DOI:10.2214/AJR.04.1775
AJR 2006; 186:499-506
© American Roentgen Ray Society
Diagnosis of Duct Disruption and Assessment of Pancreatic Leak with Dynamic Secretin-Stimulated MR Cholangiopancreatography
A. R. Gillams1,
T. Kurzawinski2 and
W. R. Lees1
1 Department of Medical Imaging, The Middlesex Hospital and University College
London Medical School, Mortimer St., London W1T 3AA, England.
2 Department of Surgery, The Middlesex Hospital and University College London
Medical School, London, England.
Received November 16, 2004;
accepted after revision January 27, 2005.
Address correspondence to A. R. Gillams.
Abstract
OBJECTIVE. The management of pancreatic duct disruption is complex
and depends on several factors including the cause, morphology, and degree of
disruption. ERCP can show duct disruption in as many as 75% of patients but is
invasive and cannot detect disruption beyond an obstruction. We studied the
role of secretin MR cholangiopancreatography in patients with suspected
pancreatic duct disruption.
CONCLUSION. Secretin MR cholangiopancreatography is a safe,
noninvasive test that can provide additional useful information about duct
integrity and facilitate management.
Keywords: abdominal imaging • MRI • pancreas • pancreatitis • trauma
Introduction
The causes of pancreatic duct disruption include acute pancreatitis,
chronic pancreatitis, surgery, and trauma. Persistent disruption can result in
fluid collections, ascites, or fistulas and has a significant impact on the
clinical course. Small side-branch disruptions can heal without long-term
sequelae, but main-duct disruption can result in strictures, secondary
recurrent acute pancreatitis, pancreatic atrophy, and eventually endocrine and
exocrine insufficiency. Current treatment options include surgery, endoscopic
intervention, or conservative management
[1-3].
Timely diagnosis of duct disruption, its location, and the size of the leak is
essential for choosing the appropriate treatment
[4]. The clinical setting,
ductal anatomy, and parenchymal anatomy also affect the choice of therapy.
Cross-sectional imaging can be used to infer the presence and degree of
disruption [5], although CT can
be unreliable in the early diagnosis of pancreatic trauma
[6]. MR
cholangiopancreatography (MRCP) has been used in trauma patients to show
peripancreatic fluid collections and the ductal anatomy
[7,
8], but only ERCP has been able
to provide dynamic information as to whether there is continuing leakage from
the duct [9]. Even then, ERCP
fails to reveal the disruption in as many as 25% of instances
[10]. Nonvisualization of a
disruption is more likely to result in therapeutic failure, either surgical or
endoscopic [10,
11]. ERCP also carries the
risk of introducing infection and the theoretic risk of exacerbating a leak by
contrast injection at nonphysiologic pressures
[12]. Secretin MRCP is a
noninvasive test that has been used successfully to improve the delineation of
ductal anatomy, to assess patients after surgical and endoscopic intervention,
and to measure pancreatic exocrine function
[13-15].
The aim of this study was to investigate the use of secretin MRCP in the
depiction of duct disruption.
Subjects and Methods
Patients
The study population comprised 17 patients (13 males and 4 females; age
range, 10-71 years; median, 39 years) with suspected duct disruption. Eight
patients had sustained a pancreatic injury, which had occurred from blunt
abdominal injury in five, after retroperitoneal surgery in two, and after ERCP
in one. The other nine had had acute pancreatitis, which was secondary to
alcohol in four, secondary to gallstones in three, induced by ERCP in one, and
induced by high-dose steroids for an astrocytoma in one. Two of the four
patients with alcohol-induced acute pancreatitis had underlying chronic
pancreatitis. Subsequent management, imaging follow-up, and clinical course
after MRCP were recorded from the patients' charts and radiologic records.
Clinical end points were the resolution of peripancreatic fluid collections or
ascites and the need for surgery. Mean follow-up was 6 months (range, 2-54
months).
