Autoimmune pancreatitis: differentiation from pancreatic carcinoma and normal pancreas on the basis of enhancement characteristics at dual-phase CT. AJR Am J Roentgenol. 2009;193:479-484. [PMID: 19620446 DOI: 10.2214/ajr.08.1883]

Diagnostic performance of F-18 FDG PET/CT in differentiating autoimmune pancreatitis from pancreatic cancer: a systemic review and meta-analysis

OBJECTIVES

This study aims to evaluate the utility of F-18 FDG PET/CT in the non-invasive diagnosis of autoimmune pancreatitis (AIP) and differentiating it from pancreatic cancer (CaP) based on the amount and pattern of FDG uptake, as well as involvement of extra-pancreatic sites.

METHODS

A systematic search was conducted using PubMed, Scopus, Cochrane Library and Google Scholar. Only those studies that compared the findings of F-18 FDG PET/CT in terms of SUVmax, pattern of FDG uptake and presence of FDG-avid extra-pancreatic sites in both AIP and CaP were included. Studies were qualitatively assessed for risk of bias and publication bias. The diagnostic performance of parameters on PET/CT was examined through pooled sensitivity, specificity, diagnostic odd's ratio (DOR) and summary receiver operator characteristic (SROC) curve analysis.

RESULTS

Six studies were included with a total of 580 patients. 178 patients had AIP (Age 18-90 years, male, M: female, F ratio-8.4:1) and 402 patients had CaP (Age 22-88 years, M:F ratio-1.5:1). Type of AIP was reported in only 3 studies, with the included cases predominantly being type 1 AIP. All studies were retrospective with heterogeneity and a risk on patient selection and index test. The FDG uptake, expressed as SUVmax, was lower in AIP with a weighted mean difference of -3.11 (95% confidence interval, CI: -5.28 to -0.94). To diagnose AIP, the pooled sensitivity, specificity and DOR of diffuse pattern of FDG uptake were 0.59 (95% CI: 0.51-0.66), 0.89 (95% CI: 0.86-0.92) and 21.07 (95% CI: 5.07-88.32), respectively, with an area under curve (AUC) of 0.717 on SROC analysis. The pooled sensitivity, specificity and DOR of FDG-avid extra pancreatic sites were 0.55 (95% CI: 0.45-0.65), 0.58 (95% CI: 0.52-0.64) and 2.33 (95% CI: 1.40-3.89), respectively, with an AUC of 0.632.

CONCLUSION

On F-18 FDG PET/CT, a pancreatic lesion of AIP has a lower SUVmax value than CaP. A diffuse pattern of FDG uptake and presence of an extra-pancreatic FDG-avid site are nearly 21 times and twice more likely in AIP than CaP, respectively.

Cross-sectional imaging of pancreatic leak: a pictorial review

Pancreatic leaks occur when a disruption in the pancreatic ductal system results in the leakage of pancreatic enzymes such as amylase, lipase, and proteases into the abdominal cavity. While often associated with pancreatic surgical procedures, trauma and necrotizing pancreatitis are also common culprits. Cross-sectional imaging, particularly computed tomography, plays a crucial role in assessing postoperative conditions and identifying both early and late complications, including pancreatic leaks. The presence of fluid accumulation or hemorrhage near an anastomotic site strongly indicates a pancreatic fistula, particularly if the fluid is connected to the pancreatic duct or anastomotic suture line. Pancreatic fistulas are a type of pancreatic leak that carries a high morbidity rate. Early diagnosis and assessment of pancreatic leaks require vigilance and an understanding of its imaging hallmarks to facilitate prompt treatment and improve patient outcomes. Radiologists must maintain vigilance and understand the imaging patterns of pancreatic leaks to enhance diagnostic accuracy. Ongoing improvements in surgical techniques and diagnostic approaches are promising for minimizing the prevalence and adverse effects of pancreatic fistulas. In this pictorial review, our aim is to facilitate for radiologists the comprehension of pancreatic leaks and their essential imaging patterns.

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.

