Autoimmune pancreatitis: imaging findings on contrast-enhanced MR, MRCP and dynamic secretin-enhanced MRCP

Imaging of pancreatic ductal adenocarcinoma - An update for all stages of patient management

Background

Pancreatic ductal adenocarcinoma (PDAC) is a common and lethal cancer. From diagnosis to disease staging, response to neoadjuvant therapy assessment and patient surveillance after resection, imaging plays a central role, guiding the multidisciplinary team in decision-planning.

Review aims and findings

This review discusses the most up-to-date imaging recommendations, typical and atypical findings, and issues related to each step of patient management. Example cases for each relevant condition are presented, and a structured report for disease staging is suggested.

Conclusion

Despite current issues in PDAC imaging at different stages of patient management, the radiologist is essential in the multidisciplinary team, as the conveyor of relevant imaging findings crucial for patient care.

Recent advances in IgG4-related autoimmune pancreatitis

The incidence of IgG4-related autoimmune pancreatitis (IgG4-AIP) is high in Asia and other countries, and unnecessary treatment is often undertaken due to both missed diagnosis and misdiagnosis in clinical practice. Although IgG4-AIP has attracted increasing attention, the details of IgG4-AIP pathogenesis and systemic immune response, including its relationship to tumor pathogenesis, are still unclear. In recent years, research on serum immunological detection, pathological features, clinical manifestations, diagnosis and treatment measures for IgG4-AIP has gradually increased. It is of great importance to summarize and discuss the latest progress regarding IgG4-AIP disease.

Late/delayed gadolinium enhancement in MRI after intravenous administration of extracellular gadolinium-based contrast agents: is it worth waiting?

The acquisition of images minutes or even hours after intravenous extracellular gadolinium-based contrast agents (GBCA) administration ("Late/Delayed Gadolinium Enhancement" imaging; in this review, further termed LGE) has gained significant prominence in recent years in magnetic resonance imaging. The major limitation of LGE is the long examination time; thus, it becomes necessary to understand when it is worth waiting time after the intravenous injection of GBCA and which additional information comes from LGE. LGE can potentially be applied to various anatomical sites, such as heart, arterial vessels, lung, brain, abdomen, breast, and the musculoskeletal system, with different pathophysiological mechanisms. One of the most popular clinical applications of LGE regards the assessment of myocardial tissue thanks to its ability to highlight areas of acute myocardial damage and fibrotic tissues. Other frequently applied clinical contexts involve the study of the urinary tract with magnetic resonance urography and identifying pathological abdominal processes characterized by high fibrous stroma, such as biliary tract tumors, autoimmune pancreatitis, or intestinal fibrosis in Crohn's disease. One of the current areas of heightened research interest revolves around the possibility of non-invasively studying the dynamics of neurofluids in the brain (the glymphatic system), the disruption of which could underlie many neurological disorders.

Complementary comments on diagnosis, severity and prognosis prediction of acute pancreatitis

The radiological differential diagnosis of acute pancreatitis includes diffuse pancreatic lymphoma, diffuse autoimmune pancreatitis and groove located mass lesions that may mimic groove pancreatitis. Dual energy computed tomography and diffusion weighted magnetic resonance imaging are useful in the early diagnosis of acute pancreatitis, and dual energy computed tomography is also useful in severity assessment and prognosis prediction. Walled off necrosis is an important complication in terms of prognosis, and it is important to know its radiological findings and distinguish it from pseudocyst.

Multimodality pictorial review of IgG4-related disease in the abdomen and pelvis

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a systemic, immune-mediated disease that can affect multiple organs, including the orbits, salivary glands, thyroid gland, lungs, aorta, pancreas, bile ducts, lymph nodes, and retroperitoneum. While timely diagnosis is particularly important given the efficacy of glucocorticoid treatment for IgG4-RD, accurate recognition can prove a challenge given the overlap between the imaging features of this disease and other entities.

PURPOSE

After a review of the epidemiology, pathophysiology, and clinical considerations (including treatment) associated with IgG4-RD, this pictorial review will showcase the variable imaging manifestations of this disease in the abdomen and pelvis. Post-treatment imaging appearance of these entities will be reviewed and mimickers of this disease in the abdomen and pelvis will be presented.

CONCLUSION

The presence of mass-like soft tissue with radiographic characteristics of fibrosis affecting multiple organs should raise suspicion for IgG4-RD, although definite diagnosis can only be made with appropriate clinical, serological, and pathologic data.

Pancreatic cancer, autoimmune or chronic pancreatitis, beyond tissue diagnosis: Collateral imaging and clinical characteristics may differentiate them

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies and is developing into the 2^nd leading cause of cancer-related death. Often, the clinical and radiological presentation of PDAC may be mirrored by other inflammatory pancreatic masses, such as autoimmune pancreatitis (AIP) and mass-forming chronic pancreatitis (MFCP), making its diagnosis challenging. Differentiating AIP and MFCP from PDAC is vital due to significant therapeutic and prognostic implications. Current diagnostic criteria and tools allow the precise differentiation of benign from malignant masses; however, the diagnostic accuracy is imperfect. Major pancreatic resections have been performed in AIP cases under initial suspicion of PDAC after a diagnostic approach failed to provide an accurate diagnosis. It is not unusual that after a thorough diagnostic evaluation, the clinician is confronted with a pancreatic mass with uncertain diagnosis. In those cases, a re-evaluation must be entertained, preferably by an experienced multispecialty team including radiologists, pathologists, gastroenterologists, and surgeons, looking for disease-specific clinical, imaging, and histological hallmarks or collateral evidence that could favor a specific diagnosis. Our aim is to describe current diagnostic limitations that hinder our ability to reach an accurate diagnosis among AIP, PDAC, and MFCP and to highlight those disease-specific clinical, radiological, serological, and histological characteristics that could support the presence of any of these three disorders when facing a pancreatic mass with uncertain diagnosis after an initial diagnostic approach has been unsuccessful.

