Hemorrhagic pancreatic fluid collections examined by ultrasound

Ultrasound examination of nine patients revealed that the appearance of their hemorrhagic pancreatic fluid collections varied depending on the age of the hemorrhage. Acute hemorrhage was visualized as a well-defined homogeneous mass, while subacute hemorrhage (studied about a week after the bleeding episode) appeared as a mass that contained cystic and solid elements or was septated. Remote hemorrhage, studied several weeks after the acute event, was visualized as a simple cyst. Findings of CT, which were available for correlation in eight patients, revealed that acute hemorrhagic collections had CT numbers between 45 and 65 HU: older collections had CT numbers between 14 and 25 HU. The ultrasonographic evolution of hemorrhagic pancreatic fluid collections followed a pattern similar to that described by in vitro studies, which determined that hemorrhage and clotted blood may appear either echogenic or sonolucent, depending on the age of the hemorrhage and the transducer used. Factors that affect the echogenicity of hemorrhagic collections and the difficulties encountered in recognizing them by ultrasound are discussed.