AJR 2002; 179:1465-1471
© American Roentgen Ray Society
MR Cholangiopancreatography: Spectrum of Pancreatic Duct Abnormalities
John R. Leyendecker1,
Khaled M. Elsayes2,
Brett I. Gratz2 and
Jeffrey J. Brown2
1 Department of Radiology, University of Texas Health Science Center at San
Antonio, San Antonio, TX 78284-7800.
2 Mallinckrodt Institute of Radiology, Washington University School of Medicine,
510 S. Kingshighway Blvd., St. Louis, MO 63110.
Received January 7, 2002;
accepted after revision May 16, 2002.
Address correspondence to J. R. Leyendecker.
Introduction
Before the development of MR cholangiopancreatography (MRCP), an evaluation
of the pancreatic duct often required injection of endoscopic retrograde
contrast material. With the advent of MRCP, similar information can be quickly
obtained with minimal risk. MRCP also allows imaging of patients in whom
endoscopic retrograde cholangiopancreatography (ERCP) is unsuccessful and
reveals portions of the pancreatic duct upstream from an obstructing
lesion.
Technique
In our standard breath-hold technique, we obtain thin-section half-Fourier
single-shot turbo spin-echo images in multiple planes (TR/effective TE,
infinite/64; slice thickness, 3 mm; matrix, 162 x 256; with or without
fat saturation) and thick-slab rapid acquisition with relaxation enhancement
images in multiple oblique planes (infinite/1100; echo-train length, 240; slab
thickness, 5 cm; matrix, 240 x 256; with fat saturation; and field of
view, 250) (Fig.
1A,1B).
In our non-breath-hold protocol, we use a respiratory-triggered turbo
spin-echo sequence (1800/350; signal averages, 2; slice thickness, 1.5-2.0 mm;
matrix, 256x256; and field of view, 375). The relatively short effective
TE of the thin-slice images permits visualization of the pancreatic
parenchyma. For vascular and soft-tissue display, we also routinely include
fat-suppressed T2- and T1- weighted images and dynamic gadolinium-enhanced
fat-suppressed gradient-echo images of the pancreas because we believe that
imaging of the parenchyma is a valuable adjunct to MRCP. We do not routinely
use oral negative contrast agents, although they may occasionally be helpful
in suppressing signal from the overlying bowel
(Fig. 2).
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Fig. 1A. —63-year-old-woman with endoscopically confirmed intraductal
papillary mucinous tumor. Maximum-intensity-projection image of multiple 4-mm
fat-suppressed HASTE images (TR/effective TE, infinite/64) acquired during
single breath-hold shows main pancreatic duct dilatation and prominent branch
ducts (arrows). Note that this image can be viewed in any projection,
but image quality may be limited by slice thickness and stairstep
artifacts.
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Fig. 1B. —63-year-old-woman with endoscopically confirmed intraductal
papillary mucinous tumor. Thick-slab rapid acquisition with relaxation
enhancement MR image (TR/TE, infinite/1100) also shows main pancreatic duct
dilatation and prominent branch ducts (arrows). However, this image
cannot be manipulated.
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Fig. 2. —16-year-old girl with chronic pancreatitis. MR
cholangiopancreatogram obtained with oral iron-based negative contrast agent
shows no signal from bowel. Pancreatic duct stricture (arrow) is
visible.
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Congenital Anomalies
Pancreas Divisum
An anatomic variant, pancreas divisum occurs in 5-14% of the population and
results from the failure of the dorsal and ventral pancreatic primordia to
fuse. The dorsal duct drains into the duodenum at the minor papilla, and the
ventral duct drains via the major ampulla with the common bile duct
(Fig. 3). On axial images,
pancreas divisum is easily recognized because in patients with this variant
the dorsal duct passes the terminal common bile duct anteriorly and superiorly
(Fig. 4). MRCP easily reveals
the dorsal pancreatic duct in patients with divisum, whereas cannulation of
the minor papilla of such patients for ERCP is frequently unsuccessful
[1]. Infrequently, pancreas
divisum is associated with a focal dilatation of the distal dorsal duct near
the minor papilla, a condition referred to as santorinicele
[2].
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Fig. 3. —39-year-old woman with history of pancreatitis thought to
have been caused by ethanol abuse. Thick-slab MR cholangiopancreatogram shows
separate dorsal (small arrow) and ventral (large arrow)
pancreatic duct systems consistent with divisum, which was confirmed on ERCP
(not shown).
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Annular Pancreas
An annular pancreas may cause neonatal duodenal obstruction and can be
diagnosed on the basis of MR imaging findings that reveal pancreatic tissue
and an annular duct surrounding the descending duodenum (Fig.
5A,5B).
