Utility of pancreatography for diagnosing autoimmune pancreatitis

Quantitative MR imaging biomarkers for distinguishing inflammatory pancreatic mass and pancreatic cancer-a systematic review and meta-analysis

OBJECTIVES

To evaluate the diagnostic performance of quantitative magnetic resonance (MR) imaging biomarkers in distinguishing between inflammatory pancreatic masses (IPM) and pancreatic cancer (PC).

METHODS

A literature search was conducted using PubMed, Embase, the Cochrane Library, and Web of Science through August 2023. Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) was used to evaluate the risk of bias and applicability of the studies. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were calculated using the DerSimonian-Laird method. Univariate meta-regression analysis was used to identify the potential factors of heterogeneity.

RESULTS

Twenty-four studies were included in this meta-analysis. The two main types of IPM, mass-forming pancreatitis (MFP) and autoimmune pancreatitis (AIP), differ in their apparent diffusion coefficient (ADC) values. Compared with PC, the ADC value was higher in MFP but lower in AIP. The pooled sensitivity/specificity of ADC were 0.80/0.85 for distinguishing MFP from PC and 0.82/0.84 for distinguishing AIP from PC. The pooled sensitivity/specificity for the maximal diameter of the upstream main pancreatic duct (dMPD) was 0.86/0.74, with a cutoff of dMPD ≤ 4 mm, and 0.97/0.52, with a cutoff of dMPD ≤ 5 mm. The pooled sensitivity/specificity for perfusion fraction (f) was 0.82/0.68, and 0.82/0.77 for mass stiffness values.

CONCLUSIONS

Quantitative MR imaging biomarkers are useful in distinguishing between IPM and PC. ADC values differ between MFP and AIP, and they should be separated for consideration in future studies.

CLINICAL RELEVANCE STATEMENT

Quantitative MR parameters could serve as non-invasive imaging biomarkers for differentiating malignant pancreatic neoplasms from inflammatory masses of the pancreas, and hence help to avoid unnecessary surgery.

KEY POINTS

• Several quantitative MR imaging biomarkers performed well in differential diagnosis between inflammatory pancreatic mass and pancreatic cancer. • The ADC value could discern pancreatic cancer from mass-forming pancreatitis or autoimmune pancreatitis, if the two inflammatory mass types are not combined. • The diameter of main pancreatic duct had the highest specificity for differentiating autoimmune pancreatitis from pancreatic cancer.

MRI features for differentiation of autoimmune pancreatitis from pancreatic ductal adenocarcinoma: A systematic review and meta-analysis

BACKGROUND AND AIMS

The accurate differential diagnosis between autoimmune pancreatitis (AIP) and pancreatic ductal adenocarcinoma (PDAC) is clinically important. We aimed to determine significant MRI features for differentiating AIP from PDAC, including assessment of diffusion-weighted imaging (DWI).

METHODS

We performed a systematic search using three databases. The pooled diagnostic odds ratio was calculated using a bivariate random effects model to determine significant MRI features for differentiating AIP from PDAC. The pooled sensitivity and specificity were calculated. The qualitative systematic review for DWI assessment was performed.

RESULTS

Of nine studies (775 patients), multiple main pancreatic duct (MPD) strictures, absence of upstream marked MPD dilatation, peripancreatic rim, and duct penetration sign were significant MRI features for differentiating AIP from PDAC. Absence of MPD dilatation had the highest pooled sensitivity (87%, 95% CI=68-96%), whereas peripancreatic rim had the highest pooled specificity (100%, 95% CI=88-100%). Of 12 studies evaluating DWI, seven reported statistically significant differences in apparent diffusion coefficient (ADC) values between AIP and PDAC; however, four reported lower ADC values in AIP than in PDAC, but three reported the opposite result.

CONCLUSION

The four significant MRI features can be useful to differentiate AIP from PDAC, but DWI assessment might be limited.

Autoimmune pancreatitis: What we know so far

Autoimmune pancreatitis (AIP) is a rare, often‐missed disease that involves inflammation of the pancreas and strictures of the pancreatic duct. Its prevalence and incidence in the United States remain scarce. The disease has a varied presentation and often mimics pancreatic malignancy, which can make the diagnosis challenging. Most patients have an excellent response to corticosteroid therapy. Immunomodulators may be used in some cases. Rituximab is an effective, emerging treatment in steroid‐refractory cases. This study aims to review the two distinct types of AIP and provide a detailed analysis of the diagnostic approach and treatment modalities.

