Part 1: This part will not include any stable isotopes. We will collect the ostomy and urine output for 24 hours to determine the zinc and copper content of the ostomy output and the urine. A small collection of blood (2 mL) will also be obtained at the same time other routine blood tests are being done. This blood will be tested for zinc, copper, and ceruloplasmin levels. If the infant has a replogle or other gastric tube, gastric residuals will be collected during the same 24 hours that stool from the ostomy is collected. If for some reason Part 1 is not able to be performed before the subject meets the criteria for Part 2, the subject will not be dropped. Part 1 will be considered optional. The following will be measured: zinc intake (from the zinc content of the TPN), endogenous fecal excretion (from the ostomy and gastric outputs) and urinary zinc excretion (from the urine collection). Zinc balance will be estimated from the difference in zinc intake and zinc output (in the ostomy, urine, and gastric fluid). Copper balance will be measured from the difference in copper intake (in TPN) and copper losses (in the ostomy, urine and gastric fluid).