Cystic Transformation of Bile Ducts in Children: Todani Classification by Ultrasound
Todani Classification on Ultrasound
According to Hagen-Ansert (2023) and Kamaya et al. (2022), choledochal cysts are classified into five types:
| Type | Characteristics |
|---|---|
| Type I | Fusiform dilatation of the common bile duct; choledochal diverticulum is also classified as Type I |
| Type II | True diverticular outpouching of the bile ducts |
| Type III (Choledochocele) | Dilatation of the distal intramural portion of the CBD with prolapse into the lumen of the duodenum |
| Type IV | Multifocal dilatation of intra- and extrahepatic ducts |
| Type V | Caroli disease |
Type VI is separately identified as isolated cystic dilatation of the cystic duct (extremely rare, not yet included in the classification) (Kamaya et al., 2022).
Ultrasound Findings
Choledochal cysts are visualized as true cysts in the right upper quadrant (Hagen-Ansert, 2023). The lesion represents cystic dilatation of the biliary system. Cysts may be associated with cholelithiasis, pancreatitis, or cirrhosis.
Etiology and Clinical Presentation
Most cases are considered congenital and are associated with bile reflux (Hagen-Ansert, 2023). Patients present with complaints of a palpable abdominal mass, pain, fever, or jaundice. The diagnosis may be confirmed by hepatobiliary scintigraphy.
Anomalous Pancreaticobiliary Union (APBDU)
Congenital choledochal cysts include a spectrum of anomalies of Todani types I and IV; in 90% of cases there is APBDU, which is associated with the highest risk of malignant transformation (Kamaya et al., 2022). APBDU classification according to Komi: Type I union (Todani B-P) — perpendicular insertion of the CBD into the pancreatic duct (right-angled union, cystic dilatation); Type II union (Todani P-B) — perpendicular insertion of the pancreatic duct into the CBD (acute-angled union, fusiform dilatation).
Frequently asked questions
Which Todani type is choledochocele classified as?
Type III — this is dilatation of the distal intramural portion of the common bile duct with prolapse into the duodenum (Hagen-Ansert, 2023).
Which types have the highest risk of malignant transformation?
Congenital choledochal cysts of Todani types I and IV; in 90% of cases they are accompanied by APBDU and have the highest risk of malignant transformation (Kamaya et al., 2022).
What does a choledochal cyst look like on ultrasound?
Like a true cyst in the right upper quadrant — cystic dilatation of the biliary system (Hagen-Ansert, 2023).
What is classified as Type V according to Todani?
Caroli disease (Hagen-Ansert, 2023; Kamaya et al., 2022).
What test can confirm the diagnosis of choledochal cyst?
The diagnosis may be confirmed by hepatobiliary scintigraphy (nuclear medicine hepatobiliary scan) (Hagen-Ansert, 2023).