Diagnostic Ultrasound - Abdomen and Pelvis

Intraductal Papillary Mucinous Neoplasm (IPMN)
TERMINOLOGY
Abbreviations
• Intraductal papillary mucinous neoplasm (IPMN)
Synonyms
• Intraductal papillary mucinous tumor, duct ectatic
mucinous cystadenoma, mucinous hypersecretory
neoplasm, mucin-producing tumor
Definitions
• Cystic neoplasm of pancreas arising from mucin-producing
epithelium of main pancreatic duct (MPD) &/or side branch
pancreatic ducts (SBD) with variable malignant potential
IMAGING
General Features
• Best diagnostic clue
○ Grossly dilated MPD without obstructive mass
○ Cystic lesion in pancreatic head or uncinate process with
small cystic loculations and communication to MPD
• Location
○ Typically in head/uncinate
○ May be multiple (21-40%); can involve entire pancreas in
up to 20% of cases
• Size
○ Side branch cysts typically 0.5-2.0 cm; can grow > 3 cm
• Morphology
○ MPD type: Dilated MPD (> 5 mm); no obstructive cause
○ SBD type: Multicystic lesion contiguous with the MPD
○ Mixed type: Findings of both types
Ultrasonographic Findings
• MPD type: Dilated MPD, may contain low-level internal
echoes (mucin vs. mural nodule)
• SBD type: Anechoic or hypoechoic cystic mass ± septations;
may see communication with PD if it is dilated
Other Modality Findings
• Endoscopic ultrasound (EUS)
○ Higher spatial resolution than transabdominal US; can
depict internal septations, mural nodules, wall thickening
○ Used to guide aspiration of cyst contents and biopsy of
soft tissue components
– Cyst contents: High CEA levels with malignancy; < 5
ng/mL excludes mucinous lesion
Radiographic Findings
• Endoscopic retrograde cholangiopancreatography (ERCP)
○ Bulging "fish eye" ampulla of Vater, pathognomonic for
IPMN
○ Dilated MPD with filling defects due to excessive mucin
production; cystic dilatation of branch ducts
○ Traditionally used to show communication with MPD
CT Findings
• MPD type: > 5 mm, tortuous; segmental or diffuse
• SBD-type: Multilocular cystic lesion with possible
communication to MPD
○ Grape-like clusters of small cysts or tubes and arcs; may
be multifocal
• CECT may show enhancing soft tissue thickening or mural
nodularity
MR Findings
• T1WI: Hypointense
• T2WI: Hyperintense for both SBD and BPD-types
○ SBD: Focal or multifocal, lobulated, cystic lesion with thin
internal septations
– Clustered small T2-bright cysts; ± curvilinear T2-
hyperintense connection to MPD
• MRCP
○ T2-hyperintense ductal communication best depicted
with thin slice and thick slab techniques
○ May show intraductal nodules as filling defects → raising
concern for malignant conversion
○ Can assess for biliary obstruction in setting of malignancy
• T1WI C+
○ Typically shows lack of enhancing components
○ Enhancing soft tissue thickening or nodularity within
duct or cystic mass suggests malignant conversion
Imaging Recommendations
• Best imaging tool
○ CT or MR important in identifying features associated
with increased risk of malignancy
○ EUS: ↑ overall accuracy for diagnosis over CT and MR
– Invasive technique
– Best morphologic evaluation and can guide cyst
aspiration/biopsy
○ MRCP
– Best noninvasive imaging modality for identification
of ductal communication
• Protocol advice
○ Initial evaluation and morphologic characterization of
pancreatic cystic lesions > 1 cm
– CECT with curved planar reconstructions; or CE MR
with MRCP (angled to MPD)
– To assess for high-risk stigmata or worrisome features
○ Follow-up surveillance imaging with CE MR/MRCP
DIFFERENTIAL DIAGNOSIS
Mucinous Cystic Pancreatic Neoplasm
• Solitary; no communication with MPD; may contain
peripheral calcification
• Typically in body/tail of pancreas in middle-aged women
Pancreatic Serous Cystadenoma
• Solitary; no communication with MPD; may contain spoke
wheel calcification
• Commonly in body/tail of pancreas in elderly women
Chronic Pancreatitis
• Atrophic pancreas, dilated ducts, parenchymal calcifications
Pancreatic Pseudocyst
• Possible communication with MPD or SBD
• Findings &/or history of acute or chronic pancreatitis
Pancreatic Ductal Adenocarcinoma
• Solid, infiltrative mass obstructing the MPD
Diagnoses: Pancreas
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