Whole-body 75SeHCAT retention is determined by entero-hepatic bile acid recycling rate.

Aim: It has previously been proposed that entero-hepatic bile acid recycling frequency is a major determinant of whole-body retention (WBR) of SeHCAT. Hepatocyte to terminal ileum accounts for almost the entire cycle. The study aim was to test this hypothesis by comparing WBR with an estimate of speed of transit of bile acids using Tc-HIDA scintigraphy performed on a separate occasion.

Methods: Using an un-collimated gamma camera and patient-to-camera distance of 1.5 m, WBR at 7 days after oral SeHCAT administration was measured in 14 patients with chronic diarrhoea, of whom 10 had previous cholecystectomy. The distance reached within the intestine of Tc-HIDA at 1 h (n = 14) and 2 h (n = 7) following iv injection was graded as follows: grades 1 and 2: small bowel on left and right sides of abdomen, respectively; and grade 3: colon. Relationships between WBR and grade were assessed using Spearman rank correlation.

Results: Interval between studies ranged from 3 to 1219 (median 330) days. Grading correlated with WBR at 1 h (rs = -0.63; P = 0.02) and weakly at 2 h (rs = -0.68; P = 0.09) post-injection of Tc-HIDA. In nine patients in whom Tc-HIDA and SeHCAT scans were performed within 1 year of each other, the correlation remained significant at 1 h (rs = -0.73; P = 0.03). There was no difference in WBR or grading between patients with or without a gall bladder.

Conclusion: Entero-hepatic bile acid recycling frequency is a major determinant of whole-body SeHCAT retention.