Patient Characteristics: HSCR Only.

aSample ID and site identification: 01—Cedars-Sinai Medical Center, Los Angeles, California; 02- Karolinska Institute, Stockholm, Sweden; 03—Children’s Hospital Los Angeles, Los Angeles, California; 04—Children’s Hospital of Oakland, Oakland, California.# This subject was excluded from analysis because this patient had an ileostomy at the time of stool collection.bLocation of TZ: location of transition zone from normal to aganglionic bowel. RS = rectosigmoid colon; DC = descending colon; TV = transverse colon.cDiet: Diet in the first year of lifedUnk = unknowneAbx: Antibiotics received within the 2 months prior to stool collection for this analysis.* = MetronidazolefProbiotics: LB = lactobacillus sp. and bifidobacterium sp. combined; Lr = Lactobacillus reuteri; LG = Lactobacillus GG.g30-day compl: Complications occurring within 30 days of the pull-through operation. IH = internal hernia requiring surgical intervention requiring intestinal resection and ileostomy creation.hChr. Anomalies: Chromosomal or known genetic mutations. Ts 21 = Trisomy 21Patient Characteristics: HSCR Only.