Autoimmune pancreatitis: Cornerstones and future perspectives

Autoimmune pancreatitis (AIP) is an autoimmune subtype of chronic pancreatitis resulting from the aberrant immune response against the pancreas, leading to inflammation and fibrosis. Although AIP is rare, its incidence is increasing and is often misdiagnosed as other pancreatic diseases. AIP is commonly classified into two types. Type 1 AIP (AIP-1) is typically associated with elevated serum immunoglobulin G4 (IgG4) levels and systemic manifestations, while type 2 AIP is typically a more localized form of the disease, and may coexist with other autoimmune disorders, especially inflammatory bowel diseases. Additionally, there is emerging recognition of a third type (type 3 AIP), which refers to immunotherapy-triggered AIP, although this classification is still gaining acceptance in medical literature. The clinical manifestations of AIP mainly include painless jaundice and weight loss. Elevated serum IgG4 levels are particularly characteristic of AIP-1. Diagnosis relies on a combination of clinical, laboratory, radiological, and histological findings, given the similarity of AIP symptoms to other pancreatic disorders. The mainstay of treatment for AIP is steroid therapy, which is effective in most cases. Severe cases might require additional imm-unosuppressive agents. This review aims to summarize the current knowledge of AIP, encompassing its epidemiology, etiology, clinical presentation, diagnosis, and treatment options. We also address the challenges and controversies in diagnosing and treating AIP, such as distinguishing it from pancreatic cancer and managing long-term treatment, highlighting the need for increased awareness and knowledge of this complex disease.

[Autoimmune pancreatitis versus pancreatic cancer]

CLINICAL ISSUE

Autoimmune pancreatitis (AIP) is classified as a distinct form of pancreatitis according to the guidelines. It is characterized by imaging morphologic and histologic features and is associated with extrapancreatic manifestations in type 1 IgG 4-associated disease. Symptoms and findings almost always improve with administration of steroids. Differentiation from pancreatic ductal adenocarcinoma is required, particularly in the presence of AIP with focal parenchymal involvement.

STANDARD RADIOLOGIC PROCEDURES

If AIP is suspected, abdominal ultrasound and/or endosonography, computed tomography (CT), and preferably magnetic resonance imaging (MRI) are indicated. A distinction is made between parenchymal and ductal changes that specifically indicate the presence of AIP.

METHODOLOGICAL INNOVATIONS AND EVALUATION

The diagnosis of autoimmune pancreatitis should be made based on the International Consensus Criteria (ICDC), in which the five main features (imaging, serology, histology, other organ involvement, response to steroid medication) are assessed. In type 1 AIP, typical imaging changes are sufficient to establish the diagnosis even with negative histology, whereas for type 2 AIP, histologic evidence is required. Imaging changes help in the differential diagnosis from pancreatic cancer.

PRACTICAL RECOMMENDATIONS

The following article addresses and evaluates crucial imaging diagnostic CT and MRI criteria for correct classification of findings, description of results, and differentiation of autoimmune pancreatitis from pancreatic cancer.

Pancreatic Cancer and Its Mimics

Pancreatic ductal adenocarcinoma (PDAC) is the most common primary pancreatic malignancy, ranking fourth in cancer-related mortality in the United States. Typically, PDAC appears on images as a hypovascular mass with upstream pancreatic duct dilatation and abrupt duct cutoff, distal pancreatic atrophy, and vascular encasement, with metastatic involvement including lymphadenopathy. However, atypical manifestations that may limit detection of the underlying PDAC may also occur. Atypical PDAC features include findings related to associated conditions such as acute or chronic pancreatitis, a mass that is isointense to the parenchyma, multiplicity, diffuse tumor infiltration, associated calcifications, and cystic components. Several neoplastic and inflammatory conditions can mimic PDAC, such as paraduodenal "groove" pancreatitis, autoimmune pancreatitis, focal acute and chronic pancreatitis, neuroendocrine tumors, solid pseudopapillary neoplasms, metastases, and lymphoma. Differentiation of these conditions from PDAC can be challenging due to overlapping CT and MRI features; however, certain findings can help in differentiation. Diffusion-weighted MRI can be helpful but also can be nonspecific. Accurate diagnosis is pivotal for guiding therapeutic planning and potential outcomes in PDAC and avoiding biopsy or surgical treatment of some of these mimics. Biopsy may still be required for diagnosis in some cases. The authors describe the typical and atypical imaging findings of PDAC and features that may help to differentiate PDAC from its mimics. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Zins in this issue.

