Idiopathic bile acid malabsorption: long-term outcome

Idiopathic bile acid malabsorption (IBAM) is a rare cause of diarrhoea. The natural history of this disorder has not previously been reported. The aim of our study was to determine the long-term outcome in a cohort of patients with severe IBAM using a subjective assessment and by measuring the proportion of 75Se-homocholic acid taurine (75SeHCAT) retained 7 days after its ingestion.

Twenty-three patients with IBAM were identified in 1989. All had responded well to treatment with a bile acid chelator (cholestyramine or aluminium hydroxide). Questionnaires relating to current clinical symptoms and prescriptions were sent to these patients and their general practitioners. 75SeHCAT tests were performed for objective assessment.

Three patients were lost to follow-up, three had died owing to malignancy and three had been diagnosed as suffering from inflammatory bowel disease. The mean period of follow-up for the remaining fourteen patients was 99.2 (range 48-140) months. Seven of the patients showed an improvement in symptoms and no longer required treatment with cholestyramine. In the remaining seven symptomatic patients, diarrhoea was well controlled by continued treatment with cholestyramine (five patients) or standard anti-diarrhoeal treatment (two patients). All seven symptomatic patients and three asymptomatic patients underwent repeat 7 day 75SeHCAT tests. The test results in the asymptomatic group had all improved so that the retention of the tracer after 7 days was above 5%; all but two patients in the symptomatic group still had values under 5%. However, the small number of patients in both groups precluded statistical analysis.

IBAM is a rare cause of diarrhoea and should be diagnosed only after malignancy and inflammatory bowel disease have been excluded by rigorous investigations. Patients should be followed up as some develop other serious gastrointestinal diseases. Fifty per cent of the patients in our survey have remitted spontaneously and no longer require medication with bile acid chelators or anti-diarrhoeal agents.