Usefulness of Peritoneal Fluid Bilirubin and Fluid‐to‐Serum Bilirubin Ratio to Diagnose Bile Leak in Surgical and Trauma Patients

BACKGROUND AND AIMS: Bile leak is a recognised complication in surgery and trauma patients, often resulting in significant morbidity. While various imaging modalities play an important role in diagnosis, their accessibility and feasibility may be limited in clinical settings. Biochemical analysis of peritoneal or drain fluid bilirubin (FB) and fluid-to-serum bilirubin ratio (FSBR) have been proposed as an adjunct diagnostic tool. However, there is limited research on the use of FB or FSBR to diagnose bile leak as various FSBR cut-offs have been proposed in existing literature. We aim to assess the usefulness of FB and FSBR to diagnose bile leak in surgical and trauma patients. The study was conducted in collaboration with Pathology, Surgical and Trauma departments to comprehensively assess pre-analytical, analytical and clinical aspects. METHODS: We performed a prospective study over a 21-month period (February 2023 to October 2024) at a metropolitan tertiary surgical and trauma centre. Contingency table and receiver operating characteristic area under curve (ROCAUC) analyses were made to assess the usefulness of FB and FSBR. RESULTS: Our study included 84 patients (38 post-operative surgical, 15 trauma and 31 medical control patients). Five patients (four surgical and one trauma) were diagnosed with bile leak based on radiological and clinical criteria. Both FB and FSBR are shown to be reliable markers to diagnose bile leak (ROCAUCs for both FB and FSBR > 0.9), with a FB cut-off of 75 μmol/L providing specificity 93.7% and sensitivity 100%, and a FSBR cut-off of 6.0 providing specificity 98.7% and sensitivity 100%. CONCLUSION: Our study demonstrates both FB and FSBR to be useful to diagnose bile leak in both surgical and trauma patients. Further validation through larger, multicentre studies may enhance the generalisability of these findings and refine the role of FB and FSBR in clinical practice.