MRI Technique
MRI was performed on a 1.5-T standard, commercially available system with
25 mT/m gradients (Vision, Siemens Medical Solutions) using a torso
phased-array coil. All patients took no food or water by mouth for 4 hr before
MRI. All sequences were obtained during a single breath-hold; antispasmodics
were not administered. A coronal steady-state-precession (TRUFISP) sequence
(TR/TE, 6.3/3.0; flip angle, 70°; slice thickness, 6 mm; field of view,
400 x 400; matrix, 256 x 256; 12 slices acquired in 19 sec), an
axial TRUFISP (6.3/3.0; flip angle, 70°; slice thickness, 7 mm; field of
view, 312 x 420; matrix, 192 x 256; 12 slices acquired in 14 sec),
and a T1-weighted, gradient-echo sequence (174.9/4.1; flip angle, 80°;
slice thickness, 5 mm; field of view, 280 x 450; matrix, 107 x
256; 19 slices acquired in 18 sec) were performed. MRCP was performed using a
multislice, single-shot fast spin-echo (SSFSE) sequence (2,800/110; flip
angle, 150°; slice thickness, 10–15 mm; field of view, 394 x
450; matrix, 240 x 256; 5 slices acquired in 29 sec) or a heavily
T2-weighted HASTE sequence (11.9/95; flip angle, 150°; slice thickness, 5
mm; field of view, 394 x 450; matrix, 208 x 256; 13 slices
acquired in 17 sec). Secretin (0.1 mL/kg) (Secrelux, Sanochemia) was
administered as an IV injection over 20 sec. The TRUFISP sequences or the
multislice SSFSE was repeated after secretin. In the case of the SSFSE, the
same slice position and receiver gain were used both before and after secretin
administration and the sequence was repeated at 2-min intervals for 7 min
after secretin administration.
Image Analysis
The parenchymal images images were studied for evidence of parenchymal
continuity, laceration, or changes in signal intensity. A partial laceration
was defined as one in which some parenchyma remained in continuity, and a
full-thickness laceration was defined as one with no continuity. The
percentage of parenchymal disruption was estimated. The presence, location,
and relationship of any peripancreatic fluid collection or free fluid were
recorded. Where fluid followed the contours of adjacent structures, it was
considered free; contained and focal pockets of fluid were considered
collections. Duct size, continuity, and relationship to collections or free
fluid were noted. Duct size was measured with electronic calipers. A duct
diameter of greater than 3 mm was considered abnormal. After secretin
administration, changes in duodenal fluid content and the size or signal
intensity of peripancreatic fluid collections were recorded. In healthy
patients, secretin administration increases duodenal and jejunal fluid
content, with or without a mild (< 1 mm), transient increase in duct
diameter. Any increase in fluid outside these regions constitutes an abnormal
leakage of pancreatic fluid and indicates ductal disruption. Regions of
interest were drawn around any peripancreatic fluid or collection, and the
signal intensity was recorded on the pre- and postsecretin SSFSE images,
because an increase in signal intensity indicates an increase in fluid content
on this water-only SSFSE sequence.
Results
No complications occurred after secretin MRCP. A summary of the MRI
findings, management, and outcome is provided in Tables
1 and
2. Three patients had both
focal fluid collections and free fluid, 13 had focal fluid collections alone,
and one had a drain at the site of a previous collection. Five patients had
some degree of parenchymal disruption: one full thickness and four partial.
Eleven patients had a dilated main pancreatic duct, and six had a duct of
normal caliber. Ten patients had duct disruption as evidenced by increasing
peripancreatic fluid collections after secretin (Figs.
1A,
1B,
1C,
1D,
2A,
2B,
2C,
2D, and
2E). Five patients underwent
surgery, and a sixth was treated with endoscopic stenting; all recovered well.
Duct disruption was confirmed at surgery in all five. Three patients were
managed conservatively and continued to have collections, ascites, or fistulas
on follow-up at 5, 11, or 12 months, respectively. In the tenth patient, who
sustained a pancreatic duct perforation after ERCP, the site of duct
disruption and the patient's anomalous anatomy—a forme fruste
divisum—were clearly shown. Because further endoscopic intervention
carried the risk of exacerbating the situation, a trial of conservative
therapy was undertaken (Figs.
3A,
3B,
3C,
3D, and
3E). Follow-up secretin MRCP 3
weeks later showed that the perforation had healed, and the patient made a
full recovery on conservative therapy.
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Fig. 1A —14-year-old boy who sustained blunt trauma to abdomen. Axial TRUFISP
and coronal MR cholangiopancreatography images obtained using fast imaging
with steady-state precession sequence before (A and B) and after
(C and D) secretin. Collection increases in head of pancreas
(arrows) after secretin, indicating continuing duct disruption. Also
seen are free fluid around liver and increase in duodenal fluid content after
secretin administration.
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Fig. 1B —14-year-old boy who sustained blunt trauma to abdomen. Axial TRUFISP
and coronal MR cholangiopancreatography images obtained using fast imaging
with steady-state precession sequence before (A and B) and after
(C and D) secretin. Collection increases in head of pancreas
(arrows) after secretin, indicating continuing duct disruption. Also
seen are free fluid around liver and increase in duodenal fluid content after
secretin administration.
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Fig. 1C —14-year-old boy who sustained blunt trauma to abdomen. Axial TRUFISP
and coronal MR cholangiopancreatography images obtained using fast imaging
with steady-state precession sequence before (A and B) and after
(C and D) secretin. Collection increases in head of pancreas
(arrows) after secretin, indicating continuing duct disruption. Also
seen are free fluid around liver and increase in duodenal fluid content after
secretin administration.