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Fig. 5A. —15-year-old girl with recurrent pancreatitis and annular
pancreas as well as history of intestinal bypass for duodenal obstruction.
Maximum-intensity-projection image from respiratory-triggered thin-slice turbo
spin-echo MR cholangiopancreatogram (TR/TE, 1800/350; signal averages, 2;
slice thickness, 2 mm) shows dilated annular duct (arrowhead)
surrounding duodenum (large arrow). Bypass loop (small
arrow) can be seen.
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Fig. 5B. —15-year-old girl with recurrent pancreatitis and annular
pancreas as well as history of intestinal bypass for duodenal obstruction.
Coronal HASTE image shows pancreatic tissue (arrows) surrounding
duodenum (arrowhead).
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Trauma
The diagnosis of pancreatic duct injury in the setting of trauma is
critical to subsequent treatment of the patient. MRCP can accurately depict
the integrity of the pancreatic duct as well as the site of disruption
[3,
4]
(Fig. 6). More important, MRCP
can reveal the duct that is upstream from the site of disruption, a task that
may be difficult with ERCP.
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Fig. 6. —26-year-old man who experienced blunt abdominal trauma.
Maximum-intensity-projection image from respiratory-triggered thin-slice turbo
spin-echo MR cholangiopancreatogram obtained 2 weeks after injury shows
disruption of main pancreatic duct (arrow) with associated fluid
collection (arrowhead).
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Inflammatory Conditions
Acute Pancreatitis
MR imaging does not play a critical role in establishing the diagnosis of
acute pancreatitis, but when combined with parenchymal imaging, MRCP may aid
in elucidating an underlying cause and in identifying complications. In
contrast to chronic pancreatitis and pancreatic cancer, the pancreatic duct in
patients with acute pancreatitis is typically smooth and of normal caliber.
However, compression of the duct by adjacent inflammation and edema may occur
(Fig.
7A,7B).
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Fig. 7B. —Acute pancreatitis in 30-year-old man with
hypertriglyceridemia. Contrast-enhanced interpolated three-dimensional spoiled
gradient-echo MR image (TR/TE, 4.5/1.9; flip angle, 15°; effective slice
thickness, 2 mm) shows pancreatic necrosis (arrow) in head and
uncinate process causing duct compression seen in A.
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Chronic Pancreatitis
Manifestations in the pancreatic duct signaling the presence of chronic
pancreatitis include strictures (Fig.
2), dilatation of the main duct and side branches
(Fig. 8), pseudocyst and
fistula formation (Fig. 8),
and intraductal calculi (Fig.
9A,9B).
In addition, acute or chronic pancreatitis may be complicated by secondary
infection with pyogenic organisms (Fig.
10). Unfortunately, the manifestations of chronic pancreatitis on
MRCP may overlap with imaging findings of adenocarcinoma or an intraductal
mucinous tumor (which is discussed later in this article). Dilatation of the
common bile duct and main pancreatic duct (the double-duct sign), which is a
finding typically associated with adenocarcinoma, may be seen in patients with
chronic inflammation and may be associated with an inflammatory mass mimicking
a neoplasm (Fig.
11A,11B).
Visualization of a mass penetrated by an unobstructed pancreatic duct makes
inflammation a likely cause (duct-penetrating sign)
[5].
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Fig. 8. —Surgically confirmed chronic pancreatitis in 40-year-old man.
Thick-slab MR cholangiopancreatogram shows dilatation of main pancreatic duct
(chain of lakes sign) with branch duct ectasia (long arrow) and
communicating pseudocysts (arrowheads). Communication of pseudocysts
with main pancreatic duct was confirmed on thin-section MR images (not shown).
Note pseudocyst in pancreatic head (short arrow) contains debris.
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Fig. 9A. —Surgically confirmed pancreatic duct stone in 63-year-old
woman with chronic pancreatitis. Thick-slab MR cholangiopancreatogram shows
dilated pancreatic duct containing filling defect (arrow).
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Fig. 9B. —Surgically confirmed pancreatic duct stone in 63-year-old
woman with chronic pancreatitis. Axial half-Fourier single-shot turbo
spin-echo MR image confirms filling defect (arrow). On subsequent
contrast-enhanced images (not shown), no enhancement of filling defect was
noted.
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Fig. 10. —69-year-old man with chronic pancreatitis and pancreatic
abscess caused by Pseudomonas infection. Axial HASTE image shows
markedly dilated pancreatic duct (thin arrow) and adjacent abscess
(thick arrow), which on ERCP (not shown) freely communicated.
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Fig. 11A. —Surgically confirmed acute and chronic pancreatitis in
19-year-old woman. Thick-slab MR cholangiopancreatogram shows double-duct sign
with pancreatic duct stricture (arrow) confirmed on ERCP (not shown).
Note bifid pancreatic duct (arrowheads) in tail, a normal
variant.