Endoscopic retrograde cholangiopancreatography and intraductal ultrasonography in the diagnosis of autoimmune pancreatitis and IgG4-related sclerosing cholangitis

Endoscopic retrograde cholangiopancreatography is used to evaluate the narrowing of the main pancreatic duct in autoimmune pancreatitis (AIP) and biliary stricture in IgG4-related sclerosing cholangitis (IgG4-SC). Intraductal ultrasonography enables detailed visualization of the thickening of the bile duct wall in IgG4-SC. Pancreatic cancer, cholangiocarcinoma, and primary sclerosing cholangitis are important mimicking conditions of AIP and IgG4-SC. Diffuse or segmental stricture without marked upstream dilatation is a typical pancreatographic finding in AIP. By contrast, a single, short stricture with marked upstream dilatation is a typical finding in pancreatic cancer. The cholangiogram of IgG4-SC is classified into four types based on biliary stricture location, and this cholangiogram classification is useful for the differential diagnosis of IgG4-SC. Endoscopic retrograde cholangiography can be used to distinguish between IgG4-SC and primary sclerosing cholangitis. A segmental/long and intrapancreatic stricture is a characteristic finding of IgG4-SC, whereas band-like strictures, a beaded or pruned-tree appearance, and diverticulum-like outpouching are characteristic of primary sclerosing cholangitis. The characteristic intraductal ultrasonographic findings of circular-symmetrical wall thickening, smooth outer and inner margins, and homogeneous internal echo at the biliary stricture site are useful for diagnosis of IgG4-SC. Thickening of the bile duct wall at non-stricture sites is also a typical intraductal ultrasonographic finding of IgG4-SC and can be used for differential diagnosis from cholangiocarcinoma. Transpapillary bile duct and duodenal papilla biopsy during endoscopic retrograde cholangiopancreatography are also useful in the diagnosis of IgG4-SC.

Role of Endoscopic Ultrasonography and Endoscopic Retrograde Cholangiopancreatography in the Diagnosis of Pancreatic Cancer

Pancreatic cancer has the poorest prognosis among all cancers, and early diagnosis is essential for improving the prognosis. Along with radiologic modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), endoscopic modalities play an important role in the diagnosis of pancreatic cancer. This review evaluates the roles of two of those modalities, endoscopic ultrasonography (EUS) and endoscopic retrograde cholangiopancreatography (ERCP), in the diagnosis of pancreatic cancer. EUS can detect pancreatic cancer with higher sensitivity and has excellent sensitivity for the diagnosis of small pancreatic cancer that cannot be detected by other imaging modalities. EUS may be useful for the surveillance of pancreatic cancer in high-risk individuals. Contrast-enhanced EUS and EUS elastography are also useful for differentiating solid pancreatic tumors. In addition, EUS-guided fine needle aspiration shows excellent sensitivity and specificity, even for small pancreatic cancer, and is an essential examination method for the definitive pathological diagnosis and treatment decision strategy. On the other hand, ERCP is invasive and performed less frequently for the purpose of diagnosing pancreatic cancer. However, ERCP is essential in cases that require evaluation of pancreatic duct stricture that may be early pancreatic cancer or those that require differentiation from focal autoimmune pancreatitis.

The Diagnosis of Autoimmune Pancreatitis Using Endoscopic Ultrasonography

Autoimmune pancreatitis (AIP) is characterized by enlargement of the pancreas and irregular narrowing of the main pancreatic duct. It is often associated with IgG4-related sclerosing cholangitis (IgG4-SC), in which the bile duct narrows. Although characteristic irregular narrowing of the pancreatic duct caused by endoscopic retrograde cholangiopancreatography is noted in AIP, it is difficult to differentiate between localized AIP and pancreatic carcinoma based on imaging of the pancreatic duct. While stenosis of the bile duct in IgG4-SC is characterized by longer-length stenosis than in cholangiocarcinoma, differentiation based on bile duct imaging alone is challenging. Endoscopic ultrasound (EUS) can characterize hypoechoic enlargement of the pancreas or bile duct wall thickening in AIP and IgG4-SC, and diagnosis using elastography and contrast-enhanced EUS are being evaluated. The utility of EUS-guided fine needle aspiration for the histological diagnosis of AIP has been reported and is expected to improve diagnostic performance for AIP. Findings in the bile duct wall from endoscopic retrograde cholangiopancreatography followed by intraductal ultrasonography are useful in differentiating IgG4-SC from cholangiocarcinoma. Diagnoses based on endoscopic ultrasonography play a central role in the diagnosis of AIP.

