Autoimmune pancreatitis: CT and MR characteristics

Prevalence and clinicopathological features of autoimmune pancreatitis in Japanese patients with inflammatory bowel disease

OBJECTIVES

The purpose of this study was to clarify the clinicopathological characteristics of autoimmune pancreatitis (AIP) in Japanese patients with inflammatory bowel disease (IBD).

METHODS

The clinicopathological findings of 7 patients with IBD whose definite AIP was diagnosed in our hospital according to the International Consensus Diagnostic Criteria were reviewed.

RESULTS

Five (0.5%) of 961 patients with ulcerative colitis (UC) and 2 (0.3%) of 790 patients with Crohn disease had AIP. All of 7 patients whose AIP was diagnosed were type 2. The rate of elevated values of serum immunoglobulin G4 was 0%. Most patients with the diagnosis of IBD preceded that of AIP, and disease activity of IBD were active. Granulocyte epithelial lesion is similar to the cryptitis seen in colonic tissue of UC. All of 7 patients were given corticosteroids, immunomodulators, and/or biological agents for IBD. One patient had a recurrence.

CONCLUSIONS

The frequency of AIP in Japanese patients with IBD was low. All cases were type 2 and responded well to corticosteroids, immunomodulators, and biological agents. Autoimmune pancreatitis in UC patients may be an extraintestinal manifestation of UC.

IgG4-related disease: dataset of 235 consecutive patients

Immunoglobulin G4-related disease (IgG4-RD) is a recently discovered systemic condition, in which various organ manifestations are linked by a similar histological appearance. Our knowledge of this condition is still fragmented, as most studies have examined only a few dozen patients or focused on a particular organ manifestation. This study was conducted to learn the demography and patient characteristics of IgG4-RD using a large cohort. A total of 235 consecutive patients with IgG4-RD, diagnosed in 8 general hospitals in the same medical district, were identified by searching the institutions' radiology database. Inclusion criteria were histology-proven IgG4-RD according to the Pathology Consensus Statement and/or definitive type 1 autoimmune pancreatitis meeting the International Consensus Diagnostic Criteria. Clinical notes and images of selected patients were retrospectively reviewed. All patients were adults (M/F = 4/1). The median age was 67 years (range 35-86). Nine tenths were diagnosed in their 50s to 70s. Among 486 manifestations identified in total, the most common was pancreatitis diagnosed in 142 patients (60%), followed by sialadenitis (34%), tubulointerstitial nephritis (23%), dacryoadenitis (23%), and periaortitis (20%). The majority of patients (95%) had at least 1 of the 5 most common manifestations. Male and female patients differed in their organ manifestations (periaortitis more common in males and sialodacryoadenitis more common in females). Serum IgG4 (normal ≤135 mg/dL) was elevated to >135 mg/dL in 208 patients (88%) and >270 mg/dL in 167 (71%). The IgG4 value was significantly higher in patients with multiorgan involvement than in those with a single manifestation (median 629 mg/dL vs 299 mg/dL, P < 0.01). Of 218 patients, for whom both IgG4 and IgG values were available, the IgG4/IgG ratio was raised to >10% in 194 (89%). Corticosteroids were effective, but the relapse rate was estimated to be 24% in the study period (median 37 months). During the follow-up, 15 malignant diseases were diagnosed in 13 patients (6%). This figure is similar to the incidence (12.9 cancers) expected from the Japanese nationwide study for cancer epidemiology (standardized incidence ratio 1.16). In conclusion, this reliable dataset could improve the characterization of IgG4-RD, particularly its unique demography and the frequency of each organ manifestation.

CT and MRI Findings of Autoimmune Polymorph Bifocal Pancreatitis Mimicking Pancreatic Adenocarcinoma: A Case Report and Review of the Literature

Autoimmune pancreatitis is a rare type of chronic pancreatitis. It is supposed to be a pancreatic manifestation of an immune-complex modulated systemic disorder. In contrast, pancreatic adenocarcinoma is the most frequent malignant neoplasm of the pancreas. Within the rare type of focal autoimmune pancreatitis, only few presentations with multifocal pancreatic lesions have been described. Herein we report a case of a 58-year-old patient with autoimmune pancreatitis presenting with bifocal manifestations of the pancreatic head and tail, mimicking pancreatic adenocarcinoma clinically, on computed tomography and magnetic resonance imaging. Typical imaging findings of autoimmune pancreatitis are compared with typical findings in pancreatic carcinoma. The diagnostic dilemma of differentiating between both entities is discussed. A review of the present literature regarding multifocal presence of autoimmune pancreatitis is performed.

Pancreatic duct abnormalities in focal autoimmune pancreatitis: MR/MRCP imaging findings

AIM

To evaluate the magnetic resonance (MR) imaging-MR cholangiopancreatographic (MRCP) findings of focal forms of autoimmune pancreatitis (AIP) to describe ductal involvement at diagnosis.

METHODS

MR examinations of 123 patients affected by AIP were analysed. We included 26 patients who satisfied International Consensus Diagnostic Criteria and were suffering from focal AIP. Image analysis included: site of parenchymal enlargement, main pancreatic duct (MPD) diameter, MPD stenosis, stricture length, presence of upstream dilation within the stricture, signal intensity, and pancreatic enhancement.

RESULTS

Signal intensity abnormalities were localized in the head in 10/26 (38.5%) and in the body-tail in 16/26 (61.5%) patients. MRCP showed a single MPD stenosis in 12/26 (46.1%) and multiple MPD stenosis in 14/26 (53.8%) patients, without a dilation of the upstream MPD (mean: 3.83 mm). Lesions showed hypointensity on T1-weighted images in all patients, and hyperintensity on T2-weighted images in 22/26 (84.6%) patients. The affected parenchyma was hypovascular during the arterial phase in 25/26 (96.2%) patients with contrast retention.

CONCLUSIONS

MR-MRCP are effective techniques for the diagnosis of AIP showing the loss of the physiological lobulation and the typical contrastographic appearance. The presence of multiple, long stenoses without an upstream MPD dilation at MRCP suggests the diagnosis of AIP, and can be useful in differential diagnosis of pancreatic adenocarcinoma.

KEY POINTS

• MRI represents the gold standard in the diagnosis of AIP. • MRCP is an increasingly useful technique in the diagnosis of focal AIP. • MRCP could be a problem-solving tool in the differential diagnosis of AIP.

Pancreatic duct "Icicle sign" on MRI for distinguishing autoimmune pancreatitis from pancreatic ductal adenocarcinoma in the proximal pancreas

OBJECTIVE

To determine reliable MRI features of autoimmune pancreatitis (AIP) in the proximal pancreas that could allow its differentiation from pancreatic ductal adenocarcinoma (PDAC).

METHODS

Twenty-three patients with AIP and 61 patients with PDAC in the proximal pancreas underwent MRI. Two observers analyzed MRI for lesion morphology, hypointensity degree on T1-weighted images, enhancement pattern during dynamic phases, capsule-like rim, presence of cysts and duct penetrating sign, morphology of bile duct, and icicle appearance and tortuosity of the upstream pancreatic duct. Sensitivity and specificity for the diagnosis of AIP were calculated for each category or combined.

