T2 W axial image reveals dilated CBD and intraheptic biliary radicals (IHBR) with multiple hypointense linear structures in CBD suggestive of calcified ascariasis.
The roundworm ascaris lumbricoides is an extremely common cause of biliary pathology in endemic regions. The adult worm infests the small bowel but it has a propensity to migrate up into the common bile duct from where it may enter the gallbladder or the intra-hepatic bile ducts. Biliary colic is common while jaundice, ascending cholangitis and parasitic liver abscesses occurs occasionally.
The biliary ascariasis may be complicated or uncomplicated. In uncomplicated biliary ascariasis the clinical picture merges with that of acute acalculous cholecystitis with low grade fever, upper abdominal colic, associated tenderness, muscle guarding in right upper quadrant with a gall bladder mass. Jaundice, hepatomegaly and marked toxemia are usually absent.
Depending on the pathology, the symptoms may rapidly progress rapidly over hours, as follows:
- Biliary colic: Fever and jaundice are often absent; the worms are usually in the ampullary orifice, and removal results in rapid improvement.
- Acalculous cholecystitis: Pain and tenderness in right upper quadrant are reported. Jaundice may or may not be present. The pain often radiates to the back on the right .
- Ascending cholangitis: The patient is usually critically ill with fever, tachycardia, tachypnea, jaundice, severe pain, and severe right upper quadrant or diffuse abdominal tenderness. The liver is tender and enlarged.
- Pancreatitis: Moderate or severe pain and tenderness in the epigastrium and the left upper quadrant is reported, along with associated vomiting of varying intensity. The pain often radiates to the back on the left .
- Hepatic abscess: Severe pain and tenderness is reported in the right upper quadrant. The liver is tender and enlarged.
USG of the abdomen has been advocated as a quick, safe, noninvasive and relatively inexpensive modality for suspected biliary ascariasis and various appearances of roundworms in the biliary tract and gallbladder have been described. The appearances described are as follows:
1. Inner-tube sign: The roundworm may be seen as a thick echogenic stripe with a central anechoic tube (gastrointestinal tract of the worm) in a gall bladder or CBD
2. Stripe sign: Thin non-shadowing stripe without an inner tube, within the CBD or gall bladder .
3. Spaghetti sign: Overlapping longitudinal interfaces in the main bile duct due to coiling of a single worm or several worms in the CBD.