Introduction Bile acid diarrhoea (BAD) is a common disorder which in the primary, idiopathic form may result from low serum fibroblast growth factor 19 (FGF19) producing impaired regulation of bile acid synthesis. ⁷⁵Selenium Homocholic Acid Taurate (SeHCAT) 7day retention is used in diagnosis, predicting faecal bile acid loss and correlating with fasting serum FGF19. Several groups have shown that overweight and obesity are associated with BAD and low FGF19. Reduced FXR target gene expression, of which FGF19 is one, is associated with gallstones. We hypothesised that the two conditions might share pathophysiologic mechanisms and commonly coexist.

Method SeHCAT 7 day retention values were collected between 2003–2014 in patients being investigated for chronic diarrhoea. Other conditions known to be associated with BAD such as cholecystectomy or Crohn’s disease were recorded. A subset of these patients had fasting FGF19 measured. Retrospectively, gallbladder imaging was added to database following cross-referencing with the NHS trust’s PACS system. Where multiple investigations had been performed, the test nearest to the date of the SeHCAT test was recorded. Imaging reporting gallbladder polyps without gallstones were excluded from the final analysis.

Results Of 578 SeHCAT values on the database, 303 (52%) were positive with a value <15%. 183 had imaging that reported upon the gallbladder, of which 7 were excluded due to the presence of polyps, leaving 176. Of these 103 (59%) had a positive SeHCAT scan, 47 (27%) had gallstones, 12 (7%) had a cholecystectomy, so 59 (34%) had either gallstones or cholecystectomy. There was no significant difference in the rate of gallstones or cholecystectomy by gender (64% v 72%, p = 0.2), but mean age in the gallstones/cholecystectomy group was higher (50 v 57, p < 0.005). Median SeHCAT for the whole cohort was 11.7%. The median SeHCAT for those with gallstones or cholecystectomy was significantly lower than those without (7.2% v 14%, p < 0.001). With cholecystectomy excluded, the median SeHCAT was still lower for those with gallstones (3.8% v 14%, p < 0.0001). Overall, a SeHCAT value of <15% conferred an increased risk of gallstones or cholecystectomy (OR=2.0, 95% CI 1.04–3.919, p < 0.05) and the presence of primary bile acid diarrhoea was associated with gallstones, although this did not reach statistical significance (OR=1.98, 95% CI 0.65–5.99, p = 0.23). FGF19 was measured in 60 patients with imaging, of whom 15 had gallstones or cholecystectomy. There was no significant difference in the median serum FGF19 between those with gallstones or cholecystectomy and those without (224 v 227 pg/ml, p = 0.7).

Conclusion Bile acid diarrhoea is associated with gallstones, even when adjusted for cholecystectomy which is a known risk factor for BAD. Bile acid diarrhoea and gallstones may share a pathophysiological mechanism.

Disclosure of interest None Declared.