RESULTS

When isointensity on the portal and late phase of MRI and/or the icicle sign of pancreatic duct are applied, 100 % sensitivity for the diagnosis of AIP in the proximal pancreas was achieved. Applying both mild T1 hypointensity similar to the spleen and the icicle sign enabled 100 % specificity for the diagnosis of AIP by differentiating it from PDAC.

CONCLUSION

The combination of the icicle sign in the upstream pancreatic duct and mild T1 hypointensity or isointensity on portal and late phase of dynamic MRI could be reliable MR features for the diagnosis of AIP in the proximal pancreas by allowing its differentiation from PDAC.

KEY POINTS

• The icicle sign of the pancreatic duct is useful for diagnosing AIP. • Mild T1 hypointensity similar to the spleen is useful for diagnosing AIP. • Isointensity on portal and late phases MRI is useful for diagnosing AIP.

Diagnosis of autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a distinct form of chronic pancreatitis that is increasingly being reported. The presentation and clinical image findings of AIP sometimes resemble those of several pancreatic malignancies, but the therapeutic strategy differs appreciably. Therefore, accurate diagnosis is necessary for cases of AIP. To date, AIP is classified into two distinct subtypes from the viewpoints of etiology, serum markers, histology, other organ involvements, and frequency of relapse: type 1 is related to IgG4 (lymphoplasmacytic sclerosing pancreatitis) and type 2 is related to a granulocytic epithelial lesion (idiopathic duct-centric chronic pancreatitis). Both types of AIP are characterized by focal or diffuse pancreatic enlargement accompanied with a narrowing of the main pancreatic duct, and both show dramatic responses to corticosteroid. Unlike type 2, type 1 is characteristically associated with increasing levels of serum IgG4 and positive serum autoantibodies, abundant infiltration of IgG4-positive plasmacytes, frequent extrapancreatic lesions, and relapse. These findings have led several countries to propose diagnostic criteria for AIP, which consist of essentially similar diagnostic items; however, several differences exist for each country, mainly due to differences in the definition of AIP and the modalities used to diagnose this disease. An attempt to unite the diagnostic criteria worldwide was made with the publication in 2011 of the international consensus diagnostic criteria for AIP, established at the 2010 Congress of the International Association of Pancreatology (IAP).

Autoimmune pancreatitis in the context of IgG4-related disease: Review of imaging findings

Current understanding of autoimmune pancreatitis (AIP) recognizes a histopathological subtype of the disease to fall within the spectrum of IgG4-related disease. Along with clinical, laboratory, and histopathological data, imaging plays an important role in the diagnosis and management of AIP, and more broadly, within the spectrum of IgG4-related disease. In addition to the defined role of imaging in consensus diagnostic protocols, an array of imaging modalities can provide complementary data to address specific clinical concerns. These include contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging for pancreatic parenchymal lesion localization and characterization, endoscopic retrograde and magnetic resonance cholangiopancreatography (ERCP and MRCP) to assess for duct involvement, and more recently, positron emission tomography (PET) imaging to assess for extra-pancreatic sites of involvement. While the imaging appearance of AIP varies widely, certain imaging features are more likely to represent AIP than alternate diagnoses, such as pancreatic cancer. While nonspecific, imaging findings which favor a diagnosis of AIP rather than pancreatic cancer include: delayed enhancement of affected pancreas, mild dilatation of the main pancreatic duct over a long segment, the “capsule” and “penetrating duct” signs, and responsiveness to corticosteroid therapy. Systemic, extra-pancreatic sites of involvement are also often seen in AIP and IgG4-related disease, and typically respond to corticosteroid therapy. Imaging by CT, MR, and PET also play a role in the diagnosis and monitoring after treatment of involved sites.

Magnetic resonance imaging of pancreatitis: An update

Magnetic resonance (MR) imaging plays an important role in the diagnosis and staging of acute and chronic pancreatitis and may represent the best imaging technique in the setting of pancreatitis due to its unmatched soft tissue contrast resolution as well as non-ionizing nature and higher safety profile of intravascular contrast media, making it particularly valuable in radiosensitive populations such as pregnant patients, and patients with recurrent pancreatitis requiring multiple follow-up examinations. Additional advantages include the ability to detect early forms of chronic pancreatitis and to better differentiate adenocarcinoma from focal chronic pancreatitis. This review addresses new trends in clinical pancreatic MR imaging emphasizing its role in imaging all types of acute and chronic pancreatitis, pancreatitis complications and other important differential diagnoses that mimic pancreatitis.

Pancreatitis-imaging approach

Pancreatitis is defined as the inflammation of the pancreas and considered the most common pancreatic disease in children and adults. Imaging plays a significant role in the diagnosis, severity assessment, recognition of complications and guiding therapeutic interventions. In the setting of pancreatitis, wider availability and good image quality make multi-detector contrast-enhanced computed tomography (MD-CECT) the most used imaging technique. However, magnetic resonance imaging (MRI) offers diagnostic capabilities similar to those of CT, with additional intrinsic advantages including lack of ionizing radiation and exquisite soft tissue characterization. This article reviews the proposed definitions of revised Atlanta classification for acute pancreatitis, illustrates a wide range of morphologic pancreatic parenchymal and associated peripancreatic changes for different types of acute pancreatitis. It also describes the spectrum of early and late chronic pancreatitis imaging findings and illustrates some of the less common types of chronic pancreatitis, with special emphasis on the role of CT and MRI.

Isolated IgG4-related sclerosing cholangitis: a report of 9 cases

Extrahepatic bile ducts are the most commonly involved extrapancreatic organ site in patients with type 1 autoimmune pancreatitis. IgG4-related sclerosing cholangitis (IgG4-SC) alone, without evidence of pancreatic or other organ involvement, is uncommon and is difficult to distinguish from cholangiocarcinoma preoperatively. We describe 9 patients with isolated IgG4-SC over an approximate 10-year period, each clinically suspected to have cholangiocarcinoma. We examined the clinical, radiological, cytologic (including fluorescence in situ hybridization results), and histologic features. IgG and IgG4 immunohistochemistry were performed. All 9 patients were middle-aged men who presented with obstructive jaundice. The biliary strictures involved all parts of the extrahepatic biliary tree. Serum IgG4 was slightly elevated in three of eight patients. Cytologic findings were interpreted as negative in six, atypical in one, and suspicious for adenocarcinoma in one. Fluorescence in situ hybridization revealed aneuploidy in one and was equivocal (trisomy 7) in 2. Eight of 9 patients underwent radical resection for suspected cholangiocarcinoma. There was only one case diagnosed with IgG4-SC preoperatively based on biopsy. Histologic sections revealed a prominent lymphoplasmacytic infiltrate with storiform fibrosis and marked increased IgG4-positive plasma cells (≥30/high-power field) in all specimens. Fifty percent of cases (4/8) had IgG4/IgG plasma cell ratio >40%. On median follow-up of 2.8 years, no relapse has occurred in any patient. Extrahepatic IgG4-SC may present as an isolated lesion mimicking cholangiocarcinoma. The diagnosis can be challenging. Clinicians and pathologists should recognize this to avoid major surgery.

