DISCUSSION

F. hepatica is a zoonotic trematode that infects sheep, goats, and cattle as normal hosts. Humans acquire the parasite after ingestion of aquatic plants, such as watercress, that are infested with metacercariae, drinking contaminated water, or eating the uncooked liver of infested animals [1]. Human fascioliasis has two stages: the acute hepatic stage and the chronic biliary stage. The infected metacercariae excyst in the small bowel, penetrate the intestinal wall, migrate to the liver, and penetrate the liver capsule and hepatic parenchyma to the bile duct. The flukes then reside within the bile ducts. In its chronic biliary phase, F. hepatica infestation results in periodic bile duct obstruction, inducing obstructive jaundice, cholangitis, and/or acute biliary pancreatitis [1,6,9,10]. A diagnosis of human fascioliasis is usually achieved by detecting eggs in the stool or a serological test for antibodies against the worm. However, these diagnostic approaches may not be practical without suspicion for fascioliasis; especially in non-endemic areas [1,2].

In non-endemic areas, diagnostic evaluation in patients with acute cholangitis and biliary pancreatitis is typically performed from the perspective of choledocholithiasis or biliary malignancy, which are more common diseases. Indeed, vague findings of bile duct obstruction by F. hepatica may lead to a clinical misdiagnosis of cholangiocarcinoma in imaging studies, including computed tomography and/or MRCP [11-13]. For human fascioliasis, ERCP should be performed to evaluate and treat bile duct obstruction that allows the detection and extraction of the motile leaf-like worm [3,4,7]. In previous reports, ERCP had a key role in the diagnosis and treatment of biliary fascioliasis. However, a cholangiogram did not reveal the cause of the cholangitis in this case. The leaf-like structure of F. hepatica enables its attachment to the bile duct wall, and can be overlooked on a cholangiogram. IDUS is readily performed without a sphincterotomy during ERCP and is a very sensitive imaging modality for the bile duct. It is also useful for the differential diagnosis of obstructive jaundice in patients with negative cholangiogram findings. Kim et al. [14] reported the use of IDUS in patients with highly suspected choledocholithiasis but normal ERCP findings. IDUS can detect occult small stones and sludges that would otherwise not be revealed in imaging studies, including ERCP. We performed IDUS to investigate the cause of bile duct obstruction and detected a motile tubular structure. Even in the IDUS evaluation, the leaf-like worm attached to the bile duct was confused as thickening of the bile duct wall. However, another advantage of IDUS is the provision real-time images, and the live motile worm was detected using IDUS. EUS can also be a sensitive imaging modality for the extrahepatic bile duct in real-time, and may be useful for the diagnosis of biliary fascioliasis [8]. However, EUS may be limited for evaluation of the proximal or intrahepatic bile duct. In this case, IDUS revealed the worm in the proximal bile duct. The detected biliary fascioliasis could therefore be treated during the same endoscopic session without endoscope exchange because IDUS is performed adjunctively during ERCP.

In conclusion, F. hepatica induced acute cholangitis in this case. However, it was not detected in imaging studies, including a cholangiogram. Wire-guided IDUS revealed an actively moving worm in the bile duct. IDUS findings of F. hepatica in the bile duct have not been reported previously. Thus, we present this apparently unique case of human fascioliasis diagnosed using IDUS.