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.