Amendment of the Japanese Consensus Guidelines for Autoimmune Pancreatitis, 2013 I. Concept and diagnosis of autoimmune pancreatitis

BACKGROUND

In response to the proposal of the international consensus diagnostic criteria (ICDC) for autoimmune pancreatitis (AIP) and the Japanese diagnostic criteria in 2011, the 2009 Japanese consensus guidelines for managing AIP required revision.

METHODS

Three committees [the professional committee for making clinical questions (CQs) and statements by Japanese specialists, the expert panelist committee for rating statements by the modified Delphi method, and the evaluating committee by moderators] were organized. Fifteen specialists for AIP extracted the specific clinical statements from 1,843 articles published between 1963 and 2012 (obtained from Pub Med and a secondary database, and developed the CQs and statements. The expert panel individually rated the clinical statements using a modified Delphi approach, in which a clinical statement receiving a median score greater than seven on a nine-point scale from the panel was regarded as valid.

RESULTS

The professional committee created 13 CQs and statements for the current concept and diagnosis of AIP, 6 for extra-pancreatic lesions, 6 for differential diagnosis, and 11 for treatment.

CONCLUSION

After evaluation by the moderators, amendments to the Japanese consensus guidelines for AIP have been proposed for 2013.

Autoimmune pancreatitis: multidetector-row computed tomography (MDCT) and magnetic resonance (MR) findings in the Italian experience

Multidetector-row computed tomography (MDCT) and magnetic resonance (MR) imaging are currently the most frequently performed imaging modalities for the study of pancreatic disease. In cases of suspected autoimmune pancreatitis (AIP), a dynamic quadriphasic (precontrast, contrast-enhanced pancreatic, venous and late phases) study is recommended in both techniques. In the diffuse form of autoimmune pancreatitis (DAIP), the pancreatic parenchyma shows diffuse enlargement and appears, during the MDCT and MR contrast-enhanced pancreatic phase, diffusely hypodense and hypointense, respectively, compared to the spleen because of lymphoplasmacytic infiltration and pancreatic fibrosis. During the venous phase of MDCT and MR imaging, the parenchyma appears hyperdense and hyperintense, respectively, in comparison to the pancreatic phase. In the delayed phase of both imaging modalities, it shows retention of contrast media. A "capsule-like rim" may be recognised as a peripancreatic MDCT hyperdense and MR hypointense halo in the T2-weighted images, compared to the parenchyma. DAIP must be differentiated from non-necrotizing acute pancreatitis (NNAP) and lymphoma since both diseases show diffuse enlargement of the pancreatic parenchyma. The differential diagnosis is clinically difficult, and dynamic contrast-enhanced MDCT has an important role. In the focal form of autoimmune pancreatitis (FAIP), the parenchyma shows segmental enlargement involving the head, the body-tail or the tail, with the same contrast pattern as the diffuse form on both modalities. FAIP needs to be differentiated from pancreatic adenocarcinoma to avoid unnecessary surgical procedures, since both diseases have similar clinical and imaging presentation. The differential diagnosis is clinically difficult, and dynamic contrast-enhanced MDCT and MR imaging both have an important role. MR cholangiopancreatography helps in the differential diagnosis. Furthermore, MDCT and MR imaging can identify the extrapancreatic manifestations of AIP, most commonly biliary, renal and retroperitoneal. Finally, in all cases of uncertain diagnosis, MDCT and/or MR follow-up after short-term treatment (2-3 weeks) with high-dose steroids can identify a significant reduction in size of the pancreatic parenchyma and, in FAIP, normalisation of the calibre of the upstream main pancreatic duct.

Serum protein signatures differentiating autoimmune pancreatitis versus pancreatic cancer

Autoimmune pancreatitis (AIP) is defined by characteristic lymphoplasmacytic infiltrate, ductal strictures and a pancreatic enlargement or mass that can mimic pancreatic cancer (PaCa). The distinction between this benign disease and pancreatic cancer can be challenging. However, an accurate diagnosis may pre-empt the misdiagnosis of cancer, allowing the appropriate medical treatment of AIP and, consequently, decreasing the number of unnecessary pancreatic resections.

Mass spectrometry (MS) and two-dimensional differential gel electrophoresis (2D-DIGE) have been applied to analyse serum protein alterations associated with AIP and PaCa, and to identify protein signatures indicative of the diseases. Patients' sera were immunodepleted from the 20 most prominent serum proteins prior to further 2D-DIGE and image analysis. The identity of the most-discriminatory proteins detected, was performed by MS and ELISAs were applied to confirm their expression. Serum profiling data analysis with 2D-DIGE revealed 39 protein peaks able to discriminate between AIP and PaCa. Proteins were purified and further analysed by MALDI-TOF-MS. Peptide mass fingerprinting led to identification of eleven proteins. Among them apolipoprotein A-I, apolipoprotein A-II, transthyretin, and tetranectin were identified and found as 3.0-, 3.5-, 2-, and 1.6-fold decreased in PaCa sera, respectively, whereas haptoglobin and apolipoprotein E were found to be 3.8- and 1.6-fold elevated in PaCa sera. With the exception of haptoglobin the ELISA results of the identified proteins confirmed the 2D-DIGE image analysis characteristics. Integration of the identified serum proteins as AIP markers may have considerable potential to provide additional information for the diagnosis of AIP to choose the appropriate treatment.

Mechanisms and assessment of IgG4-related disease: lessons for the rheumatologist

Recognition of IgG4-related disease as an independent chronic inflammatory disorder is a relatively new concept; previously, the condition was thought to represent a subtype of Sjögren's syndrome. IgG4-related disease is characterized by elevated serum levels of IgG4 and inflammation of various organs, with abundant infiltration of IgG4-bearing plasma cells, storiform fibrosis and obliterative phlebitis representing the major histopathological features of the swollen organs. The aetiology and pathogenesis of this disorder remain unclear, but inflammation and subsequent fibrosis occur due to excess production of type 2 T-helper-cell and regulatory T-cell cytokines. The disease can comprise various organ manifestations, such as dacryoadenitis and sialadenitis (also called Mikulicz disease), type 1 autoimmune pancreatitis, kidney dysfunction and lung disease. Early intervention using glucocorticoids can improve IgG4-related organ dysfunction; however, patients often relapse when doses of these agents are tapered. The disease has also been associated with an increased incidence of certain malignancies. Increased awareness of IgG4-related disease might lead to consultation with rheumatologists owing to its clinical, and potentially pathogenetic, similarities with certain rheumatic disorders. With this in mind, we describe the pathogenic mechanisms of IgG4-related disease, and outline considerations for diagnosis and treatment of the condition.

DWI findings of autoimmune pancreatitis: comparison between symptomatic and asymptomatic patients

PURPOSE

To compare the MR findings including diffusion-weighted imaging (DWI) between symptomatic and asymptomatic patients with autoimmune pancreatitis (AIP) and to determine whether DWI can be used as an objective biomarker for symptomatic AIP, which is considered an indication for steroid therapy.

