False Bilothorax Secondary to Incarcerated Left Diaphragmatic Hernia With Intestinal Obstruction: A Case Report and Literature Review.

Bilothorax, or cholethorax, is defined as the presence of bile within the pleural cavity and represents a very rare entity, classically associated with hepatobiliary injuries, trauma, surgery, or subphrenic abscesses. A pleural-to-serum bilirubin ratio greater than 1 is generally considered suggestive of the diagnosis. Most reported cases occur in the right hemithorax due to the anatomical proximity of the liver, whereas left-sided or bilateral cases are exceptional. We report the case of a 39-year-old male with a history of prior penetrating thoracic trauma who presented with abdominal pain, nausea, vomiting, and abdominal distension. Computed tomography revealed intestinal obstruction secondary to a left diaphragmatic hernia. Emergency laparotomy was performed, revealing a herniated and ischemic colon, requiring intestinal resection, a Hartmann procedure, and primary closure of the diaphragmatic defect. In the postoperative period, the patient developed a left pleural effusion. Pleural fluid analysis showed an exudate with neutrophilic predominance, numerous erythrocytes, and a total pleural bilirubin level of 3.0 mg/dL, with a concomitant serum bilirubin of 1.9 mg/dL, resulting in a pleural-to-serum ratio of 1.58. Although the pleural-to-serum bilirubin ratio > 1 meets the classical diagnostic criterion for bilothorax, the clinical presentation, the hemorrhagic appearance of the fluid, and the predominance of indirect bilirubin are more suggestive of a "pseudo-bilothorax" due to intrapleural hemolysis in the context of inflammation and hemorrhage rather than a true biliary effusion. This case highlights the need for cautious interpretation of pleural bilirubin levels in the absence of a clear biliary fistula.