Feasibility, Safety, and Potential Efficacy of Fecal Microbiota Transplantation (FMT) for Gastrointestinal Dysfunction in Children Following Hematopoietic Cell Transplant (HCT).

Inclusion Criteria: * Age \< 22 years old. * Received an allogeneic HCT greater than or equal to 30 days prior to enrollment * Diagnosed with one of the following conditions: 1. Steroid-resistant gut a GvHD (defined as GI symptoms that do not improve within 5 days after initial steroid therapy, \>/= 1mg/kg of prednisolone) OR 2. Steroid-dependent gut a GvHD (defined as the presence of a response to methylprednisolone 2 mg/kg/day but relapsing when an attempt was made to taper steroid treatment). OR 3. Current or prolonged GI dysfunction following HCT, defined as having diarrhea or loose stools \>/= 4 weeks with at least one of the following: 1. Requiring NG or G-tube feeds 2. Requiring TPN or IVF for more than 4 weeks 3. Diagnosis of gastroparesis by GI specialist documented in the medical record * Willing and able to provide informed assent/consent Exclusion Criteria: * Participant is at risk for aspiration pneumonia * History of anaphylactic allergy to foods that are not excluded from the stool donor diet * Female participant who is pregnant or nursing * History of previous FMT * Intra-abdominal surgery within 4 weeks of enrollment * At increased risk for peritonitis: presence of intra-abdominal devices (G-or GJ-tubes are acceptable), receiving peritoneal dialysis, or ascites * Concurrent abdominal radiation therapy * Any acute or chronic illness/condition as well as medication that in the opinion of the investigator puts the subject at greater risk from FMT or may confound the study results.