DOI:10.2214/AJR.07.2956
AJR 2009; 192:431-437
© American Roentgen Ray Society
Autoimmune Pancreatitis: Pancreatic and Extrapancreatic Imaging Findings
Kale D. Bodily1,
Naoki Takahashi1,
Joel G. Fletcher1,
Jeff L. Fidler1,
David M. Hough1,
Akira Kawashima1 and
Suresh T. Chari2
1 Department of Radiology, Mayo Clinic, 200 First St. SW, Rochester, MN
55905.
2 Department of Internal Medicine, Division of Gastroenterology, Mayo Clinic,
Rochester, MN.
Received July 30, 2007;
accepted after revision September 3, 2008.
Address correspondence to N. Takahashi
(takahashi.naoki{at}mayo.edu).
Abstract
OBJECTIVE. The purpose of this article is to discuss the systemic
nature of autoimmune pancreatitis and its various pancreatic and
extrapancreatic imaging findings.
CONCLUSION. Autoimmune pancreatitis is a systemic disease with a
wide range of pancreatic and extrapancreatic imaging findings. These findings
can mimic those of other diseases in the pancreas or other organs and
therefore are commonly misdiagnosed and mistreated. It is important for
radiologists to understand both the pancreatic and extrapancreatic imaging
findings of autoimmune pancreatitis to make accurate and timely diagnoses.
Keywords: autoimmune diseases • extrapancreatic findings • pancreas • pancreatitis
Introduction
Autoimmune pancreatitis is an autoimmune systemic disease that involves the
pancreas and several other organ systems, including the bile ducts, the
kidneys, the retroperitoneum, and the salivary glands
[1]. Autoimmune pancreatitis
can sometimes be difficult to differentiate from pancreatic carcinoma, and is
the actual pathology in 2–6% of patients who undergo pancreatic
resection for suspected pancreatic cancer
[2]. Elevation of serum IgG4 is
the best serologic marker. The predominant histologic feature of autoimmune
pancreatitis is infiltration of IgG4-positive lymphocytes into pancreatic or
extrapancreatic tissue. Diagnostic criteria, including clinical, pathologic,
and radiologic features, have been proposed by different groups, including the
Japan Pancreas Society and the Mayo Clinic
[1,
3]. Accurate diagnosis of
autoimmune pancreatitis is particularly important because steroid therapy is
effective and surgery is not necessary.
Typical Pancreatic Findings
Diffuse parenchymal enlargement is a typical feature of autoimmune
pancreatitis that is seen in 40–60% of patients
[4–7].
The pancreatic border becomes featureless with effacement of the lobular
contour of the pancreas [5]
(Figs. 1A and
1B). On CT, there is diffusely
decreased enhancement in the pancreas during the early phase and delayed
enhancement in the late phase of contrast enhancement
[4,
7]. On MRI, the pancreas
appears diffusely hypointense on T1-weighted images, is slightly hyperintense
on T2-weighted images, and exhibits heterogeneously diminished enhancement
during the early phase and delayed enhancement during the late phase of
contrast enhancement [4,
5]
(Fig. 1B). On transabdominal
sonography, diffusely enlarged pancreatic parenchyma becomes hypoechoic
(Fig. 2). On PET, the pancreas
has diffusely increased 18F-FDG uptake
[8]
(Fig. 3).
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Fig. 1A —74-year-old man who has autoimmune pancreatitis with
pancreatic and extrapancreatic involvement. Pancreatic phase contrast-enhanced
axial CT image shows diffuse enlargement and loss of lobulation of pancreas.
Also note intrahepatic bile duct dilatation with enhancement and thickening of
common bile duct (arrowhead) and retroperitoneal fibrosis.
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Fig. 1B —74-year-old man who has autoimmune pancreatitis with
pancreatic and extrapancreatic involvement. T2-weighted axial MR image shows
main pancreatic duct irregularity and focal dilatation. Pancreas is slightly
hyperintense.
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A capsule-like rim, thought to represent inflammatory cell infiltration
[4], can be seen as a halo of
soft-tissue attenuation around the enlarged pancreas in 12–40% of
patients with autoimmune pancreatitis
[5–7].
The rim is low attenuation on contrast-enhanced CT
(Fig. 4A), is hypointense on
both T1- and T2-weighted images, and has delayed enhancement on
contrast-enhanced MRI [4]
(Fig. 4B).