Multimodel magnetic resonance imaging of mass-forming autoimmune pancreatitis: differential diagnosis with pancreatic ductal adenocarcinoma

PURPOSE

To assess the value of the multimodel magnetic resonance imaging (MRI), including unenhanced images, dynamic contrast-enhanced MRI (DCE-MRI), MR-cholangiopancreatography (MRCP), and diffusion-weighted imaging (DWI), in differentiation of mass-forming autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC).

METHODS

Twelve patients with mass-forming AIP and 30 with PDAC were included. All patients underwent unenhanced MRI, DCE-MRI, DWI, and MRCP. Relevant values including sensitivity and specificity of the imaging features and their diagnostic performance for predicting mass-forming AIP were analyzed.

RESULTS

Several statistically significant MR findings and quantitative indexes differentiating mass-forming AIP from PDAC, including multiplicity, irregularity or conformation, capsule-like rim enhancement, absence of internal cystic or necrotic portion, homogeneous enhancement during pancreatic, venous, and delayed phases, skipped stricture or stricture of MPD, absence of side branch dilation, maximum upstream MPD diameter < 2.4 mm, ContrastUP > 0.739, ContrastAP > 0.710, ContrastPP > 0.879, and ContrastVP or ContrastDP > 0.949, indicated mass-forming AIP (P < 0.05). The apparent diffusion coefficient (ADC) value was also significantly lower in mass-forming AIP compared to that in PDAC (P = 0.006). The cutoff value of ADC for distinguishing mass-forming AIP from PDAC was 1.099 × 10-3 mm2/s.

CONCLUSION

Multimodel MRI, including unenhanced MRI, DCE-MRI with DWI and MRCP can provide qualitative and quantitative information about mass-forming AIP characterization. Multimodel MRI are valuable for differentiating mass-forming AIP from PDAC.

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.

First Report of Sublingual Gland Ducts: Visualization by Dynamic MR Sialography and Its Clinical Application

This study was done to determine whether the sublingual gland ducts could be visualized and/or their function assessed by MR sialography and dynamic MR sialography and to elucidate the clinical significance of the visualization and/or evaluation of the function of sublingual gland ducts by clinical application of these techniques. In 20 adult volunteers, 19 elderly volunteers, and 7 patients with sublingual gland disease, morphological and functional evaluations were done by MR sialography and dynamic MR sialography. Next, four parameters, including the time-dependent changes (change ratio) in the maximum area of the detectable sublingual gland ducts in dynamic MR sialographic images and data were analyzed. Sublingual gland ducts could be accurately visualized in 16 adult volunteers, 12 elderly volunteers, and 5 patients. No significant differences in the four parameters in detectable duct areas of sublingual glands were found among the three groups. In one patient with a ranula, the lesion could be correctly diagnosed as a ranula by MR sialography because the mass was clearly derived from sublingual gland ducts. This is the first report of successful visualization of sublingual gland ducts. In addition, the present study suggests that MR sialography can be more useful in the diagnosis of patients with lesions of sublingual gland ducts.

Differentiation of focal autoimmune pancreatitis from pancreatic ductal adenocarcinoma

Autoimmune pancreatitis (AIP) is an inflammatory process of the pancreas that occurs most commonly in elderly males and clinically can mimic pancreatic adenocarcinoma and present with jaundice, weight loss, and abdominal pain. Mass-forming lesions in the pancreas are seen in the focal form of AIP and both clinical and imaging findings can overlap those of pancreatic cancer. The accurate distinction of AIP from pancreatic cancer is of utmost importance as it means avoiding unnecessary surgery in AIP cases or inaccurate steroid treatment in patients with pancreatic cancer. Imaging concomitantly with serological examinations (IgG4 and Ca 19-9) plays an important role in the distinction between these entities. Characteristic extra-pancreatic manifestations as well as favorable good response to treatment with steroids are characteristic of AIP. This paper will review current diagnostic parameters useful in differentiating between focal AIP and pancreatic adenocarcinoma.

Pancreas Solid Tumors

Solid tumors of the pancreas encompass a variety of diagnoses with treatments ranging from observation to major abdominal surgery. Pancreatic ductal adenocarcinoma remains one of the most common and most lethal of these differential of diagnoses and requires a multimodality approach through a multidisciplinary team of specialists. This article reviews the classification, clinical presentation, and workup in differentiating solid tumors of the pancreas and serves as an additional tool for general surgeons faced with such a clinical finding, from a surgical oncology perspective.

Imaging manifestations of immune-related adverse effects in checkpoint inhibitor therapies: A primer for the radiologist

Immune checkpoint inhibitors are monoclonal antibodies directed against cellular pathways on T-cells to treat different types of malignancies. This new therapy can cause immune-related adverse events that can involve almost any organ system. This article will review clinical presentations, molecular mechanisms and imaging manifestations of adverse events caused by checkpoint inhibitors and also illustrate the pseudoprogression tumor response pattern.

