Small Intestinal Bacterial Overgrowth and Immunological Disturbances in Fontan- Associated Enteropathy

Background Gastrointestinal complications, including protein-losing enteropathy (PLE) and Fontan-Associated Liver Disease (FALD) are common in the group of patients after Fontan procedure. However, the data concerned the Small Intestinal Bacterial Overgrowth (SIBO) occurrence in this group of patients are lacking. The general aim of this study was to determinate the SIBO occurrence in the group of the patients after Fontan surgery. Moreover, we focused to compare the enteropathy, immunological disturbances and SIBO diagnosis depending on the type of Fontan procedure. Methods This was a cross-sectional observational study (years 2021–2024) including patients after Fontan procedure (study group) and healthy subjects (control group) aged 5–18 years from 2 polish pediatric centers. In all subjects’ laboratory tests including blood counts and biochemical parameters were performed. Additionally, in the study group the immunoglobulin serum concentrations and peripheral lymphocytes subpopulation were examined. Lactulose Hydrogen Breath Test (LHBT) was used to SIBO recognition. Enteropathy was diagnosed based on clinical and laboratory features. Results There were no differences in SIBO occurrence between study and control groups. In the group with PLE (16.2%) immunological deficiencies were found more often than in the group without enteropathy (IgG (72.73% vs. 3.51%; p < 0.00), IgA (36.36% vs. 10.53%; p = 0.04), CD4 (100% vs. 56.14%; p = 0.00), CD19 (45.45% vs. 14.04%; p = 0.02). SIBO was recognized more frequently in the group after intracardiac Fontan (ICF) than extracardiac Fontan (ECF) communication (p = 0.01) but was not associated with immunological disturbances. Conclusions The SIBO occurrence in dependence of the type of Fontan procedure may be due to differences in the gut perfusion between ICF and ECF groups, that require confirmation in future research.