Bilothorax Following Percutaneous Transhepatic Biliary Drainage for Cholangiocarcinoma: Recognising the Depth of Pleural Reflections.

Percutaneous transhepatic biliary drainage (PTBD) is commonly used to relieve biliary obstruction when endoscopic methods are not suitable. Bilothorax, accumulation of bile in the pleural cavity, is a rare but serious complication of PTBD as the procedure can inadvertently breach the pleura, potentially allowing bile to drain into the pleural cavity. This report describes an 82-year-old woman with cholangiocarcinoma who developed bilothorax following PTBD due to transpleural puncture associated with a kinked biliary catheter. Pleural fluid analysis confirmed bilothorax, and a drain exchange led to clinical and biochemical improvement. The case underscores a critical anatomical consideration: the pleural cavity extends further caudally than the lung margins and may be violated during any percutaneous intervention. Failure to account for the diaphragmatic pleural reflection depth may result in unintended pleural injury and fluid accumulation. Proceduralists must incorporate detailed pre-procedural imaging and anatomical awareness to reduce transpleural complications across a range of percutaneous interventions.