Pancreatic tumor in type 1 autoimmune pancreatitis: a diagnostic challenge

Background

The co-occurrence of type 1 autoimmune pancreatitis (AIP) and pancreatic tumor (PaT) has been previously reported. Pure AIP cases have favorable prognosis and are primarily treated with steroids, while AIP cases with PaT are associated with poor prognosis where the primary management is pancreatic resection. However, it’s a challenge to timely identify the concurrent PaT in AIP because of their similar clinical and radiological manifestations.

Methods

We retrospectively reviewed the data in two medical centers from January 2010 to April 2019. The inclusion criteria were as follows: 1) completion of abdominal CT imaging before invasive procedures to the pancreas, 2) a final diagnosis of type 1 AIP using the 2011 international consensus diagnostic criteria, 3) follow-up duration of at least one month unless AIP and PaT were identified simultaneously. The presence of PaT in AIP was made based on histopathological confirmation, and the absence of PaT in AIP was defined as no pathological or radiological evidence of concurrent PaT. Clinical and radiological characteristics including gender, age, surveillance period, serum IgG4 and Ca-199 levels, biopsy, extrapancreatic involvement, CT and MR (if performed) imaging characteristics were compared between AIP with and without PaT. The Fisher’s exact test was used for qualitative variables, and nonparametric Mann-Whitney test for quantitative variables. A p value ≤0.05 was considered statistically significant.

Results

A total of 74 patients with type 1 AIP were included, of which 5 (6.7%) had the concurrent PaT. The subtypes were pancreatic ductal adenocarcinoma (3/5), solitary extramedullary plasmacytoma in the pancreas (1/5) and cholangiocarcinoma in the pancreatic segment (1/5), respectively. Gender (p = 0.044), the pattern of pancreatic enlargement (p = 0.003), heterogeneity (p = 0.015), low-density (p = 0.004) on CT and rim enhancement on MRI (p = 0.050) differed significantly between AIP with and without PaT. None of the low-density characteristics on CT or other assessed MRI characteristics could significantly differentiate the two groups (p>0.05).

Conclusions

Female, focal pancreatic enlargement, pancreatic heterogeneity, low-density on CT and rim enhancement on MRI are suggestive of the concurrent PaT in type 1 AIP. The characteristics of low-density on CT or other MRI characteristics did not provide further diagnostic values.

Differentiating focal autoimmune pancreatitis and pancreatic ductal adenocarcinoma: contrast-enhanced MRI with special emphasis on the arterial phase

OBJECTIVES

To compare focal-type autoimmune pancreatitis (AIP) and pancreatic ductal adenocarcinoma (PDA) using contrast-enhanced MR imaging (CE-MRI), and to assess diagnostic performance of the lesion contrast at arterial phase (AP) (Contrast_AP) for differentiating between the two diseases.

METHODS

Thirty-six patients with focal-type AIP and 72 patients with PDA were included. All included patients underwent CE-MRI with triple phases. The signal intensity (SI) of the mass and normal pancreas was measured at each phase, and the lesion contrast (SI_pancreas/SI_mass) was compared between AIP and PDA groups. The sensitivity and specificity of Contrast_AP using an optimal cutoff point were compared with those of key imaging features specific to AIP and PDA.

RESULTS

The lesion contrast differed significantly between AIP and PDA groups at all phases of CE-MRI; the maximum difference was observed at AP. For AIP, the sensitivity (94.4%) and specificity (87.5%) of Contrast_AP (cutoff ≤ 1.41) were comparable or significantly higher than those of all key imaging features (sensitivity, 38.9-88.9%; specificity, 48.6-95.8%), except for the halo sign. For PDA, the sensitivity (87.5%) and specificity (94.4%) of Contrast_AP (cutoff > 1.41) were comparable or significantly higher than those of all key imaging features (sensitivity, 40.3-68.1%; specificity, 72.2-94.4%), except for the discrete mass.

CONCLUSIONS

Quantitative analysis of the lesion contrast using CE-MRI, particularly at AP, was helpful to differentiate focal-type AIP from PDA. The diagnostic performance of Contrast_AP was mostly comparable or higher than those of the key imaging features.

KEY POINTS

• Diagnosis of focal-type AIP vs. PDA using imaging techniques is extremely challenging. • Lesion contrast in the arterial-phase MRI differs significantly between focal-type AIP and PDA. • Quantitative analysis of lesion contrast using CE-MRI, particularly at the arterial phase, is helpful to differentiate focal-type AIP from PDA.

Type 1 and Type 2 Autoimmune Pancreatitis: Distinctive Clinical and Pathological Features, But Are There Any Differences at Magnetic Resonance? Experience From a Referral Center

OBJECTIVES

This study aimed to evaluate magnetic resonance imaging findings of autoimmune pancreatitis (AIP) and to find radiological patterns that could differentiate type 1 and type 2 AIP.

METHODS

Eighty-four patients with diagnosis of AIP were enrolled. Image analysis included pancreatic signal intensity abnormalities, enhancement pattern, extrapancreatic involvement, and main pancreatic duct alterations.