The Challenge of Autoimmune Pancreatitis: A Portrayal From the Pediatric Perspective

Autoimmune pancreatitis (AIP) is a rare disorder characterized by prompt clinical response to corticosteroids. Lost tolerance to a variety of pancreatic antigens and subsequent development of autoantibodies are presumably involved in the initiation of AIP. Even pediatric patients have been reported with features of AIP, and awareness of this disorder is increasing among different clinicians. The terms lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-centric pancreatitis refer to the different histologic patterns of AIP, named type 1 and type 2, respectively. A combination of serologic, radiologic, and histologic investigations is needed to assess diagnosis of AIP and rule out neoplastic disorders. In addition, type 1 AIP can be distinguished by raised levels of serum immunoglobulin G4 and should be considered as part of systemic immunoglobulin G4-related disease. Conversely, type 2 AIP is frequently reported in younger patients and has less clear immune-mediated pathogenetic mechanisms. The natural history of pediatric AIP is obscure, and the diagnostic usefulness of different autoimmune abnormalities found in adults with AIP is limited for children. Tips to manage pediatric patients with AIP have been recently drafted through a set of recommendation statements. This review describes the current data about AIP and the pathogenic contribution of specific autoantibodies expressly in the pediatric population.

MR Imaging of Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) is characterized by autoimmune inflammatory destruction of the pancreatic tissue. Imaging plays an essential role in the diagnosis. AIP type 1 is the pancreatic manifestation of immunoglobulin G4 (IgG4)-related disease and is associated with IgG4-positive plasma cell infiltration and fibrosis of multiple organ systems. Type 2 is a related disease with pancreatic inflammation with or without concurrent inflammatory bowel disease. The authors demonstrate the imaging findings that are associated with the pancreatic and extra-pancreatic manifestations of AIP. They emphasize the common MR imaging and magnetic resonance cholangiopancreatography findings to help make the diagnosis of AIP.

Usefulness of three-dimensional magnetic resonance cholangiopancreatography with partial maximum intensity projection for diagnosing autoimmune pancreatitis

PURPOSE

To compare three-dimensional magnetic resonance cholangiopancreatography (MRCP) with/without partial maximum intensity projection (MIP) and endoscopic retrograde cholangiopancreatography (ERCP) in patients with autoimmune pancreatitis (AIP).

MATERIALS AND METHODS

Three-dimensional MRCP and ERCP images were retrospectively analyzed in 24 patients with AIP. We evaluated the narrowing length of the main pancreatic duct (NR-MPD), multiple skipped MPD narrowing (SK-MPD), and side branches arising from the narrowed portion of the MPD (SB-MPD) using four MRCP datasets: 5 original images (MIP₅), 10 original images (MIP₁₀), all original images (full-MIP), and a combination of these three datasets (a-MIP). The images were scored using a 3- or 5-point scale. The scores of the four MRCP datasets were statistically analyzed, and the positive rate of each finding was compared between MRCP and ERCP.

RESULTS

The median scores for SB-MPD on MIP₅ and a-MIP were significantly higher than those on MIP₁₀ and full-MIP. In other words, partial MIP is superior to full-MIP for visualization of detailed structures. The positive rate for SB-MPD on full-MIP was significantly lower than that on ERCP, whereas the positive rate on MIP₅, MIP₁₀, and a-MIP was not significantly different from that on ERCP. Moreover, the positive rate for NR-MPD and SK-MPD on the MRCP images was significantly higher than that on the ERCP images.

CONCLUSION

Partial MIP is useful for evaluating the MPD and is comparable with ERCP for diagnosing AIP.

Characteristic findings of endoscopic retrograde cholangiopancreatography in autoimmune pancreatitis

Background/Aims

Diffuse or segmental irregular narrowing of the main pancreatic duct (MPD), as observed by endoscopic retrograde cholangiopancreatography (ERCP), is a characteristic feature of autoimmune pancreatitis (AIP).

Methods

ERCP findings were retrospectively examined in 40 patients with AIP in whom irregular narrowing of the MPD was detected near the orifice. The MPD opening sign was defined as the MPD within 1.5 cm from the orifice being maintained. The distal common bile duct (CBD) sign was defined as the distal CBD within 1.5 cm from the orifice being maintained. Endoscopic findings of a swollen major papilla and histological findings of specimens obtained from the major papilla were examined in 26 and 21 patients, respectively.

