Cholecystoduodenal fistula identified on oral contrast-enhanced ultrasound

We describe a case of a cholecystoduodenal fistula (CDF) diagnosed using oral contrast-enhanced ultrasound (CEUS). CDF is a rare type of biliary-enteric fistulation in which an abnormal communication forms between the gallbladder and duodenum. CDF are usually found in older patients, in the context of chronic cholecystitis, and can be associated with serious consequences. Given the non-specific presentation and limitations of the various imaging modalities, CDF are notoriously difficult to diagnose. CEUS is a recognised technique predominantly deployed for imaging following intravenous administration. Experience of CEUS has expanded into endocavitary use, including in the biliary and gastrointestinal systems. We describe a case of a CDF identified on intracavitary CEUS. This case report demonstrates oral ingestion of a diluted ultrasound contrast agent is a novel and safe mode of administration with stability of the contrast agent and the ability to define fistulation.