RESULTS

Pancreatic parenchyma resulted in hypointensity on T1-weighted images in 65 (98.5%) of 66 cases in type 1 and in 17 (94.5%) of 18 in type 2 (P > 0.05) and in hyperintensity on T2-weighted images in 41 (62%) of 66 and in 15 (83.4%) of 18, respectively (P > 0.05). Lesions were hypovascular in 64 (97%) of 66 cases in type 1 and in 16 (88.9%) of 18 in type 2 with delayed contrast retention in 56 (84.8%) of 66 and in 17 (94.5%) of 18, respectively (P > 0.05). Autoimmune cholangitis was found in 29 (43.9%) of 66 patients with type 1 and in 3 (16.7%) of 18 with type 2 (P = 0.02); renal involvement was observed in 20 (30.3%) of 66 and 1 (5.5%) of 18, respectively (P = 0.02). Both subtypes presented with multiple stenoses (P > 0.05). Dilation of upstream duct was more frequent in type 1 (P = 0.02).

CONCLUSIONS

Magnetic resonance imaging is useful in detecting extrapancreatic involvement, typically seen in type 1. Dilation of the upstream duct suggests type 1 AIP.

Comparison of diagnostic performance between CT and MRI in differentiating non-diffuse-type autoimmune pancreatitis from pancreatic ductal adenocarcinoma

OBJECTIVES

To intraindividually compare the diagnostic performance of CT and MRI in differentiating non-diffuse-type autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDA).

METHODS

Sixty-one patients with non-diffuse-type AIP and 122 patients with PDA, who underwent dynamic contrast-enhanced CT and MRI with MR pancreatography, were included. Two blinded radiologists independently rated their confidence in differentiating the two diseases on a 5-point scale, and the diagnostic performances of CT and MRI were compared. The presence of key imaging features to differentiate AIP and PDA were compared between CT and MRI.

RESULTS

The area under the receiver operating characteristic curve was significantly greater on MRI (0.993-0.995) than on CT (0.953-0.976) for both raters (p≤0.035). The sensitivities of MRI were higher than those of CT for the diagnosis of AIP (88.5-90.2% vs. 77-80.3%, p≤0.07) and PDA (97.5-99.2% vs. 91.8-94.3%, p≤0.031) for both raters, although the difference for AIP was statistically marginal (p=0.07) for rater 1. In AIP, multiple pancreatic masses, delayed homogeneous enhancement of the pancreatic mass, and multiple main pancreatic duct (MPD) strictures were observed significantly more frequently using MRI than CT (p≤0.008). In PDA, discrete pancreatic mass and MPD stricture were observed significantly more frequently using MRI than CT (p≤0.012).

CONCLUSIONS

The diagnostic performance of MRI is better for differentiating non-diffuse-type AIP from PDA, which is due to the superiority of MRI over CT in demonstrating the key distinguishing features of both diseases.

KEY POINTS

• Imaging differential diagnosis of non-diffuse-type AIP and PDA is challenging. • MRI has better diagnostic performance than CT in differentiating non-diffuse-type AIP from PDA. • MRI is superior to CT in demonstrating key distinguishing features of non-diffuse-type AIP and PDA.

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.

Abdominal manifestations of IgG4-related disease: a pictorial review

In the last decade, autoimmune pancreatitis has become recognised as part of a wider spectrum of IgG4-related disease, typically associated with elevated serum IgG4 levels and demonstrating a response to corticosteroid therapy. Radiologically, there is imaging overlap with other benign and neoplastic conditions. This pictorial review discusses the intra-abdominal manifestations of this disease on cross-sectional imaging before and after steroid treatment and the main radiological features which help to distinguish it from other key differentials.

TEACHING POINTS

• Autoimmune pancreatitis is part of a spectrum of IgG4-related disease. • Diagnosis is based on raised serum IgG4, clinical, radiological and histopathological findings. • Cross-sectional imaging can demonstrate the typical findings of abdominal IgG4-related disease. • Cross-sectional imaging can be used to monitor response to corticosteroid treatment.

A Rare Multifocal Pattern of Type 2 Autoimmune Pancreatitis with Negative IgG4: A Potential Diagnostic Pitfall That May Mimic Multifocal Pancreatic Adenocarcinoma

Autoimmune pancreatitis (AIP) is an increasingly recognized form of acute pancreatitis characterized by obstructive jaundice with a rapid and dramatic treatment response to steroid therapy. Recently, AIP has been divided into two distinct phenotypes: lymphoplasmocytic sclerosing pancreatitis AIP (type 1) and idiopathic duct-centric pancreatitis AIP (type 2); each of which have their own distinct demographics, diagnostic criteria, and histopathological features. We report, to the best of our knowledge, the first case of a multifocal pattern of type 2 AIP characterized with both CT and MR imaging. This rare imaging pattern of AIP may mimic the appearance of more worrisome malignant etiologies such as multifocal pancreatic adenocarcinoma or lymphoma, with overlapping imaging characteristics potentially complicating or delaying diagnosis. Therefore, recognition of this atypical pattern of AIP and avoidance of this potential diagnostic pitfall is crucial.

The clinical value of secretin-enhanced MRCP in the functional and morphological assessment of pancreatic diseases

Secretin-enhanced magnetic resonance cholangiopancreatography (S-MRCP) provides a non-invasive way, with which, to evaluate pancreatic duct (PD) anatomy and exocrine pancreatic function. S-MRCP can be added to the routine pancreas MR examination in equivocal cases. Moreover, it can detect subtle PD involvement, allowing diagnosis of early, rather than end-stage, pancreatic diseases. Although S-MRCP is a valuable non-invasive diagnostic method, it is only performed in a few centres due to relative high cost. Furthermore, less familiarity with its indications, the examination technique, and image interpretation also contribute to its limited use. Thus, the purpose of this article is to explain secretin's mechanism of action, the examination technique, the clinically relevant indications, the advantages, and limitations. Finally, we will focus on image analysis and its role in achieving an early and accurate diagnosis of specific pancreatic and PD diseases.