Results

The MPD opening sign was detected in 26 of the 40 patients (65%). The distal CBD sign was detected in 25 of the 32 patients (78%), which showed stenosis of the lower bile duct. The patients who showed the MPD opening sign frequently showed the distal CBD sign (p=0.018). Lymphoplasmacytic infiltration, but not dense fibrosis, was histologically detected in biopsy specimens obtained from the major papilla.

Conclusions

On ERCP, the MPD and CBD adjacent to the major papilla are frequently maintained in patients with AIP involving the pancreatic head. These signs are useful for diagnosing AIP on ERCP.

Endoscopic retrograde pancreatography: When should we do it?

Endoscopic retrograde pancreatography (ERP) is an accurate imaging modality in the diagnosis of pancreatobiliary diseases. However, its use has been substantially reduced due to the invasiveness of procedure, the risk of complications and the widespread availability of non-invasive cross-section imaging techniques (computed tomography, magnetic resonance imaging, and endoscopic ultrasound). Since the introduction of endoscopic sphincterotomy, ERP has transformed from diagnostic method to an almost exclusively therapeutic procedure. Pancreatic duct injection substantially increased the risk of post-ERP pancreatitis (1.6%-15.7%); therefore, according to international guidelines ERP is recommended only in cases where biliary intervention is required. However, the role of ERP in the management of pancreatic diseases is currently not clearly defined, but in some cases the filling of pancreatic duct may provide essential information complementing the results of non-invasive imaging techniques. The aim of this publication is to systematically summarize the literature dealing with the diagnostic yield of ERP. We would like to define the precise indications of ERP and overview a diagnostic protocol of pancreatic diseases depending on international guidelines and the opinion of Hungarian experts, because it may improve the diagnostic accuracy, minimize of burden of patients and reduce the risk of procedure related complications.

Comparison of endoscopic retrograde cholangiopancreatography with papillary biopsy and endoscopic ultrasound-guided pancreatic biopsy in the diagnosis of autoimmune pancreatitis

BACKGROUND

International consensus diagnostic criteria (ICDC) have been proposed for the diagnostic criteria and algorithm of autoimmune pancreatitis (AIP). Although endoscopy is important in the diagnosis of AIP, practical patterns of its usage vary considerably worldwide. This study aimed to compare endoscopic retrograde cholangiopancreatography (ERCP) with papillary biopsy and endoscopic ultrasound (EUS)-guided pancreatic biopsy for diagnosing AIP using ICDC.

METHODS

We retrospectively reviewed and classified 165 Korean patients diagnosed by Korean criteria from June 2007 to October 2013. Among them, 61 patients underwent ERCP with duodenal papillary biopsy (group A) and 62 patients underwent EUS-guided pancreatic biopsy (group B). We analyzed the diagnostic criteria and levels of each criterion, and type of AIP before and after endoscopic procedures.

RESULTS

ERCP with papillary biopsy increased the diagnostic sensitivity from 65.6% (40/61) to 95.1% (58/61) (P < 0.01). EUS-guided pancreatic biopsy increased the diagnostic sensitivity from 50.0% (27/62) to 88.7% (55/62) (P < 0.01). The increases of diagnostic sensitivity in two endoscopic methods were not different statistically. In diagnosing definite AIP, EUS-guided pancreatic biopsy was more useful than ERCP with papilla biopsy (sensitivity; 79.0% vs. 65.6%, P < 0.01). EUS-guided pancreatic biopsy was helpful to classify type 1 and type 2 AIP in some patients. Procedure-related complication (mild pancreatitis) developed in one patient (1.6%) in group A and two patients (3.2%) in group B. ERCP with papillary biopsy was less expensive than EUS-guided pancreatic biopsy.

CONCLUSIONS

Both ERCP with papillary biopsy and EUS-guided pancreatic biopsy are safe and play important roles in diagnosing AIP according to the ICDC.

