Bile acid malabsorption investigated by selenium-75-homocholic acid taurine (75SeHCAT) scans, a retrospective single-centre experience

Background: Bile acid malabsorption (BAM) is a common entity in patients experiencing chronic watery diarrhea. However, literature suggests that BAM is underdiagnosed and undertreated. In many countries 75SeHCAT is the gold standard for diagnosing BAM (1-5). The aim of this retrospective study was to investigate the frequency of BAM using 75SeHCAT scintigraphy and the response to treatment with bile acid sequestrants.

Methods: We retrospectively evaluated the clinical data of 420 patients who had a 75SeHCAT scan from January 2016 to January 2023. Electronic medical records were investigated for risk factors of BAM. BAM was defined as a 75SeHCAT retention of less than 15%. Response to bile acid sequestrants was evaluated based on outpatient clinical reports.

Results: Median age at the time of 75SeHCAT test was 47 years (range 14-87). Out of 420 patients, 192 (46%) had a positive result for BAM. Cholecystectomy and ileal resection were significant predictors for BAM (p<0.001). BAM type 1 is statistically more likely to be more severe compared to type 2 (p<0.0001) and compared to type 3 (p=0.0021). In patients who fulfilled Rome IV criteria for IBS-D or functional diarrhea, 75 out of 121 (38%) tested positive for BAM. Overall, treatment with bile acid binders was effective in 76%.

Conclusions: This retrospective study of patients who underwent SeHCAT scanning confirms that about 1/3 patients presenting with therapy-resistant chronic diarrhea in secondary care suffer from BAM. Including the test in clinical management protocols of chronic diarrhea allows early and quantitative diagnosis and treatment of BAM.

Keywords: bile acid malabsorption, bile acid diarrhea, selenium-75-homocholic acid taurine scan, bile acid sequestrants, cholestyramine.