Imaging Features of Toxicities by Immune Checkpoint Inhibitors in Cancer Therapy

Purpose of review

With the increasing use of immune checkpoint inhibitors in cancer therapy radiographic profiling of frequent and serious immune-related adverse events (irAEs) becomes more relevant. This article reviews imaging features of irAEs induced by the anti-CTLA-4 and anti-PD-1 antibodies ipilimumab, nivolumab and pembrolizumab.

Recent findings

Important radiological manifestations are immune-related colitis, hepatitis, pancreatitis, hypophysitis, pneumonitis, arthritis and sarcoid-like lymphadenopathy. Typical imaging features are summarized and compared with other relevant differential diagnoses.

Summary

Early diagnosis and appropriate therapeutic decisions are required for a successful treatment of irAEs. In addition to staging and follow-up imaging, identification and monitoring of adverse events becomes an important radiologic aspect in oncologic care.

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.

From Pathogenesis, Clinical Manifestation, and Diagnosis to Treatment: An Overview on Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) is a special type of chronic pancreatitis which is autoimmune mediated. The international consensus diagnostic criteria (ICDC) 2011 proposed two types of AIP: type I is associated with histological pattern of lymphoplasmacytic sclerosing pancreatitis (LPSP), characterized by serum IgG4 elevation, whereas type 2 is named idiopathic duct-centric pancreatitis (IDCP), with granulocytic epithelial lesion (GEL) and immunoglobulin G4 (IgG4) negative. The pathogenic mechanism is unclear now; based on genetic factors, disease specific or related antigens, innate and adaptive immunity may be involved. The most common clinical manifestations of AIP are obstructive jaundice and upper abdominal pain. The diagnosis can be made by a combination of parenchymal and ductal imaging, serum IgG4 concentrations, pancreatic histology, extrapancreatic disease, and glucocorticoid responsiveness according to ICDC 2011. Because of the clinical and imaging similarities with pancreatic cancer, general work-up should be done carefully to exclude pancreatic malignant tumor before empirical trial of glucocorticoid treatment. Glucocorticoid is the most common drug for AIP to induce remission, while there still exists controversy on steroid maintenance and treatment for relapse. Further studies should be done to identify more specific serum biomarkers for AIP, the pathogenic mechanisms, and the treatment for relapse.

Pancreatic duct stenosis: Differential diagnosis between malignant and benign conditions at secretin-enhanced MRCP

PURPOSE

To define imaging criteria of benign and malignant nature in patients with main pancreatic duct (MPD) stenosis.

MATERIALS-METHODS

S-MRCPs of 35 patients with pancreatitis and 14 with adenocarcinoma were evaluated.

RESULTS

Adenocarcinoma caused higher prevalence of complete stenosis (14/14-100% vs 17/35-49%), dilated side-branches (14/14-100% vs 18/35-51%) and lower prevalence of duct-penetrating sign (0/14-0% vs 31/35-89%). The number of stenoses was higher in benign conditions (mean 1.4 Vs 1). Upstream MPD diameter was higher in cancer-induced stenoses (4.5 vs 2.9mm).

CONCLUSIONS

Single complete stenosis with dilated side branches, increased MPD caliber and absent duct-penetrating sign are suggestive of malignancy.

Secretin-stimulated MR cholangiopancreatography: spectrum of findings in pancreatic diseases

Abstract

MR cholangiopancreatography (MRCP) is an imaging technique that has evolved over the past 2 decades and that continues to have a fundamental role in the non-invasive detection of morphologic features of the pancreatic ducts. In several studies, MRCP has shown a good correlation with endoscopic retrograde cholangiopancreatography in the evaluation of diseases and anatomic variants of the pancreatic ductal system. However, in physiologic conditions the pancreatic ducts are not always easily recognisable. More recently, secretin-enhanced MRCP protocols have been developed for a more complete assessment of pancreatic ducts and glandular function, including monitoring of pancreatic flow dynamics and duodenal filling after pancreatic hormonal stimulation with secretin. The injection of this hormone causes temporary dilation of the pancreatic ducts, principally by increasing pancreatic exocrine secretions, and thus improving MRCP detection of the ducts and characterisation of pancreatic disorders and allowing the assessment of the exocrine pancreatic reserve. The purpose of this pictorial review is to summarise the technical aspects of secretin-stimulated MRCP, to report the secretin-stimulated MRCP findings of pancreatic duct abnormalities and to review the diagnostic capabilities of secretin-stimulated MRCP in various pancreatic ductal system conditions.

Main Messages

• MRCP has a fundamental role in the non-invasive detection of pancreatic ducts.

• In physiologic conditions pancreatic ducts are not always well detected on MRCP.

• Secretin injection causes temporary dilation of pancreatic ducts and thus improves MRCP detection.

• Secretin-stimulated MRCP may allow the assessment of the exocrine pancreatic reserve.

• Secretin increases the diagnostic capabilities of MRCP for evaluating pancreatic disorders.

