Ascariasis

1. Pathogenesis:

• Largest intestinal roundworm that is parasitic in humans.
   
• Found in tropical and semitropical countries, thriving in areas with poor sanitation. As recent as fifty years ago, it was common in Virginia.
   
• Most common small bowel parasite.
   
• Larvae mature into adult worms in the alimentary tract.
   
• Possible complications: intestinal obstruction, peritonitis, appendicitis, and hemoptysis.
   
• May migrate into the common bile duct and cause signs and symptoms of biliary obstruction.

2. Radiographic findings:

• Single worm may produce intraluminal filling defect within opacified bile duct.
   
• Long worms in intestine may appear as elongated radiolucent filling defects.
   
• Figures: Ascariasis in bile duct of twenty-eight y.o. Vietnamese male with elevated Liver Function Test (LFT). Contrast agent injected into bile ducts during ERCP outlines single linear defect in extrahepatic duct.

              

  
  
• Figure: Endoscopic views of worm backing out of bile duct into duodenum.