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Fig. 4A —72-year-old man who has autoimmune pancreatitis with
capsule-like pancreatic rim. Contrast-enhanced axial CT image shows diffusely
enlarged pancreas surrounded by capsule-like rim (arrows) of
low-attenuation soft tissue.
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Diffuse or segmental narrowing of the main pancreatic duct is the
characteristic ERCP finding [5]
and a requirement of the Japan Pancreas Society criteria for diagnosis of
autoimmune pancreatitis [1]. MR
cholangiopancreatography (MRCP) can also detect these findings.
Atypical Pancreatic Findings
Focal masslike or segmental enlargement of the pancreas is seen in
30–40% of patients with autoimmune pancreatitis
[5,
7,
9]. On CT, the enlarged segment
of the pancreas is typically isoattenuating or hypoattenuating to the spared,
nonenlarged segment of pancreatic parenchyma
[5] (Figs.
5A,
5B and
6A,
6B) and may be
indistinguishable from pancreatic cancer
[5,
7,
9]. When focal enlargement is
seen, the spared normal-appearing segment may cause biliary dilatation,
suggesting involvement that is not detected on imaging, or may have abnormally
decreased enhancement, which are clues to the diagnosis
[7].
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Fig. 5A —75-year-old man who has autoimmune pancreatitis with
segmental pancreatic involvement. Contrast-enhanced axial CT images were
obtained. CT scans show decreased attenuation, enlargement, and loss of
lobulation of tail of pancreas (arrows, A) and normal
pancreatic head (arrowheads, B).
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Fig. 5B —75-year-old man who has autoimmune pancreatitis with
segmental pancreatic involvement. Contrast-enhanced axial CT images were
obtained. CT scans show decreased attenuation, enlargement, and loss of
lobulation of tail of pancreas (arrows, A) and normal
pancreatic head (arrowheads, B).
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Fig. 6A —80-year-old man with autoimmune pancreatitis mimicking
pancreatic cancer. Contrast-enhanced axial CT images were obtained. Image
shows ill-defined, slightly low-attenuation area in head of pancreas
(arrowheads).
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Fig. 6B —80-year-old man with autoimmune pancreatitis mimicking
pancreatic cancer. Contrast-enhanced axial CT images were obtained.
Abnormality in head of pancreas results in dilatation of pancreatic duct in
body and tail with abrupt cutoff. This patient underwent steroid therapy after
biopsy.
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Normal or atrophic pancreatic parenchyma can be seen in 5–20% of
patients, likely representing a late burnt-out phase of the disease
[5,
7]. This appearance can also be
seen after steroid therapy.
Extrapancreatic Findings
Autoimmune pancreatitis has many extrapancreatic manifestations, most
commonly biliary, renal, and retroperitoneal. It is important for the
radiologist to be facile with the extrapancreatic findings of autoimmune
pancreatitis because these findings can be diagnostic when the pancreatic
findings of autoimmune pancreatitis are atypical.
Biliary Involvement
Biliary involvement is seen in up to 80% of patients with autoimmune
pancreatitis [5,
10]. This is the most common
form of extrapancreatic involvement and can occur in the absence of pancreatic
findings. Both intrahepatic and extrahepatic bile ducts can be involved, with
the lower common bile duct being the most usual area of involvement.
Multifocal intrahepatic or upper extrahepatic bile duct strictures or bile
duct thickening and enhancement resembling primary sclerosing cholangitis are
present in 10–35% of patients. Biliary involvement is best evaluated by
ERCP or MRCP [11] (Fig.
7A,
7B). On CT, biliary
involvement may appear as focal or diffuse thickening and enhancement of the
bile duct wall [6,
7]
(Figs. 1A). Rarely, a
soft-tissue mass develops that can resemble cholangiocarcinoma (Fig.
8A,
8B). Gallbladder involvement
is also common and appears as diffuse thickening of the gallbladder wall.
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Fig. 7A —69-year-old man who has autoimmune pancreatitis with biliary
involvement. (Reprinted with permission from
[3]) ERCP image shows multiple
focal areas of stricture and dilation in intrahepatic bile ducts that are
similar in appearance to primary sclerosing cholangitis.
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Fig. 7B —69-year-old man who has autoimmune pancreatitis with biliary
involvement. (Reprinted with permission from
[3]) After steroid therapy,
ERCP image shows biliary abnormalities have resolved to near normal.