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Fig. 1D —14-year-old boy who sustained blunt trauma to abdomen. Axial TRUFISP
and coronal MR cholangiopancreatography images obtained using fast imaging
with steady-state precession sequence before (A and B) and after
(C and D) secretin. Collection increases in head of pancreas
(arrows) after secretin, indicating continuing duct disruption. Also
seen are free fluid around liver and increase in duodenal fluid content after
secretin administration.
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Fig. 2A —49-year-old man with acute pancreatitis complicated by development
of collection that was drained via transgastric route but failed to resolve.
Coronal TRUFISP obtained using fast imaging with steady-state precession
sequence shows mixed-signal-intensity collection in body of pancreas
(black arrow). Normal duct is present in head and neck (white
arrow).
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Fig. 2B —49-year-old man with acute pancreatitis complicated by development
of collection that was drained via transgastric route but failed to resolve.
Axial T1-weighted image shows collection in body of pancreas (arrow),
with parenchyma of normal signal intensity in tail.
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Fig. 2C —49-year-old man with acute pancreatitis complicated by development
of collection that was drained via transgastric route but failed to resolve.
Sequential maximum intensity projections before secretin (C) and 3
(D) and 7 (E) min after secretin administration. Fluid signal
intensity increases in pancreatic collection (arrows) after secretin,
indicating continuing duct disruption and communication with cyst. Duct in
tail is mildly dilated before secretin administration and dilates further
after secretin administration.
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Fig. 2D —49-year-old man with acute pancreatitis complicated by development
of collection that was drained via transgastric route but failed to resolve.
Sequential maximum intensity projections before secretin (C) and 3
(D) and 7 (E) min after secretin administration. Fluid signal
intensity increases in pancreatic collection (arrows) after secretin,
indicating continuing duct disruption and communication with cyst. Duct in
tail is mildly dilated before secretin administration and dilates further
after secretin administration.
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Fig. 2E —49-year-old man with acute pancreatitis complicated by development
of collection that was drained via transgastric route but failed to resolve.
Sequential maximum intensity projections before secretin (C) and 3
(D) and 7 (E) min after secretin administration. Fluid signal
intensity increases in pancreatic collection (arrows) after secretin,
indicating continuing duct disruption and communication with cyst. Duct in
tail is mildly dilated before secretin administration and dilates further
after secretin administration.
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Fig. 3A —39-year-old woman, referred from another hospital, with
retroperitoneal collection that had developed after ERCP. Axial T1-weighted
image shows right-sided mixed-signal-intensity collection in retroperitoneum
(arrow).
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Fig. 3B —39-year-old woman, referred from another hospital, with
retroperitoneal collection that had developed after ERCP. Baseline MR
cholangiopancreatography (MRCP) image before secretin administration shows
anatomic variant with dorsal duct predominantly draining via accessory papilla
(solid arrow) and relatively small duct of Wirsung (dashed
arrow).
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Fig. 3C —39-year-old woman, referred from another hospital, with
retroperitoneal collection that had developed after ERCP. Sequential MRCP
sequences after secretin administration show fluid leaking from duct of
Wirsung (arrows).
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Fig. 3D —39-year-old woman, referred from another hospital, with
retroperitoneal collection that had developed after ERCP. Sequential MRCP
sequences after secretin administration show fluid leaking from duct of
Wirsung (arrows).
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Fig. 3E —39-year-old woman, referred from another hospital, with
retroperitoneal collection that had developed after ERCP. Secretin MRCP
repeated after 3 weeks of pancreatic rest with total parenteral nutrition and
percutaneous drainage of retroperitoneal fluid collection. Duct no longer
shows leakage (arrow). Abnormal dilatation of dorsal duct indicates
inadequate drainage from accessory papilla—that is, functional
obstruction in forme fruste divisum.
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Fig. 4A —24-year-old man who sustained blunt abdominal trauma. Axial
contrast-enhanced CT scan shows fluid collection (arrow) around
superior mesenteric vessels and extending into anterior abdomen.
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Fig. 4B —24-year-old man who sustained blunt abdominal trauma. Maximum
intensity projections of MRCP sequence before (B) and after (C)
secretin administration. Fluid content of duodenum, including duodenal cap
(arrows), increases, but no fluid leak from pancreatic duct is
present.
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Fig. 4C —24-year-old man who sustained blunt abdominal trauma. Maximum
intensity projections of MRCP sequence before (B) and after (C)
secretin administration. Fluid content of duodenum, including duodenal cap
(arrows), increases, but no fluid leak from pancreatic duct is
present.
