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

The study participant is being asked to take part in this clinical trial, a type of research study, because the participant has Gastrointestinal (GI) symptoms following a Hematopoietic Cell Transplant (HCT). Primary Objective * To determine the safety and feasibility of FMT for treating a GvHD of the gut following HCT. * To determine the safety and feasibility of FMT for treating HCT induced gut dysfunction. Secondary Objectives * To assess the potential efficacy of FMT for treating a GvHD of the gut following HCT. * To assess the potential efficacy of FMT for treating HCT induced gut dysfunction.

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: * Patient 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.