MATERIALS AND METHODS

This retrospective study was approved by our institutional review board. MRI scans from 37 patients with AIP (symptomatic, n = 19; asymptomatic, n = 18) were retrospectively evaluated. The imaging studies were performed on a 1.5 Tesla scanner and assessed for parenchymal enlargement, narrowing of the main pancreatic duct, hypointensity on fat-suppressed T1-weighted images (FS-T1WI), a capsule-like rim, extrapancreatic lesions, and hyperintensity on DWI. The findings were compared by univariate and multivariate logistic regression analysis. Apparent diffusion coefficient (ADC) values were also calculated.

RESULTS

Multivariate analysis showed that hyperintensity on DWI were most significantly associated with the symptoms of AIP (odds ratio = 28.2; P = 0.003). Interobserver agreement for DWI was also high. The ADC values were significantly lower in symptomatic than in asymptomatic patients (0.94 ± 0.17 versus 1.16 ± 0.16 × 10(-3) mm(2)/s, P < 0.001). Receiver operating characteristic curve analysis of the ADC values to differentiate between symptomatic and asymptomatic patients showed that sensitivity was 68.4%, specificity 83.3%, and AUC 0.74.

CONCLUSION

Signal intensity on DWI and ADC value were well correlated with the active symptoms of AIP patients. DWI may be useful as an objective biomarker for determining the indication for steroid therapy.

Clinics in diagnostic imaging. 145

A 63-year-old man presented with painless jaundice, loss of appetite and significant weight loss. Cross-sectional imaging showed a diffusely enlarged pancreas, with no significant fat stranding and a hypodense rim on computed tomography, which appeared hypointense on T2-weighted magnetic resonance imaging. There was a narrowed pancreatic duct and features of common bile duct narrowing in the region of the pancreatic head. However, there was no obvious mass seen in the pancreatic head region. These features were classical of autoimmune pancreatitis with diffuse involvement of the gland. Laboratory investigation showed abnormal liver function and the classical sign of raised immunoglobulin G class 4 antibodies. The patient showed dramatic response to high-dose steroids, with resolution of both the laboratory and imaging abnormalities within one month. We discuss the classical imaging features of Type 1 autoimmune pancreatitis, an uncommon condition that needs to be differentiated from pancreatic malignancy.

Multifocal lesions with pancreatic atrophy in IgG4-related autoimmune pancreatitis: report of a case

We herein report a case of IgG4-related autoimmune pancreatitis (AIP). A 72-year-old male with jaundice visited our hospital complaining of epigastralgia. A blood chemistry analysis revealed elevated serum levels of total bilirubin and DUPAN-II. Computed tomography (CT) revealed irregularly shaped pancreatic masses with a stricture of the main pancreatic duct (MPD) in the head and tail that were interposed by marked atrophy with MPD dilation in the body. F-18 fluorodeoxyglucose (FDG)-positron emission tomography/CT revealed abnormally intense FDG uptake only at the masses. During surgery, another small tumor was also found in the atrophied body; therefore, a total pancreatectomy was performed under the diagnosis of multiple pancreatic cancers. The histological analysis revealed fibrosis with dense and diffuse infiltrations of lymphocytes and IgG4-positive plasma cells. The pancreatic parenchyma of the body was firmly replaced by fibrosis. AIP can lead to the formation of multiple pancreatic lesions, and thus the correct diagnosis is occasionally difficult to establish in atypical cases.

MRI of the pancreas: problem solving tool

Advances in MR hardware and pulse sequence design over the years have improved the quality and robustness of MR imaging of the pancreas. Today, MRI is an indispensible tool for studying the pancreas and can provide useful information not attainable with other noninvasive or minimally invasive imaging techniques. In the present review, specific cases are reviewed where the strengths of MRI demonstrate the utility of this imaging modality as a problem solving tool.

MR features of primary and secondary malignant lymphoma of the pancreas: a pictorial review

OBJECTIVE

To describe the imaging findings of primary and secondary pancreatic malignant lymphoma on magnetic resonance imaging (MRI), to help differentiate lymphoma of the pancreas from primary adenocarcinoma and autoimmune pancreatitis among others, and to discuss a few atypical presentations of pancreatitis mimicking lymphoma.

CONCLUSION

Knowledge of these imaging manifestations of lymphoma may be helpful to arrive at an accurate diagnosis and avoid unnecessary morbidity and mortality from inadvertent surgery.

MAIN MESSAGES

• Pancreatic malignant lymphoma is shown as a nodular low-density area with mild enhancement on CT. • It sometimes shows variable manifestations mimicking other tumours and inflammatory conditions. • MRI provides useful information for differentiating malignant lymphoma from other mimickers.

Imaging of focal autoimmune pancreatitis and differentiating it from pancreatic cancer

Autoimmune pancreatitis (AIP) is an inflammatory disorder of pancreas. Two types have been identified: the diffuse and the focal or mass forming. Clinical presentation of AIP overlaps that of pancreatic cancer (PC). Sometimes serum IgG4 and CA 19-9 levels are unable to differentiate AIP from PC. Various series have shown that 5%–21% of resected pancreatic masses for suspected malignancy turned out to be AIP. Accurate diagnosis of focal AIP can avoid unnecessary surgeries. This paper elaborates the various imaging modalities useful in differentiating focal AIP from PC.

Immunoglobulin G4-related sclerosing cholangitis: pathologic features and histologic mimics

Since immunoglobulin G4 (IgG4)-related sclerosing cholangitis was first described in 2004, this condition has been recognized as a distinct entity characterized by unique pathologic features. Affected bile ducts show diffuse wall thickening, which represents transmural sclerosing inflammation composed of a dense lymphoplasmacytic infiltrate and fibrosis arranged at least focally in a storiform pattern. A diffuse IgG4-positive plasma cell infiltrate is demonstrable by immunohistochemistry. More than 90% of patients with IgG4-related sclerosing cholangitis have type 1 autoimmune pancreatitis, the remaining presenting as isolated cholangitis. The diagnosis requires a multidisciplinary approach, in which pathologic examination has a critical role. Tissue diagnosis on biopsy specimens (ie, bile duct biopsy, liver needle biopsies) is important, particularly for patients with isolated cholangitis, given the fact that radiological findings of IgG4-cholangitis are not reliable enough for establishing the diagnosis. Furthermore, serum IgG4 levels can be, albeit mildly, elevated in other biliary disorders. Histologic mimics of IgG4-related sclerosing cholangitis include primary sclerosing cholangitis, follicular cholangitis, and sclerosing cholangitis with granulocytic epithelial lesion, the latter 2 being recently described entities.

Autoimmune pancreatitis: an illustrated guide to diagnosis

Autoimmune pancreatitis (AIP) remains one of the rarer forms of pancreatitis but has become increasingly well recognized and widely diagnosed as it is an important differential, particularly due to the dramatic response to appropriate therapy. It is now best considered as part of a multisystem disease and the notion of "IgG4-related systemic sclerosing disease" has become widely recognized as the number of extra-pancreatic associations of AIP grows. More recently AIP has been classified into two subtypes: lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct-centric pancreatitis (IDCP) with distinct geographical, age and sex distributions for the two subtypes, in addition to different pathological characteristics. The role of imaging is crucial in AIP and should be considered in conjunction with clinical, serological, and histopathological findings to make the diagnosis. Radiologists are uniquely placed to raise the possibility of AIP and aid the exclusion of significant differentials to allow the initiation of appropriate management and avoidance of unnecessary intervention. Radiological investigation may reveal a number of characteristic imaging findings in AIP but appearances can vary considerably and the focal form of AIP may appear as a pancreatic mass, imitating pancreatic carcinoma. This review will illustrate typical and atypical appearances of AIP on all imaging modes. Emphasis will be placed on the imaging features that are likely to prove useful in discriminating AIP from other causes prior to histopathological confirmation. In addition, examples of relevant differential diagnoses are discussed and illustrated.

