Short bowel syndrome

Overview
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 does usually not develop unless a person has lost more than two thirds of their small intestine.

Signs and symptoms
The symptoms of short bowel syndrome can include:
 * Abdominal pain
 * Diarrhea and steatorrhea (oily or sticky stool, which can be particularly foul-odored)
 * Fluid retention
 * 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, a now uncommonly performed surgical procedure
 * 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 (20 feet). Short bowel syndrome usually develops when there is less than 1.8 meters (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

Treatments
Symptoms of short bowel syndrome are usually addressed by prescription medicine. These include:
 * Anti-diarrheal medicine (e.g. loperamide, codeine)
 * Vitamin and mineral supplements
 * 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 organ transplant.
 * Parenteral nutrition (PN or TPN - nutrition administered via intravenous line).
 * Nutrition administered via gastronomy tube

Prognosis
There is no cure for short bowel syndrome. In newborn infants, the 4-year survival rate on parenteral nutrition is approximately 70%. 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.

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). There is controversy over the efficacy of these procedures. They are usually performed by pediatric surgeons at quaternary hospital who specialize in small bowel surgery.