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Fig. 8A —75-year-old man who has autoimmune pancreatitis with masslike
biliary involvement. Gadolinium-enhanced axial fat-saturated T1-weighted 3D
fast spoiled gradient-recalled echo axial MR image shows ill-defined masslike
soft-tissue lesion at confluence of intrahepatic bile ducts
(arrowheads).
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Fig. 8B —75-year-old man who has autoimmune pancreatitis with masslike
biliary involvement. MR cholangiopancreatography image using thick-slab
heavily T2-weighted single-shot fast spin echo shows narrowing of bile ducts
at hilum. This is a less common form of biliary involvement in autoimmune
pancreatitis, and appearance is particularly difficult to differentiate from
cholangiocarcinoma.
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Renal Involvement
Renal involvement is present in about 35% of patients with autoimmune
pancreatitis, with renal parenchyma involvement in 30% and renal sinus or
renal pelvis wall involvement in 10%
[12]. Renal parenchymal
lesions are often bilateral and multiple, predominantly involve the renal
cortex, and can be categorized into four patterns: well-defined or ill-defined
round lesions (Fig. 9),
well-circumscribed wedge-shaped lesions
(Fig. 10), small peripheral
cortical nodules (Fig. 1C), and
diffuse patchy involvement (Fig.
11). Other unusual renal parenchymal manifestations include a
large solitary mass (Fig. 12).
The lesions are low attenuation during the pancreatic phase of enhancement and
gradually enhance in the later phase. On MRI, the lesions appear isointense on
T1-weighted images and hypointense on T2-weighted images, and have gradual
enhancement after contrast administration.
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Fig. 10 —53-year-old man who has autoimmune pancreatitis with renal
involvement. Contrast-enhanced axial CT image shows large wedge-shaped
low-attenuation lesion in left kidney. Also note small wedge-shaped
low-attenuation lesion in right kidney (arrowhead).
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Fig. 1C —74-year-old man who has autoimmune pancreatitis with
pancreatic and extrapancreatic involvement. Corticomedullary phase
contrast-enhanced axial CT image shows multiple small low-attenuation cortical
nodules in both kidneys (arrows). Note periaortic halo of soft-tissue
attenuation surrounding abdominal aorta, indicative of retroperitoneal
fibrosis. This resulted in partial obstruction of left ureter.
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Fig. 12 —62-year-old man who has autoimmune pancreatitis with renal
involvement. Contrast-enhanced axial CT image shows exophytic solid mass
arising from left kidney. Surgical pathology confirmed IgG4-positive
lymphoplasmacytic infiltration.
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Retroperitoneal Involvement
Retroperitoneal fibrosis, which manifests as a soft-tissue mass surrounding
the abdominal aorta and inferior vena cava
(Fig. 1C), is seen in
approximately 10% of patients
[5,
7].
Salivary Gland Involvement
Salivary gland enlargement is seen in 15% of patients with autoimmune
pancreatitis [13]. Salivary
gland dysfunction clinically similar to Sjögren's syndrome can also be
seen in long-standing autoimmune pancreatitis.
Other Organ Involvement
Lymphadenopathy is not rare; abdominal lymphadenopathy was observed in more
than half of patients who underwent laparotomy for autoimmune pancreatitis in
one report [10]. Cervical or
mediastinal lymphadenopathy can be also seen
[5]
(Fig. 13A). Pulmonary
involvement has been reported in association with autoimmune pancreatitis,
manifesting as reticular or ground-glass interstitial opacities or irregular
nodules on CT [14]
(Fig. 13B). Involvement of the
gastrointestinal tract, including the stomach, has been reported, which causes
gastric wall thickening and ulcer formation
[15]
(Fig. 14).
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Fig. 13B —77-year-old man who has autoimmune pancreatitis with lung and
lymph node involvement. Contrast-enhanced axial CT images were obtained.
Interstitial infiltration is seen on the right, predominantly around
bronchovascular bundles. Note right pleural effusion. Surgical pathology
confirmed IgG4-positive lymphoplasmacytic infiltration.
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Fig. 14 —35-year-old man who has autoimmune pancreatitis with gastric
involvement. Contrast-enhanced axial CT image shows diffuse thickening of
gastric wall that is most marked in antrum. Endoscopic biopsy confirmed
diagnosis. Note mild enlargement of pancreas.