Clinical analysis of 36 cases of autoimmune pancreatitis in China

BACKGROUND

To improve the early identification of autoimmune pancreatitis in China by a retrospective analysis of clinical data from AIP patients.

METHODOLOGY/PRINCIPAL FINDINGS

The analysis included 36 patients admitted by the surgery department of our hospital from January 2003 to October 2011 whose postoperative pathological confirmations were consistent with the histological criteria of Honolulu Consensus Document. The clinical phenotypes associated with the histopathologic patterns of LPSP and IDCP were referred to as type 1 and type 2 of AIP, respectively. A retrospective analysis of clinical features, serological data, pathological findings and imageological records was performed in line with the subtypes of AIP. Type 1 showing a sex predilection (males) was commonly more dominant than type 2 in all AIP. Type 2 without a gender predilection was, on average, a decade younger than type 1. Type 1 was inferior to type 2 in ALT, ALP and γ-GT with statistical significance (P = 0.044, 0.025 and 0.013). Type 1 was inferior to type 2 in AST with difference close to statistical significance (P = 0.072). Histopathology revealed frequent lymphoplasmacytic infiltration with less frequent infiltration of neutrophils, eosinophils and fibroblasts. Diffuse and intensive interstitial fibrosis could be seen. The changes of pancreatic head were more frequently seen in type 2 than in type 1 (P = 0.05). Plasma cells staining of IgG4 at a density of over 30 or more cells per high-power field appeared to be a specific finding in China with type 1. Imageology found a diffusely or focally enlarged pancreas, most frequently a mass or enlargement in the pancreatic head, characteristic capsule-like rim, calcification or pancreatic calculus and cystic degeneration.

CONCLUSIONS/SIGNIFICANCE

AIP is a unique type of chronic pancreatitis and has distinctive serological, pathological and imageological characteristics, which should be used for differentiation from pancreatic cancer.

Autoimmune pancreatitis: assessment of the enhanced duct sign on multiphase contrast-enhanced computed tomography

PURPOSE

To assess the usefulness of the computed tomography (CT) finding of main pancreatic duct (MPD) wall enhancement, termed the "enhanced duct sign", for diagnosis of autoimmune pancreatitis (AIP) in comparison with diagnosis of pancreatic carcinoma and chronic pancreatitis.

MATERIALS AND METHODS

Two radiologists independently evaluated the presence or absence of the enhanced duct sign on multiphase contrast-enhanced CT in patients with AIP (n=55), pancreatic carcinoma (n=50), and chronic pancreatitis (n=50). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of AIP were calculated. In patients demonstrating the enhanced duct sign, additional findings were evaluated by consensus.

RESULTS

The enhanced duct sign was more frequently observed in patients with AIP (37/55, 67%) than in patients with pancreatic carcinoma (5/50, 10%) or chronic pancreatitis (0/50, 0%) (P<0.05). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of the finding were 0.67, 0.95, 0.85, 0.88, and 0.84, respectively. In AIP, the lumen within the enhanced duct was completely or partially invisible in 29 of 37 (78%) patients, and the enhanced duct was observed within the affected pancreatic parenchyma in 35 of 37 (95%) patients. In pancreatic carcinoma, the lumen within the enhanced duct was visible in all patients (5/5, 100%), and the enhanced duct was observed downstream of the tumor (5/5, 100%).

CONCLUSION

The enhanced duct sign is highly specific of AIP.

Differences between diffuse and focal autoimmune pancreatitis

AIM: To investigate differences in clinical features between diffuse- and focal-type autoimmune pancreatitis (AIP).

METHODS: Based on radiological findings by computed tomography and/or magnetic resonance imaging, we divided 67 AIP patients into diffuse type (D type) and focal type (F type). We further divided F type into head type (H type) and body and/or tail type (B/T type) according to the location of enlargement. Finally, we classified the 67 AIP patients into three groups: D type, H type and B/T type. We compared the three types of AIP in terms of clinical, laboratory, radiological, functional and histological findings and clinical course.

RESULTS: There were 34 patients with D-type, 19 with H-type and 14 with B/T-type AIP. Although obstructive jaundice was frequently detected in D-type patients (88%) and H-type patients (68%), no B/T-type patients showed jaundice as an initial symptom (P < 0.001). There were no differences in frequency of abdominal pain, but acute pancreatitis was associated more frequently in B/T-type patients (36%) than in D-type patients (3%) (P = 0.017). Serum immunoglobulin G (IgG)4 levels were significantly higher in D-type patients (median 309 mg/dL) than in B/T-type patients (133.5 mg/dL) (P = 0.042). Serum amylase levels in B/T-type patients (median: 114 IU/L) were significantly greater than in H-type patients (72 IU/L) (P = 0.049). Lymphoplasmacytic sclerosing pancreatitis (LPSP) was histologically confirmed in 6 D-type, 7 H-type and 4 B/T-type patients; idiopathic duct-centric pancreatitis was observed in no patients. Marked fibrosis and abundant infiltration of CD20-positive B lymphocytes with few IgG4-positive plasma cells were detected in 2 B/T-type patients. Steroid therapy was effective in all 50 patients (31 D type, 13 H type and 6 B/T type). Although AIP relapsed during tapering or after stopping steroids in 3 D-type and 3 H-type patients, no patients relapsed in B/T type. During follow-up, radiological features of 6 B/T-type patients were not changed and 1 B/T-type patient improved naturally.

CONCLUSION: Clinical features of H-type AIP were similar to those of D-type, but B/T-type differed from D and H types. B/T-type may involve diseases other than LPSP.

Diagnosis and management of autoimmune pancreatitis

• AIP is a heterogeneous disease with two distinct subtypes, now called type 1 and type 2. The proportions of these subtypes vary in their distribution worldwide. • Pancreatic cancer is the leading differential diagnosis for AIP, although AIP can mimic any other major pancreatobiliary disease. • Cross-sectional abdominal imaging CT/MRI should form the cornerstone to the diagnosis of AIP. • Serum IgG4 provides collateral evidence for the diagnosis of AIP and should not be the sole basis for the diagnosis. False-positive elevation in serum IgG4 can be seen in up to 10% of patients with pancreatic cancer. • A steroid trial should be performed only in select situations after ruling out pancreatic cancer and by gastroenterologists experienced in treating AIP. • Disease recurrence can be seen in up to 40% of patients after initial steroid therapy.