Endoscopic approaches for the diagnosis of autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is characterized by diffuse pancreatic enlargement and irregular narrowing of the main pancreatic duct (MPD). Immunoglobulin (Ig)G4-related sclerosing cholangitis (IgG4-SC) associated with AIP frequently appears as a bile duct stricture. Therefore, it is important to differentiate AIP and IgG4-SC from pancreatic cancer and cholangiocarcinoma or primary sclerosing cholangitis, respectively. Endoscopy plays a central role in the diagnosis of AIP and IgG4-SC because it provides imaging of the MPD and bile duct strictures as well as the ability to obtain tissue samples for histological evaluations. Diffuse irregular narrowing of MPD on endoscopic retrograde cholangiopancreatography (ERCP) is rather specific to AIP, but localized narrowing of the MPD is often difficult to differentiate from MPD stenosis caused by pancreatic cancer. A long stricture (>1/3 the length of the MPD) and lack of upstream dilatation from the stricture (<5 mm) might be key features of AIP on ERCP. Some cholangiographic features, such as segmental strictures, stric tures of the lower bile duct, and long strictures with prestenotic dilatation, are more common in IgG4-SC than in cholangiocarcinoma. Endoscopic ultrasonography (EUS) reveals diffuse hypoechoic pancreatic enlargement, sometimes with hypoechoic inclusions, in patients with AIP. In addition, EUS-elastography and contrast-enhanced harmonic EUS have been developed with promising results. The usefulness of EUS-guided fine-needle aspiration has been increasingly recognized for obtaining adequate tissue samples for the histological diagnosis of AIP. Further improvement of endoscopic procedures and devices will contribute to more accurate diagnosis of AIP and IgG4-SC.

Role of endoscopy in the diagnosis of autoimmune pancreatitis and immunoglobulin G4-related sclerosing cholangitis

Autoimmune pancreatitis (AIP) must be differentiated from pancreatic carcinoma, and immunoglobulin (Ig)G4-related sclerosing cholangitis (SC) from cholangiocarcinoma and primary sclerosing cholangitis (PSC). Pancreatographic findings such as a long narrowing of the main pancreatic duct, lack of upstream dilatation, skipped narrowed lesions, and side branches arising from the narrowed portion suggest AIP rather than pancreatic carcinoma. Cholangiographic findings for PSC, including band-like stricture, beaded or pruned-tree appearance, or diverticulum-like outpouching are rarely observed in IgG4-SC patients, whereas dilatation after a long stricture of the bile duct is common in IgG4-SC. Transpapillary biopsy for bile duct stricture is useful to rule out cholangiocarcinoma and to support the diagnosis of IgG4-SC with IgG4-immunostaining. IgG4-immunostaining of biopsy specimens from the major papilla advances a diagnosis of AIP. Contrast-enhanced endoscopic ultrasonography (EUS) and EUS elastography have the potential to predict the histological nature of the lesions. Intraductal ultrasonographic finding of wall thickening in the non-stenotic bile duct on cholangiography is useful for distinguishing IgG4-SC from cholangiocarcinoma. Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is widely used to exclude pancreatic carcinoma. To obtain adequate tissue samples for the histological diagnosis of AIP, EUS-Tru-cut biopsy or EUS-FNA using a 19-gauge needle is recommended, but EUS-FNA with a 22-gauge needle can also provide sufficient histological samples with careful sample processing after collection and rapid motion of the FNA needles within the pancreas. Validation of endoscopic imaging criteria and new techniques or devices to increase the diagnostic yield of endoscopic tissue sampling should be developed.

A case of obstructive jaundice due to autoimmune pancreatitis and a review of the literature

A 33-year-old man presented with jaundice, mild pancreatitis, and some weight loss. Laboratory tests showed cholestatic icterus. Imaging revealed distal bile duct obstruction and a mass in the head of the pancreas suspicious for cancer. Besides the enlargement of the head, the whole pancreatic parenchyma was altered. Therefore, autoimmune pancreatitis was considered. Endoscopic ultrasound biopsy found pancreatic tissue with lymphoplasmacytic inflammation and fibrosis. IgG4 serum concentration was within normal range. Due to the benign histology, a therapeutic attempt with prednisolone was initiated. The radiologic changes improved within 2 weeks, which supported the diagnosis of autoimmune pancreatitis. Bile duct obstruction and radiologic abnormalities of the pancreas completely resolved after a 4-month course of steroid treatment. Within 10 months, no relapse occurred. In context with this case, the recent literature was reviewed and the international consensus diagnostic criteria for autoimmune pancreatitis are summarized.

