What is the characteristic sign of intraductal papillary mucinous neoplasms (IPMNs) on Endoscopic Retrograde Cholangiopancreatography (ERCP)?

Characteristic Sign of Intraductal Papillary Mucinous Neoplasms (IPMNs) on ERCP

The characteristic sign of intraductal papillary mucinous neoplasms (IPMNs) on ERCP is the "fish mouth" appearance of the papilla of Vater. 1

Endoscopic Features of IPMNs

Fish Mouth Appearance

• The patulous appearance of the papilla of Vater is referred to as "fish mouth papilla" due to its distinctive morphology
• This appearance is caused by mucus secretion from the prominent papilla of Vater
• This is a key diagnostic feature that helps distinguish IPMNs from other pancreatic lesions

Other ERCP Findings in IPMNs

• Dilated pancreatic ducts (main duct and/or branch ducts)
• Visible mucin extrusion from the ampulla
• Potential nodules in the cyst wall (concerning for invasive transformation)
• Filling defects within the pancreatic ducts

Diagnostic Approach to IPMNs

Imaging Modalities

1. ERCP: Demonstrates fish mouth papilla and mucin secretion
2. MRCP: Often considered gold standard for evaluating the entire outline of IPMNs 2
3. CT: Shows pancreatic cysts with ectasia of main pancreatic duct or dilated side branch ducts
4. EUS: Reveals mucus secretion and can identify mural nodules

Classification of IPMNs

• Main duct type: Involves the main pancreatic duct
• Branch duct type: Involves the side branches
• Mixed type: Involves both main duct and side branches

Clinical Significance

Malignant Potential

• Main duct and mixed type IPMNs have higher malignant potential
• Branch duct IPMNs are more frequently benign
• Presence of mural nodules increases malignancy risk in all types 3

Diagnostic Pitfalls

• ERCP may fail to show papillary tumors due to coexisting mucin or biliary sludge 4
• Secondary dilatation of pancreatic ducts due to obstructive processes can mimic IPMNs
• Small pancreatic ductal adenocarcinomas can lead to marked dilatation of the main duct, mimicking an IPMN 1

Management Implications

• Regular monitoring is important after surgery for disease recurrence
• Elevated CA 19-9 in patients with IPMN is concerning for malignant transformation 5
• Surgical resection is recommended for main duct IPMNs, mixed type IPMNs, and branch duct IPMNs with concerning features

In conclusion, the fish mouth appearance of the papilla of Vater on ERCP is the characteristic sign of IPMNs, not the fish eye sign. This distinctive appearance helps in the early diagnosis and management of these potentially malignant pancreatic lesions.