We present the real-time sonographic features of 19 surgically proven
cases of hepatobiliary ascariasis, in which ultrasound examination was
the primary modality used to achieve the diagnosis. All the patients
presented with right upper quadrant abdominal symptoms. There were no
false positive diagnoses. The ''impacted worm'' sign, reported here fo
r the first time, presented in two patients as long curved, tubular, n
on-shadowing structures with echoluscent cores, in the distribution of
the intrahepatic biliary ducts. Both of these patients died soon afte
r surgery indicating poor prognosis in such cases. Two other patients
are described in whom macerated round worms were seen as intraluminal,
localized, soft tissue masses in the common duct mimicking a cholangi
ocarcinoma. Thus, biliary ascariasis must be added to the differential
diagnosis of an intraluminal bile duct mass in patients from endemic
areas. (C) 1996 John Wiley & Sons, Inc.