IgG4-related sclerosing disease: autoimmune pancreatitis and extrapancreatic manifestations

Autoimmune pancreatitis is the pancreatic manifestation of IgG4-related sclerosing disease, which recently was recognized as a distinct disease entity. Numerous extrapancreatic organs, such as the bile ducts, gallbladder, kidneys, retroperitoneum, thyroid, salivary glands, lung, mediastinum, lymph nodes, and prostate may be involved, either synchronously or metachronously. Most cases of autoimmune pancreatitis are associated with elevated serum IgG4 levels; extensive IgG4-positive plasma cells; and infiltration of lymphocytes into various organs, which leads to fibrosis. There are several established diagnostic criteria systems that are used to diagnose autoimmune pancreatitis and that rely on a combination of imaging findings of the pancreas and other organs, serologic findings, pancreatic histologic findings, and response to corticosteroid therapy. It is important to recognize multiorgan involvement of IgG4-related sclerosing disease and be familiar with its clinical and imaging features because it demonstrates a favorable response to treatment.

Characteristic magnetic resonance features of focal autoimmune pancreatitis useful for differentiation from pancreatic cancer

PURPOSE

To identify characteristic magnetic resonance (MR) features of focal autoimmune pancreatitis (f-AIP) useful for differentiation from pancreatic cancer (PC).

METHODS

We retrospectively analyzed MR imaging findings of 20 f-AIP lesions and 40 PC lesions smaller than 40 mm in diameter. On fat-suppressed T2-weighted images and dynamic contrast-enhanced fat-suppressed T1-weighted images (DCE-T1WI), we classified MR features of internal signal intensity for each lesion into homogeneous, speckled, or target type. We assessed the sensitivity, specificity, and accuracy of these findings in the diagnosis of f-AIP. We also investigated the incidence of previously reported findings for differentiation between f-AIP and PC.

RESULTS

Speckled enhancement within a hypointense or isointense lesion on pancreatic phase DCE-T1WI (speckled type) was observed more frequently in f-AIP than in PC, with high sensitivity, high specificity, and high accuracy. Hypointensity to hyperintensity surrounding a less enhanced focal area on DCE-T1WIs (target type) and upper stream main pancreatic duct dilatation were observed more frequently in PC than in f-AIP.

CONCLUSION

Speckled enhancement inside an f-AIP lesion on pancreatic phase DCE-T1WI was useful for differentiation from PC.

Type 1 autoimmune pancreatitis

Before the concept of autoimmune pancreatitis (AIP) was established, this form of pancreatitis had been recognized as lymphoplasmacytic sclerosing pancreatitis or non-alcoholic duct destructive chronic pancreatitis based on unique histological features. With the discovery in 2001 that serum IgG4 concentrations are specifically elevated in AIP patients, this emerging entity has been more widely accepted. Classical cases of AIP are now called type 1 as another distinct subtype (type 2 AIP) has been identified. Type 1 AIP, which accounts for 2% of chronic pancreatitis cases, predominantly affects adult males. Patients usually present with obstructive jaundice due to enlargement of the pancreatic head or thickening of the lower bile duct wall. Pancreatic cancer is the leading differential diagnosis for which serological, imaging, and histological examinations need to be considered. Serologically, an elevated level of IgG4 is the most sensitive and specific finding. Imaging features include irregular narrowing of the pancreatic duct, diffuse or focal enlargement of the pancreas, a peri-pancreatic capsule-like rim, and enhancement at the late phase of contrast-enhanced images. Biopsy or surgical specimens show diffuse lymphoplasmacytic infiltration containing many IgG4⁺ plasma cells, storiform fibrosis, and obliterative phlebitis. A dramatic response to steroid therapy is another characteristic, and serological or radiological effects are normally identified within the first 2 or 3 weeks. Type 1 AIP is estimated as a pancreatic manifestation of systemic IgG4-related disease based on the fact that synchronous or metachronous lesions can develop in multiple organs (e.g. bile duct, salivary/lacrimal glands, retroperitoneum, artery, lung, and kidney) and those lesions are histologically identical irrespective of the organ of origin. Several potential autoantigens have been identified so far. A Th2-dominant immune reaction and the activation of regulatory T-cells are assumed to be involved in the underlying immune reaction. IgG4 antibodies have two unique biological functions, Fab-arm exchange and a rheumatoid factor-like activity, both of which may play immune-defensive roles. However, the exact role of IgG4 in this disease still remains to be clarified. It seems important to recognize this unique entity given that the disease is treatable with steroids.

Utility of FDG PET/CT in IgG4-related systemic disease

IgG4-related systemic disease (IgG4-RSD) is an emerging clinical entity about which much remains to be elucidated, in terms of its aetiology, pathogenesis, diagnosis, treatment and outcome. Autoimmune pancreatitis (AIP) and Mikulicz disease (MD) are the two major, well-studied constituents of IgG4-RSD. AIP and MD have common characteristics of forming tumour-mimicking lesions that consist of lymphoplasmacytic infiltrates and fibrosclerosis with numerous immunoglobulin G4 (IgG4)-positive plasma cells, as well as various multi-organ manifestations of IgG4-RSD. 2-[(18)F]-fluoro-2-deoxy-d-glucose positron-emission tomography/ computed tomography (FDG PET/CT) enables the acquisition of whole-body images and provides functional information about disease activity; as such it has a valuable role in staging extent of disease, guiding biopsy, and monitoring response to treatment. However, FDG PET/CT is likely to be only one component of the management strategy, and clinical, laboratory, imaging and histological findings are crucial in the overall diagnosis of the condition. At present FDG PET/CT does not have a well-established role in the assessment of patients with IgG4-RSD and future prospective studies are required to define the cost-effectiveness and clinical impact in this patient group more accurately.

Mass-forming autoimmune pancreatitis and pancreatic carcinoma: differential diagnosis on the basis of computed tomography and magnetic resonance cholangiopancreatography, and diffusion-weighted imaging findings

PURPOSE

To differentiate mass-forming autoimmune pancreatitis (AIP) from pancreatic carcinoma by means of analysis of both computed tomography (CT) and magnetic resonance imaging (MRI) findings.

MATERIALS AND METHODS

Ten patients with mass-forming AIP diagnosed by revised clinical criteria of Japan Pancreas Society and 70 patients with pathologically proven pancreatic carcinoma were enrolled in this retrospective study. Two radiologists independently evaluated the CT and MR imaging findings. The sensitivity, specificity, and odds ratio of significant imaging findings and combinations of findings were calculated.

RESULTS

Seven findings were more frequently observed in AIP patients: (i) early homogeneous good enhancement, (ii) delayed homogeneous good enhancement, (iii) hypoattenuating capsule-like rim, (iv) absence of distal pancreatic atrophy, (v5) duct penetrating sign, (vi) main pancreatic duct (MPD) upstream dilatation ≤ 4 mm, and (vii) an apparent diffusion coefficient (ADC) ≤ 0.88 × 10(-3) mm(2) /s. When the findings of delayed homogeneous enhancement and ADC ≤ 0.88 × 10(-3) mm(2) /s were both used in diagnosis of mass-forming AIP, a sensitivity of 100% and a specificity of 100% were achieved. When 4 of any of the 7 findings were used in the diagnosis of AIP, a sensitivity of 100% and a specificity of 98% were achieved.

CONCLUSION

Analysis of a combination of CT and MR imaging findings allows for highly accurate differentiation between mass-forming AIP and pancreatic carcinoma.

