<p><strong>OBJECTIVES: </strong>The objective of this study was to characterize gut microbiome profiles of infants with congenital hyperinsulinism (HI) who underwent near-total or partial pancreatectomy for hypoglycemia management, as compared with healthy controls.</p>

<p><strong>METHODS: </strong>A prospective observational cohort study was performed. Subjects were infants (0-6 months) with HI who underwent removal of pancreatic tissue for management of intractable hypoglycemia from February 2017 to February 2018 at the Children's Hospital of Philadelphia. Fecal samples were collected postoperatively, on full enteral nutrition. The gut microbiome of HI subjects was analyzed and compared with age-matched samples from healthy infants.</p>

<p><strong>RESULTS: </strong>Seven subjects with ≥50% pancreatectomy and 6 with &lt;50% pancreatectomy were included. α (within-sample) diversity was lowest among infants with ≥50% pancreatectomy (richness: false discovery rate, 0.003; Shannon index: false discovery rate, 0.01). β (between-sample) diversity (Bray-Curtis dissimilarity, P = 0.02; Jaccard distance, P = 0.001) differed across groups (≥ or &lt;50% pancreatectomy, controls). Bifidobacteria and Klebsiella species were least abundant among infants with ≥50% pancreatectomy but did not differ between infants with &lt;50% pancreatectomy and historical controls.</p>

<p><strong>CONCLUSIONS: </strong>Infants with HI who underwent ≥50% pancreatectomy differed from age-matched infants in gut microbiome profile, whereas those with &lt;50% pancreatectomy more closely resembled control profiles. The durability of this difference should be investigated.</p>