Secretin-Stimulated Magnetic Resonance Imaging Assessment of the Benign Pancreatic Disorders: Systematic Review and Proposal for a Standardized Protocol

This systemic review summarizes the current literature and general consensus on secretin-stimulated magnetic resonance imaging (s-MRI) of the benign pancreatic disorders and discusses important aspects on how s-MRI is optimally performed. The aim is to provide an overview, for clinicians and radiologist, of the s-MRI protocols and the range of clinical applications. Furthermore, the review will summarize the criteria for evaluation of pancreatic morphology and function based on s-MRI.The literature search indentified 69 original articles and 15 reviews. Chronic pancreatitis was the disease that was most frequently assessed by s-MRI (33%), followed by acute pancreatitis (9%). Dynamic thick-slab 2-dimensional magnetic resonance cholangiopancreatography was the most used imaging sequence (86%). The diameter of the main pancreatic duct (75%) and pancreatic exocrine function based on visual grading of duodenal filling (67%) were the most evaluated pancreatic features. Sufficient similarities between studies were identified to propose the most agreeable standardized s-MRI protocol for morphological and functional assessment of the pancreas. In the future, more research and increased collaboration between centers is necessary to achieve more consensus and optimization of s-MRI protocols.

Imaging features of immunoglobulin G4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition that was first recognised as a systemic disease in 2003, when patients with autoimmune pancreatitis were found to have extrapancreatic manifestations. Since 2003, IgG4-RD has been described in a diverse range of other organs including the biliary tree, orbits, lacrimal glands, salivary glands, lungs, kidneys, aorta, retroperitoneum, lymph nodes, pachymeninges, prostate and pituitary gland. The disease frequently occurs in the absence of pancreatic involvement. The imaging manifestations of IgG4-RD are broad and variable depending on the organ involved. The majority of individual organ appearances are non-specific and differentiation between IgG4-RD and potentially more serious conditions is not usually possible based on radiological findings in one organ alone. However, if there are simultaneous findings typical of IgG4-RD in multiple organs then this is a key diagnostic clue and IgG4-RD should be considered as one of the main differentials. This review article examines the spectrum of imaging appearances of IgG4-RD. Increased awareness of the spectrum of radiological appearances of IgG4-RD throughout the body and subsequent consideration of the condition may potentially avoid invasive treatment and lead to more prompt corticosteroid therapy.

Differentiation of mass-forming focal pancreatitis from pancreatic ductal adenocarcinoma: value of characterizing dynamic enhancement patterns on contrast-enhanced MR images by adding signal intensity color mapping

OBJECTIVES

To evaluate the value of dynamic enhancement patterns on contrast-enhanced MR images by adding signal intensity colour mapping (SICM) to differentiate mass-forming focal pancreatitis (MFFP) from pancreatic ductal adenocarcinoma (PDAC).

METHODS

Forty-one clinicopathologically proven MFFPs and 144 surgically confirmed PDACs were enrolled. Laboratory and MR imaging parameters were used to differentiate MFFP from PDAC. In particular, enhancement patterns on MR images adding SICM were evaluated. By using classification tree analysis (CTA), we determined the predictors for the differentiation of MFFP from PDAC.

RESULTS

In the CTA, with all parameters except enhancement pattern on SICM images, ductal obstruction grade and T1 hypointensity grade of the pancreatic lesion were the first and second splitting predictor for differentiation of MFFP from PDAC, in order. By adding an enhancement pattern on the SICM images to CTA, the enhancement pattern was the only splitting predictor to differentiate MFFP from PDAC. The CTA model including enhancement pattern on SICM images has sensitivity of 78.0 %, specificity of 99.3 %, and accuracy of 94.6 % for differentiating MFFP from PDAC.

CONCLUSION

The characterization of enhancement pattern for pancreatic lesions on contrast-enhanced MR images adding SICM would be helpful to differentiate MFFP from PDAC.

KEY POINTS

• SICM was useful to characterize enhancement pattern. • Enhancement pattern on SICM was the only splitting predictor on CTA. • This model may be useful for differentiating MFFP from PDAC.

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.

Autoimmune pancreatitis: Multimodality non-invasive imaging diagnosis

Autoimmune pancreatitis (AIP) is characterized by obstructive jaundice, a dramatic clinical response to steroids and pathologically by a lymphoplasmacytic infiltrate, with or without a pancreatic mass. Type 1 AIP is the pancreatic manifestation of an IgG4-related systemic disease and is characterized by elevated IgG4 serum levels, infiltration of IgG4-positive plasma cells and extrapancreatic lesions. Type 2 AIP usually has none or very few IgG4-positive plasma cells, no serum IgG4 elevation and appears to be a pancreas-specific disorder without extrapancreatic involvement. AIP is diagnosed in approximately 2%-6% of patients that undergo pancreatic resection for suspected pancreatic cancer. There are three patterns of autoimmune pancreatitis: diffuse disease is the most common type, with a diffuse, “sausage-like” pancreatic enlargement with sharp margins and loss of the lobular contours; focal disease is less common and manifests as a focal mass, often within the pancreatic head, mimicking a pancreatic malignancy. Multifocal involvement can also occur. In this paper we describe the features of AIP at ultrasonography, computed tomography, magnetic resonance and positron emission tomography/computed tomography imaging, focusing on diagnosis and differential diagnosis with pancreatic ductal adenocarcinoma. It is of utmost importance to make an early correct differential diagnosis between these two diseases in order to identify the optimal therapeutic strategy and to avoid unnecessary laparotomy or pancreatic resection in AIP patients. Non-invasive imaging plays also an important role in therapy monitoring, in follow-up and in early identification of disease recurrence.

