SeHCAT study: a useful tool to investigate chronic diarrhoea?

Abstract

Introduction The SeHCAT (tauroselcholic [75 selenium] acid) test is the investigation of choice for patients with suspected bile acid diarrhoea (BAD). NICE guidelines advocate against the routine use of SeHCAT for the diagnosis of BAD in patients with chronic diarrhoea of unknown cause.1 We aimed to evaluate the diagnostic yield of SeHCAT testing in relation to risk factors for BAD and assess the tolerability of cholestyramine as a first-line treatment. Methods Retrospective data was collected from 84 sequential patients who had undergone SeHCAT testing at Russells Hall Hospital between January 2022 and July 2022. Data on patient demographics, comorbidities, referral reason, outcome and treatment were collected from electronic records. BAD was defined as less than 15% retention of SeHCAT after 7 days and classified into three subtypes: type 1 (secondary to ileal disease/resection); type 2 (primary or idiopathic); and type 3 (secondary to other gastrointestinal disorders).2 Results Mean age at the time of SeHCAT scanning was 50.5 years. Male:female ratio was 1:2.5. The most common reason for referral was suspected BAD type 2 which accounted for 50.0% of all scans performed. of the 84 patients, 52.4% were diagnosed with BAD following SeHCAT. The mean bile acid retention score for all patients was 18.0%. of patients referred with suspected BAD type 1 and 3, 76.5% and 75.0% were positive, respectively. In patients referred with suspected BAD type 2, a positive scan was found in 33.0%. Cholestyramine was initiated as the first line treatment in 88.6% of cases with confirmed BAD. 23.1% of those commenced on cholestyramine had subsequently switched to colesevelam. Reasons included lack of availability of cholestyramine (66.7%), poor response (22.2%) and intolerable side effects (11.1%). Conclusions SeHCAT is a useful test to investigate chronic diarrhoea in patients with comorbidities related to the development of BAD types 1 and 3. Although patients without underlying risk factors for BAD represent the majority of referrals, the overall diagnostic yield of SeHCAT testing in this cohort is low. This supports current NICE recommendations against routine SeHCAT use. Furthermore, cholestyramine is generally well tolerated as a first line bile acid sequestrant, with the largest barrier to long term treatment being availability of this medication.