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Conclusion
Autoimmune pancreatitis has variable multisystem involvement with
characteristic imaging findings that have only recently been described.
Multitechnique pancreatic imaging findings of autoimmune pancreatitis can be
divided into typical findings and atypical findings. Typical pancreatic
findings include diffuse parenchymal enlargement with a feature less border, a
capsule-like rim, and diffuse narrowing of the pancreatic duct. Atypical
pancreatic findings include focal masslike enlargement of the pancreas and
atrophy of the pancreas. The most commonly involved organs outside the
pancreas are the biliary ductal system, the kidneys, the retroperitoneum, and
the salivary glands. Involvement of various other organs has been reported.
Differentiating autoimmune pancreatitis from malignancy remains the primary
diagnostic challenge.
References
- Okazaki K, Kawa S, Kamisawa T, et al. Clinical diagnostic criteria
of autoimmune pancreatitis: revised proposal. J
Gastroenterol 2006; 41:626
–631[CrossRef][Medline]
- Yadav D, Notahara K, Smyrk TC, et al. Idiopathic tumefactive
chronic pancreatitis: clinical profile, histology, and natural history after
resection. Clin Gastroenterol Hepatol2003; 1:129
–135[CrossRef][Medline]
- Chari ST, Smyrk TC, Levy MJ, et al. Diagnosis of autoimmune
pancreatitis: the Mayo Clinic experience. Clin Gastroenterol
Hepatol 2006; 4:1010
–1016[CrossRef][Medline]
- Irie H, Honda H, Baba S, et al. Autoimmune pancreatitis: CT and MR
characteristics. AJR 1998;170
:1323
–1327[Abstract/Free Full Text]
- Sahani DV, Kalva SP, Farrell J, et al. Autoimmune pancreatitis:
imaging features. Radiology 2004;233
: 345–352[Abstract/Free Full Text]
- Yang DH, Kim KW, Kim TK, et al. Autoimmune pancreatitis: radiologic
findings in 20 patients. Abdom Imaging2006; 31:94
–102[CrossRef][Medline]
- Takahashi N, Fletcher JG, Fidler JL, Hough DM, Kawashima A, Chari
ST. Dual-phase CT of autoimmune pancreatitis: a multireader study.
AJR 2008; 190:280
–286[Abstract/Free Full Text]
- Nakamoto Y, Saga T, Ishimori T, et al. FDG-PET of
autoimmune-related pancreatitis: preliminary results. Eur J Nucl
Med 2000; 27:1835
–1838[CrossRef][Medline]
- Wakabayashi T, Kawaura Y, Satomura Y, et al. Clinical and imaging
features of autoimmune pancreatitis with focal pancreatic swelling or mass
formation: comparison with so-called tumor-forming pancreatitis and pancreatic
carcinoma. Am J Gastroenterol 2003;98
:2679
–2687[CrossRef][Medline]
- Kamisawa T, Egawa N, Nakajima H, Tsuruta K, Okamoto A.
Extrapancreatic lesions in autoimmune pancreatitis. J Clin
Gastroenterol 2005; 39:904
–907[CrossRef][Medline]
- Nakazawa T, Ohara H, Sano H, et al. Cholangiography can
discriminate sclerosing cholangitis with autoimmune pancreatitis from primary
sclerosing cholangitis. Gastrointest Endosc2004; 60:937
–944[CrossRef][Medline]
- Takahashi N, Kawashima A, Fletcher JG, Chari ST. Renal involvement
in patients with autoimmune pancreatitis: CT and MR imaging findings.
Radiology 2007;242
: 791–801[Abstract/Free Full Text]
- Kamisawa T, Tu Y, Egawa N, Sakaki N, Inokuma S, Kamata N. Salivary
gland involvement in chronic pancreatitis of various etiologies. Am
J Gastroenterol 2003; 98:323
–326[CrossRef][Medline]
- Hirano K, Kawabe T, Komatsu Y, et al. High-rate pulmonary
involvement in autoimmune pancreatitis. Intern Med J2006; 36:58
–61[CrossRef][Medline]
- Shinji A, Sano K, Hamano H, et al. Autoimmune pancreatitis is
closely associated with gastric ulcer presenting with abundant IgG4-bearing
plasma cell infiltration. Gastrointest Endosc2004; 59:506
–511[CrossRef][Medline]
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Abstract
Introduction