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Seven patients showed no leak after secretin administration (Figs.
4A,
4B, and
4C); five responded to
conservative therapy although one of those five underwent percutaneous
necrosectomy for residual solid pancreatic phlegmon. The fluid component of
the phlegm and the percutaneous sinus had resolved on conservative treatment.
In the sixth patient, the surgeon elected to operate, and the seventh patient
failed to respond to conservative treatment and eventually underwent surgery.
In this patient, a tubogram showed the percutaneous drain to be directly
continuous with the main pancreatic duct. This secretin MRCP result was
classified as false-negative and probably had been due to the drain's not
being clamped before the study, causing the pancreatic juice to flow directly
into the drain without pooling around the pancreas.
Five patients underwent ERCP, which, in two, showed proximal obstruction
that prevented depiction of the distal duct or of the disruption; in two,
confirmed disruption; and in one, confirmed the absence of disruption.
Discussion
Secretin MRCP contributed to the successful management of 12 of 17 patients
and correctly predicted that three other patients would continue to have
problems with fistulas and collections. Of these 12, six with disruption
underwent definitive intervention and recovered well, and five with no
disruption responded to conservative therapy. The clinical course of the 12th
patient was more complicated, but the secretin study directed initial
conservative therapy because of the presence of complex anatomy, and a second
secretin study confirmed the success of conservative therapy 3 weeks later. In
two patients, the secretin study was noncontributory: In one, the findings had
been false-negative; in the other, the surgeon elected to operate despite the
absence of a leak. In 10 of 12 patients, the secretin study provided
additional information that could not be derived from standard cross-sectional
imaging. In two of 12, both of whom were trauma patients, the cross-sectional
imaging showed a laceration of greater than 50%, strongly suggestive of
disruption, and the secretin study confirmed leakage. In the acute
pancreatitis patients, assessment of the likelihood of disruption from
cross-sectional imaging was more complex, because complete disruption is not
necessarily associated with continuing leakage. Secretin MRCP provided more
complete information than did ERCP. Of the five patients who underwent ERCP,
duct obstruction prevented depiction of the disruption in two (40%), in both
of whom the disruption was shown by secretin MRCP.
The management of pancreatic disruption is complex and depends on multiple
factors, including the cause of the disruption, the clinical condition of the
patient, the parenchymal and ductal anatomy, and the degree of disruption.
Historically, only ERCP has been able to provide dynamic information about
continuing duct disruption. Many surgeons are reluctant to perform an invasive
test, particularly on young children after trauma. ERCP may fail to show the
disruption because of duct obstruction proximal to it, and overfilling of the
duct in pancreatic disruption is actively discouraged because of the risk of
sepsis [12]. Secretin MRCP is
a noninvasive technique that can show the whole pancreatic anatomy, both the
parenchyma and the ducts; any peripancreatic fluid collections; and
disruption, including a leak, beyond an obstructed duct. Secretin MRCP thus
provides all the information available from CT plus a more complete assessment
of the duct than often can be obtained on ERCP and dynamic information about
ongoing leakage. One caveat is that percutaneous drains should be clamped
before secretin MRCP and the abdomen examined for any sinus tracts, which need
to be monitored clinically or included in the images. This precaution should
reduce the chances of false-negative findings, as occurred in our series.
Some centers view acute pancreatitis as a direct contraindication to
secretin administration, because pancreatic stimulation theoretically could
exacerbate the inflammatory process. Others have performed secretin MRCP in
the setting of acute pancreatitis without difficulty
[16]. We generally do not
administer secretin within 3 weeks of the onset of an acute episode of
pancreatitis. Although nausea and vomiting have been reported after bolus
injection of secretin, these side effects can be avoided by slow
administration over 20 sec.
We found one prior report of the visualization of duct disruption on
secretin MRCP [16]. That study
compared CT and secretin MRCP in patients with acute pancreatitis. Disruption
was defined as a discontinuity in the duct and was seen in three (8%) of 39
patients. We used a different definition—namely, the visualization of
increasing amounts of fluid outside the duct or proximal small bowel after
secretin stimulation. We preferred this definition because apparent duct
discontinuity in patients with pancreatitis can have a number of causes,
including compression of the duct by fibrosis or edema, strictures, stones, or
adjacent magnetic susceptibility artifacts from gas, hemosiderin, or metal. In
addition, by assessing the change in peripancreatic fluid, one can estimate
the size of the leak.
In conclusion, secretin MRCP is a safe, noninvasive test that shows active
leakage from the pancreatic duct and, thus, pancreatic disruption and can be
used in conjunction with clinical data to select patients for either
interventional or conservative treatment.
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Top
Abstract
Introduction
