What causes the double duct sign in the hepatopancreatobiliary system on imaging?
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The double duct sign is caused by simultaneous obstruction of the distal common bile duct and main pancreatic duct, leading to their concurrent dilatation. This radiologic sign is best seen on CT or MRI as two parallel tubular structures.
This finding is most commonly due to malignant lesions such as pancreatic head adenocarcinoma or periampullary tumors. Other etiologies include cholangiocarcinoma, impacted distal bile duct gallstones with associated inflammation, benign strictures, or chronic pancreatitis. Clinically, patients often present with symptoms of biliary obstruction (e.g., jaundice) and/or pancreatic duct obstruction (e.g., abdominal pain, elevated pancreatic enzymes).
Why is it called so?
It is named the double duct sign because imaging demonstrates dilation of two distinct ducts—the common bile duct and the main pancreatic duct—simultaneously, reflecting their anatomical convergence near the ampulla of Vater.
Pathophysiology
The common bile duct and the main pancreatic duct drain through a shared channel at the ampulla of Vater. An obstructing lesion at or near this convergence impairs outflow of both bile and pancreatic secretions, resulting in proximal ductal back-up and dilatation seen as the double duct sign on imaging.
Alternative names: None widely used.
Other associated named signs: None directly associated, but diagnostic adjuncts include signs of pancreatic mass on cross-sectional imaging or classic features of malignant biliary obstruction.
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