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.

Differentiating autoimmune pancreatitis from pancreatic adenocarcinoma using dual-phase computed tomography

OBJECTIVE

This article aimed to study features on dual-phase computed tomography (CT) that help differentiate autoimmune pancreatitis (AIP) from pancreatic adenocarcinoma (PA).

METHODS

The CTs of 32 patients with AIP were matched with equal number of PA and were independently evaluated by 3 radiologists who assigned a diagnosis of AIP, PA, or unsure. Interobserver agreement between radiologists was evaluated using κ statistics.

RESULTS

The mean accuracies for diagnosing AIP and PA were 68% and 83%, respectively. There was moderate agreement between radiologists (κ, 0.58; P < 0.0001). The most common findings for AIP were common bile duct (CBD) stricture (63%), bile duct wall hyperenhancement (47%), and diffuse parenchymal enlargement (41%). The most common findings for PA were focal mass (78%; κ, 0.58; P < 0.0001) and pancreatic ductal dilatation (69%; κ, 0.7; P < 0.0001). Findings helpful for diagnosing AIP were diffuse enlargement, parenchymal atrophy as well as absence of pancreatic duct dilatation and focal mass. Findings helpful for diagnosing PA were focal mass and pancreatic ductal dilatation. Misdiagnosis of PA in patients with AIP was due to focal mass, pancreatic duct dilatation, and pancreatic atrophy, whereas misdiagnosis of AIP in patients with PA was due to absence of atrophy, presence of diffuse enlargement, and peripancreatic halo.

CONCLUSIONS

Diffuse enlargement, hypoenhancement, and characteristic peripancreatic halo are strong indicators for a diagnosis of AIP. Radiologists demonstrated moderate agreement in distinguishing AIP from PA on the basis of CT imaging.

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.

Autoimmune pancreatitis: role of endoscopy in diagnosis and treatment

This review addresses the role of endoscopy in the diagnosis and treatment of autoimmune pancreatitis (AIP) and provides a diagnostic process for patients with suspected AIP. When should AIP be suspected? When can it be diagnosed without endoscopic examination? Which endoscopic approaches are appropriate in suspected AIP, and when? What are the roles of diagnostic endoscopic retrograde pancreatography, endoscopic biopsies, and IgG4 immunostaining? What is the proper use of the steroid trial in the diagnosis of AIP in patients with indeterminate computed tomography imaging? Should biliary stenting be performed in patients with AIP with obstructive jaundice?

Distinguishing autoimmune pancreatitis from pancreaticobiliary cancers: current strategy

OBJECTIVE

A review of the literature to identify current modalities for the diagnosis of autoimmune pancreatitis (AIP) with the objective of establishing a strategy to distinguish it from pancreaticobiliary cancers.

BACKGROUND

Pancreatic and biliary manifestations of AIP mimic pancreaticobiliary cancers. Misdiagnosis of AIP can result in major surgery for a steroid-responsive disease.

METHODS

A review of the literature was performed to identify recent advances in the diagnosis of AIP and evaluate outcomes with various diagnostic strategies to minimize operative intervention for an autoimmune disease.

RESULTS

Diagnostic criteria for AIP are based on histology, imaging, serology, extrapancreatic organ involvement, and response to steroid therapy. The most commonly involved extrapancreatic sites are bile duct, kidney, and retroperitoneum. The Mayo Clinic diagnostic strategy utilizes core biopsy of the pancreas and the Japanese strategy depends on a characteristic pancreatogram. The rate of operative intervention was similar with both strategies and none of the patients with cancer received steroid therapy. Immunoglobulin G subtype 4 (IgG4)-associated cholangitis mimics cholangiocarcinoma and presence of more than 10 IgG4-positive plasma cells/high power field on endoscopic biopsy of the bile duct was diagnostic for AIP in 88% patients. Biliary complications and early relapse are common after surgical resection and immunomodulatory drugs can maintain long-term remission.

CONCLUSION

Criteria based on histology, imaging, endoscopy, serology, extrapancreatic organ involvement, and response to steroid therapy improve the diagnostic yield for AIP. Application of diagnostic and therapeutic protocols by a multidisciplinary team will optimize outcomes with a decline in the rate of operative intervention for AIP, a steroid-responsive disease with propensity for relapse.

Magnetic resonance imaging findings of the mass-forming type of autoimmune pancreatitis: comparison with pancreatic adenocarcinoma

PURPOSE

To determine the characteristic magnetic resonance imaging (MRI) features of mass-forming autoimmune pancreatitis (AIP), which allow its differentiation from pancreatic adenocarcinoma (PAC).

MATERIALS AND METHODS

MR images of 37 patients with either pathologically proven, mass-forming AIPs (n = 9) or PACs (n = 28) were retrospectively reviewed. The pancreatic MR protocol included unenhanced images, contrast-enhanced dynamic images, diffusion-weighted imaging (DWI), and MR-cholangiopancreatography (MRCP). Two reviewers analyzed the MR images regarding the number, location, morphologic features, and enhancement degree and pattern of the lesions as well as secondary changes of the pancreatic parenchyma, the biliary and pancreatic ducts. The size and apparent diffusion coefficient (ADC) values of the lesions were measured.

