DOI: 10.1148/radiol.2441041978
(Radiology 2007;244:314-315.)
© RSNA, 2007
The Double Duct Sign1
Jorge Ahualli, MD
1 From the Department of Computed Tomography, Centro Radiológico Luis Méndez Collado, Muñecas 444, San Miguel de Tucumán, Tucumán 4000, Argentina. Received November 21, 2004; revision requested January 1, 2005; revision received January 14; final version accepted February 16.
Address correspondence to the author (e-mail: joahualli{at}sinectis.com.ar).
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APPEARANCE
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The double duct sign is a finding seen at magnetic resonance (MR) cholangiopancreatography (a two-dimensional technique) and consists of simultaneous dilatation of the common bile and pancreatic ducts (Figure) (1,2). This sign can also be seen with other modalities such as endoscopic retrograde cholangiopancreatography (ERCP), computed tomography (CT, especially with curved multiplanar reformations), and ultrasonography (US) (3–5).
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Figure a: Double duct sign in 47-year-old man with ampullary carcinoma. (a) Transverse CT scan without intravenous contrast material enhancement shows dilatation of common bile duct (arrows) and main pancreatic duct (arrowheads). (b) Coronal T2-weighted single-shot Fase MR cholangiopancreatogram (repetition time, 2000; echo time, 250; two-dimensional technique) shows dilatation of the common bile duct (white arrows) and main pancreatic duct (black arrows). The combined dilatation of the common bile and pancreatic ducts create the double duct sign.
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Figure b: Double duct sign in 47-year-old man with ampullary carcinoma. (a) Transverse CT scan without intravenous contrast material enhancement shows dilatation of common bile duct (arrows) and main pancreatic duct (arrowheads). (b) Coronal T2-weighted single-shot Fase MR cholangiopancreatogram (repetition time, 2000; echo time, 250; two-dimensional technique) shows dilatation of the common bile duct (white arrows) and main pancreatic duct (black arrows). The combined dilatation of the common bile and pancreatic ducts create the double duct sign.
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EXPLANATION
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The simultaneous dilatation of the common bile duct (in the intrapancreatic segment) and the pancreatic duct occurs with biductal narrowing (1,2). The narrowing is generally secondary to contiguous obstruction or encasement of the common bile and main pancreatic ducts by a pancreatic head tumor (6).
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DISCUSSION
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The two most common causes of the double duct sign are carcinoma of the head of the pancreas and carcinoma of the ampulla of Vater. Other malignant causes are cholangiocarcinoma of the distal common bile duct, lymphoma, or metastasis. Benign causes include chronic pancreatitis and ampullary stenosis. Isolated case reports have identified primary retroperitoneal fibrosis and Kaposi sarcoma as rare potential causes (7–9).
The double duct sign was described initially by using ERCP (3,10,11), but this sign can also be seen with other modalities such as MR cholangiopancreatography (1,2), CT (4), and US (5).
Because the initial symptoms associated with pancreatic cancer are often insidious, the early diagnosis of a potentially resectable lesion remains difficult. The characteristic imaging findings are stenosis or obstruction of either the pancreatic duct, the common bile duct, or both, resulting in the double duct sign (12,13).
Most malignant pancreatic neoplasms are adenocarcinomas and of ductal origin, usually manifesting as a focal mass in the pancreatic head. MR cholangiopancreatography readily depicts the ducts obstructed by the pancreatic mass and localizes the obstruction to the pancreas. At MR cholangiopancreatography, dilatation of both the pancreatic and bile ducts (the double duct sign) is highly suggestive of but not diagnostic for pancreatic head malignancy (10,13–15).
In pancreatic head carcinoma, biliary and pancreatic duct dilatation occurs in 77% of cases (13). In another article (16), the double duct sign was seen in 13 (62%) of 21 patients with pancreatic carcinoma. A normal-sized pancreatic duct should not be excluded from a diagnosis of pancreatic head carcinoma because the ductal caliber will be normal in up to 20% of patients with pancreatic malignancy causing bile duct obstruction (14).
Carcinoma of the ampulla of Vater is defined as a malignant tumor arising in the last centimeter of the common bile duct, where it passes through the wall of the duodenum and ampullary papilla. The carcinoma typically manifests as a small tumor with marked bile duct dilatation, usually in association with mild to moderate dilatation of the pancreatic duct (16,17). In a previous article (16), the double duct sign was seen in 15 (52%) patients with ampullary carcinoma.
In conclusion, the double duct sign may be seen at MR cholangiopancreatography and other modalities such as ERCP, CT, and US. It is highly suggestive of but not diagnostic for pancreatic head malignancy.
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FOOTNOTES
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A trainee (resident or fellow) wishing to submit a manuscript for Signs in Imaging should first write to the Editor for approval of the sign to be prepared, to avoid duplicate preparation of the same sign.
Author stated no financial relationship to disclose.
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References
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