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Fig. 11B. —Surgically confirmed acute and chronic pancreatitis in
19-year-old woman. Early-phase contrast-enhanced two-dimensional spoiled
gradient-echo MR image shows inflammatory mass (arrow) in uncinate
process.
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Pancreatic Neoplasms
Adenocarcinoma
Most malignant pancreatic tumors are adenocarcinomas originating in the
ducts, typically in the pancreatic head. Most patients with ductal
adenocarcinoma have dilatation of the bile duct, the pancreatic duct, or both
[6]. An abrupt obstruction of
the pancreatic duct associated with atrophy of the gland should raise concern
about the presence of pancreatic carcinoma
(Fig. 12). Occasionally,
ductal dilatation may be the only direct imaging sign of pancreatic cancer
(Fig. 13). As in inflammatory
conditions, parenchymal imaging is an important adjunct to MRCP for the
evaluation of neoplastic conditions of the pancreas.
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Fig. 13. —Pancreatic adenocarcinoma in 57-year-old woman. Thick-slab MR
cholangiopancreatogram shows obstructed pancreatic duct (arrowhead)
with ectatic branch ducts (arrow). Common bile duct was stented for
obstruction. A 1.6-cm carcinoma found at surgery could not be seen even in
retrospect on contrast-enhanced MR images of pancreas (not shown).
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Intraductal Papillary Mucinous Tumor
Intraductal papillary mucinous tumor of the pancreas originates in the
ductal epithelium, shows a papillomatous growth pattern, and produces mucin,
resulting in ductal dilatation or cyst formation. A simple classification
system divides this entity into two groups on the basis of location: main duct
and branch duct. Features of both types may coexist in a single patient.
Main duct intraductal papillary mucinous tumor is associated with diffuse
or segmental dilatation of the main pancreatic duct (Figs.
1A,1B
and 14). Main duct intraductal
papillary mucinous tumor may be indistinguishable from chronic pancreatitis on
MRCP because mucin resembles fluid on T2-weighted MR images
[7]. Chronic pancreatitis may
coexist with intraductal papillary mucinous tumor. A malignant main duct type
of this tumor displays greater dilatation and more diffuse involvement of the
main pancreatic duct than the benign variety of the tumor
[8].
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Fig. 14. —Surgically confirmed intraductal papillary mucinous tumor in
60-year-old woman. Thickslab MR cholangiopancreatogram shows marked dilatation
of duct (arrow) in tail of pancreas associated with diffuse moderate
dilatation of more distal duct and branch duct ectasia
(arrowhead).
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The branch duct type of intraductal papillary mucinous tumor occurs most
frequently in the uncinate process but may arise anywhere in the pancreas. A
branch duct type tumor can appear as either unilocular or multilocular, and
communication with the main pancreatic duct may be visible on MRCP (Fig.
15A,15B).
The differential diagnosis for branch duct intraductal papillary mucinous
tumor on MRCP includes such entities as a mucinous cystadenoma, mucinous
cystadenocarcinoma, and pancreatic cyst or pseudocyst. The presence of filling
defects (Fig.
16A,16B,16C)
suggests malignancy, as does enlargement of the main pancreatic duct
associated with a branch duct type tumor
[8].
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Fig. 15A. —Surgically confirmed intraductal papillary mucinous tumor in
55-year-old man. Thick-slab MR cholangiopancreatogram shows cystic dilatation
of branch duct (arrow) in head of pancreas and moderate dilatation of
main pancreatic duct.
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Fig. 15B. —Surgically confirmed intraductal papillary mucinous tumor in
55-year-old man. Coronal HASTE image shows communication of ectatic branch
duct with main pancreatic duct (arrow). Arrowhead denotes distal
common bile duct.
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Fig. 16A. —Surgically confirmed intraductal papillary mucinous tumor in
69-year-old man. Thick-slab MR cholangiopancreatogram reveals large cystic
mass (arrow) in head of pancreas associated with main pancreatic duct
dilatation, diffuse branch duct ectasia, and tiny cysts (arrowhead)
elsewhere. At pathologic examination, mucinous cysts were found throughout
pancreas corresponding to cysts seen on MR images.
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Fig. 16C. —Surgically confirmed intraductal papillary mucinous tumor in
69-year-old man. Contrast-enhanced fat-suppressed three-dimensional spoiled
gradient-echo MR image obtained through cystic mass shown in B displays
enhancement of soft-tissue component (arrow).
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Conclusion
MRCP depicts a spectrum of pancreatic duct abnormalities and may reveal
abnormalities or portions of the pancreatic duct not visualized on ERCP.
Several entities result in dilatation of the main pancreatic duct, and overlap
exists between some inflammatory and neoplastic conditions.
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Introduction
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