Perfusion computed tomography findings of autoimmune pancreatitis

OBJECTIVES

The aim of this study was to clarify the pancreatic blood perfusion in patients with autoimmune pancreatitis (AIP) and the changes after steroid treatment.

METHODS

Perfusion computed tomography was performed in 11 patients with AIP and 12 control subjects. Pancreatic volumetric blood flow (F(V)), volume of distribution (V(D)), and blood transit time τ were determined from a single-compartment kinetic model. Nine patients with AIP were reexamined by perfusion computed tomography after corticosteroid administration.

RESULTS

The pancreatic F(V) values of the 11 patients with AIP (82.7/min) were significantly lower than those of control subjects (163.5/min, P = 0.0006). On the other hand, the pancreatic V(D) and τ values were not significantly different between AIP and normal. After steroid treatment, the F(V) values of 9 reexamined patients with AIP (76.2/min) were significantly elevated (109.8/min, P = 0.0391). However, the changes of the values after the treatment differed in degree among individuals. The values of 4 patients were dramatically elevated to greater than 100/min, whereas those of 4 other patients did not improve well. The value of the remaining patient whose initial F(V) value was normal (168.09/min) did not change after the treatment.

CONCLUSIONS

Pancreatic volumetric perfusion was attenuated in AIP patients. The perfusion was improved after the steroid treatment.

Autoimmune pancreatitis versus pancreatic cancer: a comprehensive review with emphasis on differential diagnosis

BACKGROUND

Autoimmune pancreatitis (AIP) is a rare form of chronic pancreatitis with a discrete pathophysiology, occasional diagnostic radiological findings, and characteristic histological features. Its etiology and pathogenesis are still under investigation, especially during the last decade. Another aspect of interest is the attempt to establish specific criteria for the differential diagnosis between autoimmune pancreatitis and pancreatic cancer, entities that are frequently indistinguishable.

DATA SOURCES

An extensive search of the PubMed database was performed with emphasis on articles about the differential diagnosis between autoimmune pancreatitis and pancreatic cancer up to the present.

RESULTS

The most interesting outcome of recent research is the theory that autoimmune pancreatitis and its various extra-pancreatic manifestations represent a systemic fibro-inflammatory process called IgG4-related systemic disease. The diagnostic criteria proposed by the Japanese Pancreatic Society, the more expanded HISORt criteria, the new definitions of histological types, and the new guidelines of the International Association of Pancreatology help to establish the diagnosis of the disease types.

CONCLUSION

The valuable help of the proposed criteria for the differential diagnosis between autoimmune pancreatitis and pancreatic cancer may lead to avoidance of pointless surgical treatments and increased patient morbidity.

Autoimmune pancreatitis mimicking pancreatic cancer

BACKGROUND/PURPOSE

Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis that can often be difficult to distinguish from pancreatic cancer. We describe the clinical and radiographic features of 23 patients with AIP whose presentations mimicked pancreatic cancer.

METHODS

A review of clinic, radiology, and endoscopy records from a 6-year period identified patients with AIP initially suspected of having pancreatic cancer. Abdominal computed tomography (CT) with intravenous contrast, endoscopic ultrasonography (EUS), and/or ERCP was performed in each patient. The diagnosis of AIP was made histologically and/or cytologically for each patient.

RESULTS

Nineteen of 23 patients (83%) presented with new-onset weight loss, jaundice, or both. Nineteen (83%) patients had CT findings worrisome for pancreatic cancer including: (1) pancreatic enlargement or focal mass, (2) regional lymphadenopathy, and/or (3) vascular invasion. Eighteen patients (78%) had common bile duct strictures on ERCP. EUS-guided fine-needle aspiration biopsies excluded pancreatic cancer in all 22 patients who had EUS (96%). Seven patients had surgery for continued suspicion of pancreatic cancer.

CONCLUSIONS

Although AIP commonly presents with features suggestive of pancreatic cancer, clinical recognition of AIP with appropriate diagnostic testing including EUS with fine-needle aspiration, ERCP, IgG4 levels, and pancreatic protocol CT expedites diagnosis and can spare patients unnecessary surgery.

Management strategies for autoimmune pancreatitis

INTRODUCTION

Autoimmune pancreatitis (AIP) is a newly developed concept for a peculiar type of pancreatitis, and at present is recognized as a pancreatic lesion reflecting IgG4-related systemic disease. It is of utmost importance to differentiate AIP from pancreatic cancer to avoid unnecessary surgery.

AREAS COVERED

The current management strategies for AIP, including its clinical features, diagnostic criteria, clinical subtypes, steroid therapy and prognosis are discussed, based on our 66 AIP cases and papers searched in PubMed from 1992 to March 2011, using the term 'autoimmune pancreatitis'. A new clinicopathological entity, an 'IgG4-related sclerosing disease' is also mentioned.

EXPERT OPINION

AIP should be considered in the differential diagnosis in elderly male patients presented with obstructive jaundice and pancreatic mass. Steroids are a standard therapy for AIP, but their regimen including maintenance therapy should be evaluated in prospective trials.

Morphologic patterns of autoimmune pancreatitis in CT and MRI

BACKGROUND/AIMS

To retrospectively evaluate the morphologic characteristics of autoimmune pancreatitis (AIP) using MRI and CT.

METHODS

86 dynamic contrast-enhanced CT and MRI scans in 36 AIP patients were evaluated regarding: different enlargement types, abnormalities of the main pancreatic duct (MPD), morphology of the parenchyma and other associated findings.

RESULTS

3 types of enlargement were found: (1) a focal type (28%), (2) a diffuse type (involving the entire pancreas, 11%) and (3) a combined type (56%). The MPD was usually dilated together with focal or diffuse narrowing in 67% (24/36). Unenhanced MRI showed AIP area in 56% (mostly T(1) hypo- and T(2) hyperattenuating), and CT in 10% (hypoattenuating). The arterial phase depicted similar patterns for CT and MRI (hypoattenuating in 58 and 52%, respectively). Venous and late venous phase patterns were usually hyperattenuating in MRI (65 and 74%, late enhancement), while CT mostly showed no signal differences (isoattenuating in 57 and 75%), yielding significant differences between CT and MRI for the venous (p < 0.0001) and the late phase (p = 0.025). Miscellaneous findings were: rim sign (25%), pseudocysts (8%) and infiltration of large vessels (11%).

CONCLUSIONS

The 'late-enhancement' sign seems to be a key feature and is best detectable with MRI. MRI may be recommended in the diagnostic workup of AIP patients. and IAP.

Renal involvement in patients with autoimmune pancreatitis: ultrasound findings

OBJECTIVE

The purpose of our study was to retrospectively evaluate the ultrasound findings of renal involvement in patients with autoimmune pancreatitis.

METHODS

15 patients with autoimmune pancreatitis (15 male, 0 female, mean age 66 years old, range 44-85) who had renal involvement documented on CT or MR and had abdominal ultrasound within 1 month were included. Ultrasound images were retrospectively reviewed for presence or absence of renal involvement. Shape and echogenicity of the renal lesions were recorded.