Radiological parameters to predict pancreatic texture: Current evidence and future perspectives

Preoperative prediction of the postoperative pancreatic fistula risk is critical in the current era of minimally invasive pancreatic surgeries to tailor perioperative management, thereby minimizing postoperative morbidity. Pancreatic duct diameter can be readily measured by any routine imaging used to diagnose pancreatic disease. However, radiological evaluation of pancreatic texture, an important determinant of pancreatic fistula, has not been widely used to predict the risk of postoperative pancreatic fistula. Qualitative and quantitative assessment of pancreatic fibrosis and fat fraction provides the basis for predicting pancreatic texture. Traditionally computed tomography has been utilized in identifying and characterizing pancreatic lesions and background parenchymal pathologies. With the increasing utilisation of endoscopic ultrasound and magnetic resonance imaging for evaluating pancreatic pathologies, elastography is emerging as a promising tool for predicting pancreatic texture. Also, recent studies have shown that early surgery for chronic pancreatitis is associated with better pain relief and preservation of pancreatic function. Pancreatic texture assessment can allow early diagnosis of chronic pancreatitis, facilitating early intervention. The present review outlines the current evidence in utilizing various imaging modalities for determining the pancreatic texture based on different parameters and image sequences. However, multidisciplinary investigations using strong radiologic-pathologic correlation are needed to standardize and establish the role of these non-invasive diagnostic tools in predicting pancreatic texture.

Systematic review and meta-analysis of MRI features for differentiating autoimmune pancreatitis from pancreatic adenocarcinoma

OBJECTIVES

To identify reliable MRI features for differentiating autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC) and to summarize their diagnostic accuracy.

METHODS

We conducted a systematic literature review and meta-analysis using PubMed, EMBASE, and the Cochrane Library to identify original articles published between January 2006 and July 2021. The pooled diagnostic accuracy, including the diagnostic odds ratios (DORs) with 95% confidence intervals (CIs) of the identified features, was calculated using a bivariate random effects model.

RESULTS

Twelve studies were included, and 92 overlapping descriptors were subsumed under 16 MRI features. Ten features favoring AIP were diffuse enlargement (DOR, 75; 95% CI, 9-594), capsule-like rim (DOR, 52; 95% CI, 20-131), multiple main pancreatic duct (MPD) strictures (DOR, 47; 95% CI, 17-129), homogeneous delayed enhancement (DOR, 46; 95% CI, 21-104), low apparent diffusion coefficient value (DOR, 30), speckled enhancement (DOR, 30), multiple pancreatic masses (DOR, 29), tapered narrowing of MPD (DOR, 15), penetrating duct sign (DOR, 14), and delayed enhancement (DOR, 13). Six features favoring PDAC were target type enhancement (DOR, 41; 95% CI, 11-158), discrete pancreatic mass (DOR, 35; 95% CI, 15-80), upstream MPD dilatation (DOR, 13), peripancreatic fat infiltration (DOR, 10), upstream parenchymal atrophy (DOR, 5), and vascular involvement (DOR, 3).

CONCLUSION

This study identified 16 informative MRI features to differentiate AIP from PDAC. Among them, diffuse enlargement, capsule-like rim, multiple MPD strictures, and homogeneous delayed enhancement favored AIP with the highest DORs, whereas discrete mass and target type enhancement favored PDAC.

KEY POINTS

• The MRI features with the highest pooled diagnostic odds ratios (DORs) for autoimmune pancreatitis were diffuse enlargement of the pancreas (75), capsule-like rim (52), multiple strictures of the main pancreatic duct (47), and homogeneous delayed enhancement (46). • The MRI features with the highest pooled DORs for pancreatic ductal adenocarcinoma were target type enhancement (41) and discrete pancreatic mass (35).

Diffuse Involvement of Pancreas is not Always Autoimmune Pancreatitis

RATIONALE AND OBJECTIVES

To determine the prevalence of diffuse involvement of pancreas and to identify the findings of malignancies using enhancement computed tomography (CT).

MATERIALS AND METHODS

A total of 1,0249 patients performed enhancement CT in our hospital over 62 months were investigated and the final study cohort includes 245 patients (170 males, 75 females; mean age, 56.94 ± 12.17 years). The reference standard is the final clinical/pathological diagnosis. The lesion-to-aorta enhancement ratio (LAR) on the pancreatic arterial phase, portal phase and delayed phase (DP) and the traditional CT findings were evaluated. Intergroup comparisons between malignancies and non-malignancies lesions were performed. Univariate and multivariate analyses were conducted to identify findings predicting malignancies.

