DOI:10.2214/AJR.04.1756
AJR 2006; 187:W195-W197
© American Roentgen Ray Society
MR Cholangiopancreatography in the Detection of Symptomatic Ectopic Pancreatitis in the Small-Bowel Mesentery
Alvin C. Silva1,
Joseph C. Charles2,
Brenda D. Kimery2,
Joseph P. Wood3 and
Patrick T. Liu1
1 Department of Diagnostic Radiology, Mayo Clinic, 13400 E Shea Blvd.,
Scottsdale, AZ 85259.
2 Division of Hospital Internal Medicine, Mayo Clinic, Scottsdale, AZ
85259.
3 Department of Emergency Medicine, Mayo Clinic, Scottsdale, AZ 85259.
Received November 12, 2004;
accepted after revision March 15, 2005.
Address correspondence to A. C. Silva.
WEB This is a Web exclusive article.
Keywords: diagnostic imaging • MR cholangiopancreatography • MRI • pancreatic diseases • pancreatitis
Introduction
Ectopic or aberrant pancreas is a rare finding; the estimated incidence is
0.55-13.7% according to autopsy analyses
[1]. Ectopic pancreas within
the mesentery [2] and ectopic
pancreatitis [3] have been
recognized previously as separate findings but have not been documented
concomitantly. Despite diagnostic advances, preoperative noninvasive
evaluation is difficult, and patients have traditionally needed surgical
excision for a definitive diagnosis. We present the case of a 57-year-old
woman with mesenteric ectopic pancreatitis diagnosed using MR
cholangiopancreatography (MRCP) who deferred surgery. To our knowledge, this
is the first report in the English-language medical literature of an MRCP
diagnosis of ectopic pancreatitis.
Case Report
A 57-year-old woman arrived in the emergency department with a 1-day
history of pain in the right side of her back that radiated anteriorly into
the mid epigastric region and into the lower quadrants of the abdomen. The
pain was severe and was associated with nausea. The patient reported having
had a similar episode of pain approximately 1 month before the emergency
visit, but she said that it had resolved with rest without medical attention.
The patient gave a pertinent social history of moderate alcohol intake, having
consumed two to eight alcoholic beverages a day for the past 12 years.
Physical examination revealed mild, generalized abdominal tenderness and
nonspecific guarding. Clinical findings included elevated concentrations of
lipase (649 U/L; reference range, 7-60 U/L) and amylase (175 U/L; reference
range, 30-125 U/L). Findings of liver function tests were within normal
ranges.
The emergency department evaluation included MDCT with IV and enteric
contrast media and rectal air insufflation, according to our standard
diverticulitis protocol. The CT scans revealed an ovoid soft-tissue mass in
the small-bowel mesentery (Fig.
1A). The mass measured 3.7 x 1.7 cm and was located a few
centimeters inferior to the body and tail of the pancreas
(Fig. 1B). The differential
diagnosis included gastrointestinal stromal tumor, carcinoid tumor, and
lymphoma. An inflammatory process involving an ectopic pancreas was also
considered because the patient had an increased concentration of pancreatic
enzymes, but the pancreas proper had no evidence of inflammatory changes
(Fig. 1B). However, the mass
showed enhancement similar to that of the pancreas proper but with surrounding
edematous changes, and there was subtle suggestion of a duct
(Fig. 1A).
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Fig. 1A —57-year-old woman with symptomatic ectopic pancreatitis. CT
scan shows ovoid 3.7 x 1.7 cm soft-tissue mass (short arrows)
in small-bowel mesentery abutting fourth portion of duodenum (D). Surrounding
inflammatory changes and possible duct (long arrow) are evident.
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Fig. 1B —57-year-old woman with symptomatic ectopic pancreatitis. CT
scan obtained a few centimeters superior to A shows body and tail of
pancreas (P) without changes of acute pancreatitis. There was no direct
parenchymal or apparent vascular communication between mass in A and
normal pancreas.
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When the patient declined an immediate operation, MRCP was performed with
heavily T2-weighted, single-shot fast spin-echo, thick- and thin-slab
sequences in the axial and coronal planes after administration of an oral
negative enteric agent and a bowel antimotility agent. Our protocol also
includes axial dual spoiled gradient-echo T1; fat-saturated fast spin-echo T2;
and unenhanced, dynamic, and delayed gadolinium-enhanced gradient-echo T1
sequences dedicated to the pancreas. The MRCP images confirmed the presence of
a duct within the mesenteric mass and allowed us to better define it as
ectopic pancreas rather than any of the other differential considerations
(Figs. 1C and
1D). The duct was found to
drain into the fourth portion of the duodenum, and associated edema of the
parenchyma and surrounding fat was consistent with acute pancreatitis
(Fig. 1E). The ectopic pancreas
was distinctly separate from the pancreas proper, and it showed homogeneous
hyperenhancement without evidence of necrosis
(Fig. 1F). Because of the MRCP
results, the patient was treated conservatively for presumed alcohol-induced
ectopic pancreatitis and was discharged from the hospital after pancreatic
enzyme levels normalized and acute clinical findings resolved.