RESULTS

In 8 out of 15 patients, at least one renal lesion was identified on ultrasound with a total of 9 kidneys. In 7 kidneys, lesions appeared as ill-defined, non-mass like areas of decreased echogenicity. Three lesions showed associated irregular lobular thickening of the renal parenchyma with bulging contour and 1 showed focal area of parenchymal loss. In 2 kidneys, the lesions were seen as solitary or multiple hypoechoic mass-like areas. Ill-defined, non-mass like lesions on ultrasound corresponded to well-circumscribed wedge-shaped lesions in all but one case on CT or MR. Mass-like lesions on ultrasound corresponded to well-circumscribed round lesions on CT or MR.

CONCLUSION

Most common ultrasound findings of renal involvement in patients with autoimmune pancreatitis were ill-defined area of decreased echogenicity.

Magnetic resonance cholangiopancreatography for the diagnostic evaluation of autoimmune pancreatitis

OBJECTIVE

The aim of this study was to determine the role of magnetic resonance cholangiopancreatography (MRCP) for diagnosing autoimmune pancreatitis (AIP) and the accuracy of MRCP in depicting the main pancreatic duct (MPD) morphology of AIP using endoscopic retrograde cholangiopancreatography (ERCP) as the reference standard.

METHODS

Thirty-eight AIP patients, 40 pancreatic cancer patients, and 40 patients with normal pancreas were included. MRCP was interpreted in association with cross-sectional magnetic resonance images regarding MPD morphology, pancreatic parenchyma, and extrapancreatic abnormalities. Main pancreatic duct was interpreted as narrowed when a narrowed-appearing segment on MRCP was associated with upstream dilatation or pancreatic parenchymal abnormalities in the same location.

RESULTS

Accuracy of MRCP for depicting MPD morphology of AIP (64.7% [22/34]) was lower than those for pancreatic cancer (88.5% [23/26]) (P = 0.041) or normal pancreas (100% [40/40]) (P < 0.0005). The inaccuracy in AIP was primarily (10/12) due to overestimation of MPD narrowing. Of various differing MRCP findings between AIP and pancreatic cancer, multiple MPD narrowing (AIP vs cancer, 27/38 vs 0/40) and upstream MPD dilatation greater than 5 mm in diameter (AIP vs cancer, 0/38 vs 10/40) could exclude pancreatic cancer and AIP, respectively.

CONCLUSIONS

MRCP cannot replace ERCP for the diagnostic evaluation of AIP but may deserve to be used when ERCP has been unsuccessful or is difficult to perform.

Nonalcoholic, nonbiliary pancreatitis: cross-sectional imaging spectrum

OBJECTIVE

The purpose of this review is to describe the epidemiologic, etiopathogenetic, clinical, and imaging characteristics of various nonalcoholic, nonbiliary pancreatitis syndromes.

CONCLUSION

The spectrum of nonalcoholic, nonbiliary pancreatitis includes autoimmune pancreatitis, groove pancreatitis, hereditary pancreatitis, tropical pancreatitis, tuberculous pancreatitis, and metabolic pancreatitis. Advances in genetics and molecular pathology have shed new light on the etiopathogenesis and course of these syndromes. Accurate diagnosis aided by imaging findings allows optimal management.

Autoimmune pancreatitis with atypical imaging findings that mimicked an endocrine tumor

Autoimmune pancreatitis (AIP) is a rare cause of recurrent acute pancreatitis or chronic pancreatitis in middle-aged patients, and is characterised by a marked infiltration of lymphocytes and plasma cells in pancreatic tissue. Diagnosis of focal forms can be difficult as AIP may mimic pancreatic adenocarcinoma. Pediatric cases of AIP are exceptional. We report the case of a 15-year-old girl who had a focal AIP and associated cholangitis, with a very unusual vascularized mass that mimicked a pancreatic endocrine tumor. The diagnosis was obtained by a pancreatic biopsy, thus avoiding surgical resection, and all the clinical, biological and radiological abnormalities resolved after steroid therapy with 6 mo of follow-up.

Comparison of sclerosing cholangitis with autoimmune pancreatitis and infiltrative extrahepatic cholangiocarcinoma: multidetector-row computed tomography findings

PURPOSE

The aim of this study was to compare multidetector-row computed tomography (MDCT) findings between cases of sclerosing cholangitis with autoimmune pancreatitis (SC-AIP) and infiltrative extrahepatic cholangiocarcinoma (IEC).

MATERIALS AND METHODS

We retrospectively assessed MDCT findings from 16 IEC cases and 13 SC-AIP cases. MDCT findings were analyzed with regard to location, length, wall thickness, contour, stricture wall enhancement pattern, proximal duct diameter, and the presence of diffuse concentric thickening in the proximal duct and gallbladder wall thickness.

RESULTS

Stricture length, stricture wall thickness, and proximal duct diameter were significantly smaller for SC-AIP than for IEC: 19.3 +/- 8.7 vs. 31.8 +/- 12.0 mm (P = 0.004), 2.1 +/- 1.3 vs. 4.1 +/- 1.3 mm (P < 0.001), and 9.2 +/- 3.9 vs. 13.3 +/- 5.0 mm (P = 0.012), respectively. SC-AIP was correlated with stricture location in both the intrapancreatic and hilar hepatic bile ducts, concentric stricture contour (P < 0.001), and diffuse concentric thickening of the proximal bile duct (P = 0.010). Overall values of sensitivity, specificity, and accuracy used to distinguish between SC-AIP and IEC for stricture wall thickness of <3.0 mm and concentric contour were 76.9%, 93.8%, and 86.2%, respectively, and 100%, 87.5%, 93.1%, respectively.

CONCLUSION

Concentric contour and stricture wall thicknesses of <3.0 mm may help distinguish between SC-AIP and IEC.

Autoimmune pancreatitis

BACKGROUND

Autoimmune pancreatitis (AIP) is a relatively newly recognized type of pancreatitis that is characterized by diffuse or focal swelling of the pancreas due to lymphoplasmacytic infiltration and fibrosis of the pancreatic parenchyma.

MATERIAL AND METHODS

A PubMed literature search was performed using the keywords "autoimmune pancreatitis". Sometimes, bibliographies were cross-referenced and related article searches were performed once an article of interest was identified.

RESULTS

Pathologically, AIP shows narrowing of the pancreatic ducts and the intrapancreatic portion of the common bile duct. Obstructive jaundice is a common symptom at presentation, and pancreatic cancer represents an important clinical differential diagnosis. In late stages of the disease, the normal pancreatic parenchyma is often replaced by large amounts of fibrosis. Histologically, there seem to be two subtypes of the disease-one showing infiltration with IgG4-positive plasma cells but lacking granulocytic epithelial lesions (GELs), the other showing GELs but lacking strong IgG4 positivity. AIP is in at least some instances the pancreatic manifestation of a clinicopathological entity of IgG4-related systemic sclerosing disease. On the basis of pancreatic imaging, together with serological measurement of IgG4 and evaluation of other organ involvement, many AIP patients can be identified. The remaining patients require further diagnostic work-up. In these patients, pancreatic core needle biopsy and, as AIP responds to steroid treatment, also a trial with steroids, can help to differentiate AIP from pancreatic cancer. OUTLOOK AND DISCUSSION: This review presents the pathological, radiologic and laboratory findings of AIP. Moreover, the treatment and pathogenesis are discussed.