RESULTS

Although sensitivities were low (28.6%-44.4%), specificities of multiplicity, capsule-like rim enhancement, and skipped stricture of the biliary or pancreatic duct in mass-forming AIP were high (100%). Sensitivities and specificities of irregular or geographic shape, delayed enhancement, and a low ADC value <1.26 × 10(-3) mm(2) /s in mass-forming AIP were favorable (71.4%-83.3% and 78.5%-89.3%).

CONCLUSION

Although to differentiate mass-forming AIP from pancreatic cancer is difficult, the combination of MRI findings including contrast-enhanced dynamic images, MRCP, and DWI can be a help.

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.

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.

[Clinical characteristics of autoimmune pancreatitis]

Korean autoimmune pancreatitis (AIP) criteria 2007 was aimed to diagnose the wide spectrum of AIP with high sensitivity. The most crucial issue when caring for patients with suspected AIP is to differentiate AIP from pancreatic cancer. Pancreatic cancer can be distinguished from AIP by pancreatic imaging, measurement of serum IgG4 levels, endoscopic ultrasound guided fine needle aspiration and trucut biopsy, and steroid trial. Autoimmune pancreatitis is a rare systemic fibroinflammatory disease which can affect not only the pancreas, but also a variety of organs such as the bile ducts, salivary glands, retroperitoneum, and lymph nodes. Organs affected by AIP have a lymphoplasmacytic infiltrate rich in IgG4-positive cells. This inflammatory process responds dramatically to oral steroid therapy. Granulocytic epithelial lesion (GEL) positive AIP patients differ from GEL negative AIP patients in clinical features such as equal gender ratio, younger mean age, no increase in serum IgG4, no association with extrapancreatic involvement, no relapse, and frequent association with inflammatory bowel disease. Further investigation is needed to clarify the pathogenic mechanisms including more definite serological markers for theses two entities.

Autoimmune pancreatitis: pancreatic and extrapancreatic MR imaging-MR cholangiopancreatography findings at diagnosis, after steroid therapy, and at recurrence

PURPOSE

To determine and describe the magnetic resonance (MR) imaging-MR cholangiopancreatographic pancreatic and extrapancreatic findings of autoimmune pancreatitis (AIP) and the probability, site, and MR features of recurrent AIP after steroid therapy.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board, and the requirement for informed patient consent was waived. The data of 27 patients with AIP were included in the study. All patients had undergone MR imaging with MR cholangiopancreatography before and after steroid treatment and during follow-up (median follow-up period, 45 months). Image analysis included assessment of pancreatic parenchyma enlargement, signal intensity on T1- and T2-weighted MR images, contrast enhancement, and presence of bile duct and/or renal involvement. The probability of AIP recurrence was assessed by using Kaplan-Meier curves and the unadjusted Cox model.

RESULTS

At the time of diagnosis, the AIP-affected pancreatic parenchyma showed diffuse enlargement in 14 (52%) of the 27 patients and segmental enlargement in 13 (48%). The pancreatic parenchyma appeared hypointense on T1-weighted images in all 27 (100%) patients, hyperintense on T2-weighted images in 25 (93%), and isointense in two (7%). During the pancreatic phase of the dynamic contrast material-enhanced study, the affected pancreatic parenchyma appeared hypointense in 25 (93%) patients and isointense in two (7%). During the portal venous and delayed phases, the images of 19 (70%) patients showed delayed enhancement. Bile duct involvement was observed in 10 (37%) patients, and renal involvement was observed in two (7%). After steroid treatment, six (22%) patients had recurrent AIP, with a median disease-free interval of 20.6 months. The sites of recurrence were the pancreas and the kidneys in three of the six patients, solely the pancreas in two patients, and the biliary ducts in one patient.

CONCLUSION

MR imaging with MR cholangiopancreatography enables the diagnosis of pancreatic and extrapancreatic AIP and the assessment of changes after steroid therapy.

Utility of pancreatography for diagnosing autoimmune pancreatitis

AIM: To identify pancreatographic findings that facilitate differentiating between autoimmune pancreatitis (AIP) and pancreatic cancer (PC) on endoscopic retrograde cholangiopancreatography (ERCP) and magnetic resonance cholangiopancreatography (MRCP).

METHODS: ERCP findings of 48 AIP and 143 PC patients were compared. Diagnostic accuracies for AIP by ERCP and MRCP were compared in 30 AIP patients.

RESULTS: The following ERCP findings suggested a diagnosis of AIP rather than PC. Obstruction of the main pancreatic duct (MPD) was more frequently detected in PC (P < 0.001). Skipped MPD lesions were detected only in AIP (P < 0.001). Side branch derivation from the narrowed MPD was more frequent in AIP (P < 0.001). The narrowed MPD was longer in AIP (P < 0.001), and a narrowed MPD longer than 3 cm was more frequent in AIP (P < 0.001). Maximal diameter of the upstream MPD was smaller in AIP (P < 0.001), and upstream dilatation of the MPD less than 5 mm was more frequent in AIP (P < 0.001). Stenosis of the lower bile duct was smooth in 87% of AIP and irregular in 65% of PC patients (P < 0.001). Stenosis of the intrahepatic or hilar bile duct was detected only in AIP (P = 0.001). On MRCP, diffuse narrowing of the MPD on ERCP was shown as a skipped non-visualized lesion in 50% and faint visualization in 19%, but segmental narrowing of the MPD was visualized faintly in only 14%.

CONCLUSION: Several ERCP findings are useful for differentiating AIP from PC. Although MRCP cannot replace ERCP for the diagnostic evaluation of AIP, some MRCP findings support the diagnosis of AIP.