Measurement of Body Composition by Air Displacement Plethysmography in Pediatric Intestinal Failure Patients

Inclusion Criteria: * Patients evaluated in the CAIR Program at Boston Children's Hospital will be eligible for participation if they meet the definition of short bowel syndrome and are under 18 years of age. Short bowel syndrome will be defined as a malabsorptive state resulting from congenital or acquired gastrointestinal disease leading to current dependence on parenteral nutrition for greater than or equal to 90 days. If the patient is on intravenous fluids, they must have a stable intravenous fluid regimen for at least 4 weeks prior to the study visit. Exclusion Criteria: * age \< 2 years or ≥ 18 years * presence of cardiac pacing device (BIA may theoretically interfere with pacer functioning) * presence of any other electrical device that might interfere with the BIA such as implantable drug delivery pumps, vagal nerve stimulator and invasive cerebral perfusion monitor * subjects will be excluded due to pregnancy * subjects with ongoing fluid imbalance, clinically evident shifts in fluid compartments (e.g. edema, ascites) or with fluid resuscitation (defined as daily fluid intake more than 150% of maintenance or fluid boluses more than 20 ml/kg/day). Determination of fluid imbalance will be made by the physicians directly involved in the patient's care.