BACKGROUNDConventional methods of radiographic examination are often unsatisfactory for identifying worms in the biliary tract. Ultrasonography is a non-invasive, quick and safe procedure known to have diagnostic accuracy. We studied the ultrasonographic appearances of biliary ascariasis and the role of ultrasonography in diagnosis and management.METHODSIn a prospective 5-year study, a sonographic diagnosis of biliary ascariasis was made on 46 Yemeni patients. The diagnosis was based mainly on sonographic appearances supported by clinical and laboratory results and proved by outcome of either surgical or medical management or spontaneous exit of worms. Follow-up ultrasound was performed for all patients to confirm the diagnosis and to monitor management.RESULTSParasites were present in the dilated main bile duct in 23 patients, in the gallbladder in 12 patients, in the intrahepatic ducts in 6 patients, in the main pancreatic duct in 4 patients and as an intrahepatic abscess in one patient. The characteristic appearance of Ascaris lumbricoides was as single or multiple echogenic non-shadowing linear or curved strips with or without echoic tubular central lines that represent the digestive tracts of the worm. A spaghetti-like appearance was seen in 9 patients and amorphous fragments were seen in 2 patients. Sixteen patients underwent surgery, 20 patients were treated medically (including spontaneous exit of the worm in 7 patients without treatment) and in 10 patients worms were extracted by endoscopic retrograde cholangiopancreatography.CONCLUSIONSFollow-up ultrasound was found to be effective in confirming the diagnosis and monitoring management.