This case presents the classic sonographic findings of biliary atresia, including:

1. small gallbladder: gallbladder length less than 19 mm is suggestive of atretic gallbladder

2. triangular cord sign: increased echogenicity along the anterior wall of the portal vein, that represents the fibrous ductal remnant of the extrahepatic bile duct

In an infant presenting with conjugated hyperbilirubinemia, sonographic demonstration of small gallbladder and triangular cord sign makes the diagnosis of biliary atresia almost certain. 

The patient underwent a liver biopsy which showed extrahepatic biliary atresia, and portoenterostomy (Kasai procedure) was performed 4 days later.

Courtesy of Dr.Yair Halpern.