A proposal of a diagnostic algorithm with validation of International Consensus Diagnostic Criteria for autoimmune pancreatitis in a Japanese cohort

BACKGROUND

Among many diagnostic criteria for autoimmune pancreatitis (AIP), the International Consensus Diagnostic Criteria (ICDC) first enabled us to diagnose and compare type 1 and type 2 AIP, which permitted tailoring individual diagnostic algorithms depending on local expertise. We compared them and validated ICDC with special reference to levels 1 and 2, and proposed a diagnostic algorithm for AIP in Japan.

METHODS

The diagnostic sensitivity of 5 major criteria (ICDC, Korean, Japanese-2011, Asian, and HISORt criteria) was compared, using 61 patients with AIP. Fifty six patients with pancreatic cancer served as a control. Pancreas imaging on computed tomography (CT) and endoscopic retrograde pancreatography (ERP) were independently evaluated by 3 pancreatologists (5, 10, and 20 years of career experience) and each diagnostic criterion of ICDC was validated with special reference to levels 1 and 2.

RESULTS

The sensitivities of 5 major criteria were 95.1% (ICDC), 90.2% (Korean), 86.9% (Japanese), 83.6% (Asian), and 83.6% (HISORt) with 100% of specificity in each. In the evaluation of pancreas imaging, diagnostic sensitivities of combination with CT and ERP in segmental/focal type AIP were significantly higher than single imaging (26% in CT (P < 0.01) or 35% in ERP (P < 0.05) vs 63% in CT + ERP), but not significantly different in the diffuse type.

CONCLUSIONS

Of the 5 criteria, ICDC is the most sensitive and useful for diagnosing AIP. We have proposed a diagnostic algorithm with CT for the diffuse type of AIP, and combination with CT + ERP followed by EUS-FNA for the segmental/focal type.

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.

Treatment of autoimmune pancreatitis with the anecdotes of the first report

The first case that led researchers to put forward a new concept of autoimmune pancreatitis (AIP) was treated with steroids by gastroenterologists in Tokyo Women's Medical University. It is important to differentiate AIP from pancreatic cancer before treatment with steroids is started. Today, steroids are standard therapy for AIP worldwide. In the Japanese consensus guidelines, steroid therapy is indicated for symptomatic AIP. After management of glucose levels and obstructive jaundice, oral prednisolone is initiated at 0.6 mg/kg/day for 2-4 weeks and is gradually tapered to a maintenance dose of 2.5-5 mg/day over 2-3 months. To prevent relapse, maintenance therapy with low-dose prednisolone is used. For relapsed AIP, readministration or increased doses of steroids are effective. The presence of proximal bile duct stenosis and elevated serum IgG4 levels may be predictive of relapse of AIP. It is necessary to verify the validity of the Japanese regimen of steroid therapy for AIP. The necessity, drugs, and duration of maintenance therapy for AIP need to be clarified by prospective studies.

Strategy to differentiate autoimmune pancreatitis from pancreas cancer

Autoimmune pancreatitis (AIP) is a newly described entity of pancreatitis in which the pathogenesis appears to involve autoimmune mechanisms. Based on histological and immunohistochemical examinations of various organs of AIP patients, AIP appears to be a pancreatic lesion reflecting a systemic “IgG4-related sclerosing disease”. Clinically, AIP patients and patients with pancreatic cancer share many features, such as preponderance of elderly males, frequent initial symptom of painless jaundice, development of new-onset diabetes mellitus, and elevated levels of serum tumor markers. It is of uppermost importance not to misdiagnose AIP as pancreatic cancer. Since there is currently no diagnostic serological marker for AIP, and approach to the pancreas for histological examination is generally difficult, AIP is diagnosed using a combination of clinical, serological, morphological, and histopathological features. Findings suggesting AIP rather than pancreatic cancer include: fluctuating obstructive jaundice; elevated serum IgG4 levels; diffuse enlargement of the pancreas; delayed enhancement of the enlarged pancreas and presence of a capsule-like rim on dynamic computed tomography; low apparent diffusion coefficient values on diffusion-weighted magnetic resonance image; irregular narrowing of the main pancreatic duct on endoscopic retrograde cholangiopancreatography; less upstream dilatation of the main pancreatic duct on magnetic resonance cholangiopancreatography, presence of other organ involvement such as bilateral salivary gland swelling, retroperitoneal fibrosis and hilar or intrahepatic sclerosing cholangitis; negative work-up for malignancy including endoscopic ultrasound-guided fine needle aspiration; and steroid responsiveness. Since AIP responds dramatically to steroid therapy, accurate diagnosis of AIP can avoid unnecessary laparotomy or pancreatic resection.

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.