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: 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 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 Current or prolonged GI dysfunction following HCT, defined as having diarrhea or loose stools >/= 4 weeks with at least one of the following: Requiring NG or G-tube feeds Requiring TPN or IVF for more than 4 weeks Diagnosis of gastroparesis by GI specialist documented in the medical record Willing and able to provide informed assent/consent Exclusion Criteria: Cytomegalovirus (CMV) or Epstein Barr Virus (EBV) IgG negative at the time of consent 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.