SHORT BOWEL SYNDROME

Short bowel syndrome (SBS, also short gut syndrome or simply short gut) is a malabsorption disorder caused by the surgical removal of the small intestine, or rarely due to the complete dysfunction of a large segment of bowel. Most cases are acquired, although some children are born with a congenital short bowel. It usually does not develop unless more than two thirds of the small intestine have been removed.

SIGNS AND SYMPYOMS

The symptoms of short bowel syndrome can include:

• Abdominal pain
• Diarrhea and steatorrhea (oily or sticky stool, which can be malodorous)
• Fluid depletion
• Weight loss and malnutrition
• Fatigue

Patients with short bowel syndrome may have complications caused by malabsorption of vitamins and minerals, such as deficiencies in vitamins A, D, E, K, and B12, calcium, magnesium, iron, folic acid, and zinc. These may appear as anemia, hyperkeratosis (scaling of the skin), easy bruising, muscle spasms, poor blood clotting, and bone pain.

CAUSES

Short bowel syndrome in adults is usually caused by surgery for:

• Crohn's disease, an inflammatory disorder of the digestive tract
• Volvulus, a spontaneous twisting of the small intestine that cuts off the blood supply and leads to tissue death
• Tumors of the small intestine
• Injury or trauma to the small intestine
• Necrotizing enterocolitis (premature newborn)
• Bypass surgery to treat obesity
• Surgery to remove diseases or damaged portion of the small intestine

PATHOPHYSIOLOGY

In healthy adults, the small intestine has an average length of approximately 6 meters (19.7 feet). Short bowel syndrome usually develops when there is less than 2 meters (6.6 feet) of the small intestine left to absorb sufficient nutrients. Short bowel syndrome caused by the surgical removal of a portion of the bowel may be a temporary condition, due to the adaptive property of the small intestine. In a process called intestinal adaptation, physiological changes to the remaining portion of the small intestine occur to increase its absorptive capacity.

These changes include:
In healthy adults, the small intestine has an average length of approximately 6 meters (19.7 feet). Short bowel syndrome usually develops when there is less than 2 meters (6.6 feet) of the small intestine left to absorb sufficient nutrients. Short bowel syndrome caused by the surgical removal of a portion of the bowel may be a temporary condition, due to the adaptive property of the small intestine. In a process called intestinal adaptation, physiological changes to the remaining portion of the small intestine occur to increase its absorptive capacity.

These changes include:

• Enlargement and lengthening of the villi found in the lining
• Increase in the diameter of the small intestine
• Slow down in peristalsis or movement of food through the small intestine
• Enlargement and lengthening of the villi found in the lining
• Increase in the diameter of the small intestine
• Slow down in peristalsis or movement of food through the small intestine

TREATMENT

Symptoms of short bowel syndrome are usually addressed by prescription medicine.

These include:

• Anti-diarrheal medicine (e.g. loperamide, codeine)
• Vitamin, mineral supplements and L-Glutamine powder mixed with water
• H2 blocker and proton pump inhibitors to reduce stomach acid
• Lactase supplement (to improve the bloating and diarrhoea associated with lactose intolerance)
• Surgery, including intestinal lengthening, tapering, and small bowel transplant.
• Parenteral nutrition (PN or TPN for total parenteral nutrition - nutrition administered via intravenous line).
• Nutrition administered via gastrostomy tube

In 2004, the FDA approved a therapy that reduces the frequency and volume of TPN, comprising: NutreStoreTM [L-glutamine for oral solution] and Zorbtive [somatropin (rDNA origin) for injection] together with a specialized oral diet. Byrne, TA, Wilmore DW, Iyer K, et al. Growth hormone, glutamine, and an optimal diet reduces parenteral nutrition in patients with short bowel syndrome. Ann Surg. 2005;242;655-661 Surgical procedures to lengthen dilated bowel include the Bianchi procedure (where the bowel is cut in half and one end is sewn to the other) and a newer procedure called serial transverse enteroplasty (STEP—where the bowel is cut and stapled in a zigzag pattern). Heung Bae Kim, MD, and Tom Jaksic, MD, both of Children's Hospital Boston, devised the STEP procedure in the early 2000s. The procedure lengthens the bowel of children with SBS and may allow children to avoid the need for intestinal transplantation. As of June 2009, Kim and Jaksic have performed 18 STEP procedures. The Bianchi and STEP procedures are usually performed by pediatric surgeons at quaternary hospitals who specialize in small bowel surgery.

PROGNOSIS

There is no cure for short bowel syndrome. In newborn infants, the 4-year survival rate on parenteral nutrition is approximately 70%. In newborn infants with less than 10% of expected intestinal length, 5 year survival is approximately 20%. Some studies suggest that much of the mortality is due to a complication of the TPN, especially chronic liver disease. Much hope is vested in Omegaven, a type of lipid TPN feed, in which recent case reports suggest the risk of liver disease is much lower. Although promising, small intestine transplant has a mixed success rate, with postoperative mortality rate of up to 30%. One-year and 4-year survival rate are 90% and 60%, respectively.

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