Small Intestinal Bacterial Overgrowth in Fontan Patients with Protein-Losing Enteropathy: Preliminary Results

Objective: Small intestinal bacterial overgrowth (SIBO) is characterized by excessive proliferation of colonic bacterial species in the small bowel. Symptoms related to SIBO are abdominal discomfort, intestinal inflammation, malnutrition, and growth failure, which are also common features of protein-losing enteropathy (PLE) in Fontan patients. The aim of this study was to test Fontan patients with PLE for the presence of SIBO.

Methods: Five Fontan patients with relapsing moderate to severe PLE were scheduled for a glucose hydrogen breath test (GHBT) between June 2013 and October 2014 at our institution. SIBO was diagnosed if a fasting breath hydrogen concentration was ≥ 10 ppm or an increase in hydrogen levels of ≥ 12 ppm above the baseline value was measured after ingestion of glucose.

Results: One patient was not able to drink the glucose solution and was excluded from the study. The remaining 4 patients (median age: 6.3 years, all male) successfully underwent a GHBT. Median hydrogen concentrations at baseline, and 1 hour, and 2 hours after glucose ingestion were 6 ppm (range 3 - 16 ppm), 5 ppm (range 1 - 9 ppm), and 6 ppm (range 5 - 10 ppm), respectively. One patient was diagnosed having SIBO (baseline 16 ppm). Clinical features and albumin levels improved after increasing the daily steroid dose in patients without SIBO. Interestingly, the patient with SIBO did not respond to increasing steroid doses. The patient improved after he was treated with rifaximin, a non-absorbable antibiotic.

Conclusion: SIBO may complicate the course of disease in Fontan patients with overt PLE. We identified an additional mechanism that might contribute to long-term outcome in these patients. Further studies are needed to elucidate the clinical role of SIBO in Fontan patients.