SHORT BOWEL SYNDROME
Short-bowel syndrome is a disorder clinically defined by malabsorption, diarrhea, steatorrhea, fluid and electrolyte disturbances, and malnutrition. The final common etiologic factor in all causes of short-bowel syndrome is the functional or anatomic loss of extensive segments of small intestine so that its ability to absorb is severely compromised.
Few conditions in pediatric gastroenterology pose as great a challenge as short bowel syndrome (SBS). It represents a complex disorder that affects normal intestinal physiology with nutritional, metabolic, and infectious consequences.
The small intestine is completely formed by 20 weeks’ gestation. Most of its growth prior to birth occurs in the third trimester. Before 27 weeks’ gestation, the average length of the small intestine is 115 cm. This length increases to approximately 250 cm with a diameter of 1.5 cm after 35 weeks’ gestation. In contrast, the adult intestine is 600 to 800 cm in length and 4 cm in diameter. The mucosal surface area increases with age. Infants have 950 square cm; adults have 7500 square cm.
The intestine has an enormous capacity to absorb secretions and ingested fluids. There is extra intestine normally which is why a major loss of the intestine may not result in SBS. Absorption occurs through the lining (mucosa) of the small intestine. Nutrients, vitamin B12, calcium, iron, and bile acids are absorbed through the cells of this lining. Mucus covers the surface of the mucosa cells and acts as a trap to hold nutrients in contact with the cell surface. Mucus also acts as a bacterial barrier.