A 53-year-old woman was admitted to our hospital with sudden epigastralgia, back pain, and nausea. Upper gastrointestinal endoscopy showed an Ascaris lumbricoides worm in the duodenal bulb, which was removed with biopsy forceps. The patient's abdominal symptom was reduced, but she once again complained of fever, epigastralgia, and nausea. Laboratory data was suggestive of liver injury, and magnetic nesonance cholangiopancreatography (MRCP) revealed a linear low-signal-intensity area, which is surrounded by the high-signal-intensity bile in the common bile duct. Thus, the diagnosis of biliary ascariasis was confirmed. Longitudinal ultrasonographic scanning of the common bile duct revealed the worm body as a thick echoic strip containing a central aechoic tube ("inner tube" sign). The worm was identified by way of endoscopic retrograde cholangiography and extracted using basket forceps after endoscopic papillary balloon dilatation. In Japan, this is the first report of biliary ascariasis diagnosed by MRCP, which is considered to be an useful and non-invasive method for the diagnosis and follow up of biliary ascariasis. It is suggested that symptomatic treatment, the oral administration of pyrantel pamoate, and the use of various endoscopic interventional procedures may be necessary in patients with biliary ascariasis depending on the patient's general condition and complications.
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