to inadequate digestion and absorption, with subsequent growth failure. Other less common causes of intestinal failure include structural enterocyte defects and severe disorders of intestinal motility.2

At birth, the estimated small bowel length is approximately 250 cm for term or near-term infants and approximately 100–120 cm for premature infants <30 weeks gestation. Small bowel length is thought to double in the last trimester of pregnancy. Different systems have been used to describe SBS including those based on etiology, age, and anatomical considerations. In the context of surgical resection, the remaining small bowel length is often used to categorize disease severity. In a short resection, >100–150 cm of small bowel remains, compared to 40–100 cm with a large resection and <40 cm remaining after a massive resection.2

The small bowel has considerable adaptive capacity to compensate for intestinal loss. Intestinal adaptation is defined as a growth process of the remaining small bowel, through morphological and functional changes, leading to improved absorption. This process starts shortly after bowel loss but often continues for months to years. Depending on the segment and length of the lost small bowel, patients with SBS are frequently dependent on parenteral nutrition for prolonged periods of time, sometimes indefinitely. The use of parenteral nutrition has significantly improved the life expectancy of children with SBS. On the other hand, long-term parenteral nutrition can be associated with a variety of complications, some of which can have grave consequences. Patients with SBS who fail medical therapy or develop complications may require surgical interventions, including transplantation. Because of the relatively high mortality, SBS is considered among the most lethal disorders in young children.3

The small bowel is a vital organ involved in digestion, absorption, and fluid balance. The small bowel is divided into three anatomical segments (Figure 20–1). The first is the duodenum, which extends from the pylorus to the duodenojejunal junction, defined by the ligament of Treitz. The proximal half of the remaining small intestine is composed of jejunum and the distal portion is ileum. Some absorption takes place in the duodenum, including that of iron. The main function of the duodenum is to neutralize acidic gastric contents and mix them with intestinal, pancreatic, and hepatic digestive secretions. Absorption mostly takes place in the jejunum and ileum. The jejunum has an abundant surface area enhanced by folds and numerous tall villi. The luminal surface of enterocytes, or intestinal epithelial cells, is in turn covered with finger-like projections termed microvilli, which are collectively referred to as the brush border. Villi become shorter and less abundant in the ileum, which therefore has less absorptive surface area than the jejunum. The center of each villus is occupied by a capillary network that absorbs nutrients which are eventually transported to the liver by the portal venous system. The terminal ileum has a high concentration of lymphoid tissue that assists in immune regulation. The terminal ileum also has site-specific ...

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.

Ok

## Subscription Options

### AccessPediatrics Full Site: One-Year Subscription

Connect to the full suite of AccessPediatrics content and resources including 20+ textbooks such as Rudolph’s Pediatrics and The Pediatric Practice series, high-quality procedural videos, images, and animations, interactive board review, an integrated pediatric drug database, and more.