Parenteral nutrition (PN) is the provision of nutrients via the intravenous route. Parenteral nutrition associated metabolic bone disease (MBD) was first described in children in the 1980s. Since then, there has been little to no research into the underlying relationship and as a result, little evidence on which to base clinical care. In adults, MBD is associated with increased fractures. At the Hospital for Sick children in Toronto, an intestinal failure program has been set up since 2003. This is the only intestinal failure program in Canada and receives country wide referrals. Most of the patients have short bowel syndrome (SBS) and require PN for prolonged periods, or for life. About 90% of these patients have MBD, and some have had bone fractures. An understanding of the etiology of MBD would provide information to guide care, and prevent this condition. Funding for this area of research however is challenging because intestinal failure requiring long term PN is a rare condition, accounting for approximately 200 - 300 children in all of Canada. The goal of this study therefore is to gather pilot data on markers of MBD in children on long term PN, and to compare these markers to age and gender matched control patients who are fed by mouth or feeding tube. The information gathered from this study will help us begin to understand what is actually happening in the bones of children on long term PN and will form the basis for future studies and improved clinical care.