Ampullary adenocarcinomas are rare biliary tumors arising from the distal biliary epithelium at the ampulla of Vater.
Although classically presenting on imaging with the double duct sign, the tumor itself may be occult or of limited characterization on imaging.
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Epidemiology
These are rare tumors, with an adulthood estimated incidence of 0.7 in 100,000 men and 0.45 in 100,000 women in the United States 2.
There is an association with Gardner syndrome.
Clinical presentation
These patients typically present with obstructive jaundice and abdominal pain, but the presentation may be vague with other non-specific symptoms.
Radiographic features
Ultrasound, CT, and MRI may demonstrate the double duct sign (simultaneous dilatation of the common bile and pancreatic ducts) which is seen in ~52% of cases 1.
CT
may demonstrate a small, solid, enhancing tumor in the ampullary region protruding into the second portion of the duodenum 1
may show lobulated or infiltrative margins 1
discrete tumors may not be visible 1,3
CT cholangiogram is usually not performed given the presence of biliary obstruction and raised bilirubin levels
MRI
MRCP has been described as more sensitive than other imaging modalities for depicting ampullary lesions, but has low specificity 3.
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T2
may delineate the presence of an ampullary mass or papillary bulging
in addition to biliary tree dilatation, may show irregular narrowing of the distal common bile duct
DWI/ADC: there may be a degree of restricted diffusion which helps to differentiate it from benign lesions 3
Treatment and prognosis
Tumors that are occult on imaging are also frequently occult at ERCP/endoscopy, with the diagnosis only achieved after papillotomy/biopsy 1.
Differential diagnosis
papillitis
papillary stenosis (e.g. post-inflammatory)