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Fig. 1C —57-year-old woman with symptomatic ectopic pancreatitis.
Thick-section (C) and thin-section (D) MR
cholangiopancreatograms show ectopic pancreas (arrows, D) and
ectopic duct (ED) distinctly separate from normal pancreas (P, D) and
pancreatic duct (PD, C and D). Use of negative enteric contrast
agent eliminates much of gastrointestinal T2 signal that could have obscured
visualization of ectopic duct.
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Fig. 1D —57-year-old woman with symptomatic ectopic pancreatitis.
Thick-section (C) and thin-section (D) MR
cholangiopancreatograms show ectopic pancreas (arrows, D) and
ectopic duct (ED) distinctly separate from normal pancreas (P, D) and
pancreatic duct (PD, C and D). Use of negative enteric contrast
agent eliminates much of gastrointestinal T2 signal that could have obscured
visualization of ectopic duct.
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Fig. 1E —57-year-old woman with symptomatic ectopic pancreatitis.
Axial single-shot fast spin-echo image shows edema within and surrounding
ectopic pancreas (EP), a finding consistent with acute pancreatitis.
Pancreatic head (P) is normal. CBD = common bile duct; ED = ectopic duct; PD =
pancreatic duct.
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Fig. 1F —57-year-old woman with symptomatic ectopic pancreatitis.
Axial gadolinium-enhanced spoiled gradient-echo T1-weighted image shows
ectopic pancreas (EP) distinctly separate from pancreas proper (P) and
homogeneous hyperenhancement but no evidence of necrosis.
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Discussion
Generally considered a developmental anomaly, ectopic pancreas has been
described as the presence of pancreatic tissue outside the usual location
without anatomic continuity with the main body of the pancreas and with a
distinctly separate ductal system and blood supply
[4]. Most cases of ectopic
pancreas are found in the upper gastrointestinal tract; 70-86.5% of cases
affect the stomach, duodenum, or jejunum
[1,
4]. Other locations include the
gallbladder, bile ducts, splenic hilum, umbilicus, fallopian tubes,
mediastinum, esophagus, lymph nodes, and omentum. Ectopic pancreas also can
occur within a Meckel's diverticulum. The histologic layers involved are, in
descending order of frequency, the submucosa, muscularis propria, and
serosa.
The origin of ectopic pancreatic tissue is controversial. The postulated
theories include possible separation during embryologic rotation and fusion of
the developing pancreatic anlagen; shearing of a lateral bud of the
rudimentary pancreatic duct penetrating the bowel wall, which is then
transported away from the pancreas with subsequent longitudinal intestinal
growth; and differentiation of the totipotent endodermal cells of the
intestinal tract into pancreatic tissue.
Although the reported incidence of ectopic pancreas varies, the true
incidence is not known because the patients often have no symptoms and the
condition usually is an incidental finding at autopsy or laparotomy
[3]. However, any complication
that can occur in the pancreas proper also can occur in ectopic pancreas. Most
complications are caused by mechanical obstruction, but other causes include
cystic degeneration, gastrointestinal bleeding, pancreatic cancer, and acute
pancreatitis [2,
3,
5].
The classic finding on radiographic barium study or at endoscopic
examination is a submucosal mass with central umbilication. Accurate
evaluation is difficult, however. One report cited only one correct
preoperative diagnosis in 17 histologically proven cases of ectopic pancreas
[6]. Another report cited
correct diagnoses in only 5.5% of cases that were initially detected
radiographically [7].
The appearance and enhancement pattern of ectopic pancreas on CT scans have
been reported to be unreliable in differentiating the condition from
gastrointestinal stromal tumor or carcinoid tumor
[8], as was the case with our
patient. The visibility of a subtle duct on our CT scans was biased by the
clinical and laboratory findings and by the surrounding inflammatory changes.
In this patient's case it would otherwise have been difficult to visualize the
presence of a duct on a CT scan because of the tiny caliber of the duct.
Visualization of the duct with MRCP was diagnostic of ectopic pancreas,
obviating histologic confirmation.
In summary, the preoperative diagnosis of ectopic pancreas has
traditionally not been accurate. However, the ability of MRCP to depict an
ectopic duct pathognomonic of ectopic pancreas may preclude the need for
surgical excision to establish a definitive diagnosis in patients with this
challenging condition.
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Introduction
Case Report
