Biliary IPMN

Massively dilated bile ducts (either diffuse or localized) filled with mucin

Mural nodules best visualized after removal of mucin

Biliary dilation both proximal and distal to mural nodule

• CT/MR: Markedly dilated intra-/extrahepatic bile ducts with mural nodularity or discrete intraductal mass

Attenuation and MR signal characteristics of mucin distending ducts is similar to normal bile

Presence of mural nodularity or soft tissue suggests presence of malignancy

PATHOLOGY

• Unknown etiology, but associations with hepatolithiasis and Clonorchis suggest chronic biliary inflammation may be causative

CLINICAL ISSUES

• Most common in elderly patients from East Asia

• May present with repeated episodes of cholangitis and jaundice

• Biliary IPMN localized to intrahepatic ducts may be treated with partial hepatectomy if tumor is relatively localized

• Resection of the common duct with Roux-en-Y anastomosis may be required for tumors involving either extrahepatic duct or right/left main ducts

• Stenting or drainage to alleviate jaundice in patients who are not surgical candidates

• Multifocality frequent, and recurrences after surgery are common due to small foci of undetected disease in biliary tree distant from site of resection

(Left) Graphic of biliary intrapapillary mucinous tumor demonstrates the segmental distension of the right lobe intrahepatic ducts , which are filled with mucin and contain a mucosal mass arising from the ductal epithelium.

(Right) Axial T1WI MR with gadolinium in a woman with midepigastric pain and elevated alkaline phosphatase shows fusiform dilatation of the left bile ducts , which proved to be biliary IPMN at surgery.

(Left) Axial CECT in a patient presenting with RUQ pain and elevated alkaline phosphatase demonstrates atrophy of the left lobe and marked dilation of the left bile duct greater than the right. ERCP and subsequent surgery revealed a left duct biliary IPMN.

(Right) Axial CECT shows asymmetric left biliary ductal dilatation and subtle enhancing nodularity within the proximal left duct . Intraductal cholangiocarcinoma and background biliary IPMN were identified at histology. (Courtesy S. Yeon Kim, MD.)

TERMINOLOGY

Abbreviations

• Intraductal papillary mucinous neoplasm (IPMN) of bile ducts

Synonyms

• Intraductal papillary neoplasm of liver, mucin-secreting biliary papillomatosis, mucin-producing cholangiocarcinoma, mucinous ductal ectasia of biliary tree

Definitions

• Mucin-producing papillary neoplasm arising from biliary mucosa

Only recently added to WHO classification in 2010

Significant overlap with biliary papillomatosis, and some authors suggest they are same entity

IMAGING

General Features

• Best diagnostic clue

Diffuse segmental “aneurysmal” dilation of bile ducts with a polypoid or nodular intraductal mass

Biliary dilation both proximal and distal to mural nodule due to mucin hypersecretion

• Location

Intra-/extrahepatic bile ducts: Most common locations are left liver lobe ducts and liver hilum

• Size

• Morphology

“Aneurysmal,” marked dilatation of mucin-distended ducts

Radiographic Findings

• ERCP

Extrusion of clear mucin from patulous ampulla visible to endoscopist due to mucin hypersecretion by tumor

Massively dilated bile ducts (either diffuse or localized) filled with mucin

– Mucin-filled bile ducts may result in nonvisualization of affected segment(s) due to difficulty of filling mucin-filled ducts with contrast

– Amorphous filling defects in dilated ducts may representing either mucin plugs or tumor

Mural nodules best visualized after removal of mucin

CT Findings

• Markedly dilated intra-/extrahepatic bile ducts with mural nodularity or discrete intraluminal papillary/fungating mass

Attenuation of mucin distending ducts is similar to normal bile

– Mucin within ducts cannot be differentiated from normal bile on CT

Presence of mural nodularity or soft tissue component should suggest presence of malignancy

• CT cholangiography may play a role in preoperative diagnosis and determination of tumor resectability: Mucin (and tumor) outlined by biliary contrast

MR Findings

• Diffuse or segmental biliary ductal dilatation with bile duct contents appearing hyperintense on T2WI and hypointense on T1WI (similar to normal bile)

Mucin within ducts cannot be differentiated from normal bile on MR

ERCP/MRCP mismatch: Mucin-filled duct is not visible on ERCP while it is seen on MRCP

Hepatobiliary contrast agents (i.e., Eovist) may demonstrate nonfilling of affected ducts (i.e., those filled with mucin), similar to ERCP

• Papillary projections or discrete soft tissue masses within dilated ducts appear hypointense on T1WI, hyperintense on T2WI, and enhancing on T1WI C+