RESULTS

The prevalence of malignancy was 45.3% (111/245) of diffuse enlargement of pancreas. All benign lesions were autoimmune pancreatitis 54.7% (n = 134). The most common malignant lesion was pancreatic ductal adenocarcinoma (n = 88, 35.9%). Other rare lesions with malignant potential included pancreatic neuroendocrine tumor (n = 11, 4.5%), lymphoma (n = 4, 1.6%), metastasis (n = 4, 1.6%), solid pseudopapillary neoplasm (n = 3, 1.2%) and acinar cell carcinoma (n = 1, 0.4%). Residual normal pancreas parenchyma, heterogeneity, short axis (cut-off value, 3.15 cm) and LARDP (cut-off value, 0.75) were independent predictors of malignancies. When the above predictors were combined, a sensitivity of 94.2%, a specificity of 90.8% were attained.

CONCLUSION

Diffuse involvement of the pancreas is rare and is not a specific sign of autoimmune pancreatitis, and it is associated with a wide spectrum of malignant conditions. Dynamic enhancement CT is helpful to identifying malignancies.

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.

Nonfunctional pancreatic neuroendocrine tumours misdiagnosed as autoimmune pancreatitis: A case report and review of literature

BACKGROUND

Nonfunctional pancreatic neuroendocrine tumours are difficult to diagnose in the early stage of disease due to a lack of clinical symptoms, but they can rarely manifest as autoimmune pancreatitis. Autoimmune pancreatitis is an uncommon disease that may cause recurrent acute pancreatitis and is therefore often regarded as a special type of chronic pancreatitis.

CASE SUMMARY

We report a case of a 42-year-old female who had nonspecific upper abdominal pain for 4 years and radiological abnormalities of the pancreas that mimicked autoimmune pancreatitis. The symptoms and pancreatic imaging did not improve following 1 year of steroid therapy. Finally, pancreatic biopsy was performed through endoscopic ultrasonography-guided fine-needle aspiration biopsy, and nonfunctional pancreatic neuroendocrine tumours were ultimately diagnosed. Pancreatectomy has resolved her symptoms.

CONCLUSION

Therefore, the differentiation of nonfunctional pancreatic neuroendocrine tumours from autoimmune pancreatitis is very important, although it is rare. We propose that endoscopic ultrasonography-guided fine-needle aspiration biopsy should be performed if imaging characteristics are equivocal or the diagnosis is in question.

Application of dynamic contrast enhanced ultrasound in distinguishing focal-type autoimmune pancreatitis from pancreatic ductal adenocarcinoma

OBJECTIVE

To explore the value of dynamic contrast enhanced ultrasound (DCE-US) in preoperative differential diagnosis of focal-type autoimmune pancreatitis (AIP) and pancreatic ductal adenocarcinoma (PDAC).

PATIENTS AND METHODS

From May 2016 to March 2020, patients with biopsy and histopathologically confirmed focal-type AIP (n = 9) were retrospectively included. All patients received contrast enhanced ultrasound (CEUS) examinations one week before surgery/biopsy. Dynamic analysis was performed by VueBox® software (Bracco, Italy). Eighteen cases of resection and histopathologically proved PDAC lesions were also included as control group. B mode ultrasound (BMUS) features, CEUS enhancement patterns, time intensity curves (TICs) and CEUS quantitative parameters were obtained and compared between AIP and PDAC lesions.

RESULTS

After injection of ultrasound contrast agents, most focal-type AIP lesions displayed hyper-enhancement (2/9, 22.2%) or iso-enhancement (6/9, 66.7%) during arterial phase of CEUS, while most of PDAC lesions showed hypo-enhancement (88.9%) (P < 0.01). During late phase, most of AIP lesions showed iso-enhancement (8/9, 88.9%), while most of PDAC lesions showed hypo-enhancement (94.4%) (P < 0.001). Compared with PDAC lesions, TICs of AIP lesions showed delayed and higher enhancement. Among all CEUS perfusion parameters, ratio of PE (peak enhancement), WiAUC (wash-in area under the curve), WiR (wash-in rate), WiPI (wash-in perfusion index, WiPI = WiAUC/ rise time), WoAUC (wash-out area under the curve), WiWoAUC (wash-in and wash-out area under the curve) and WoR (wash-out rate) between pancreatic lesion and surrounding normal pancreatic tissue were significantly higher in AIP lesions than PDAC lesions (P < 0.05).

CONCLUSION

DCE-US with quantitative analysis has the potential to make preoperative differential diagnosis between focal-type AIP and PDAC non-invasively.

Use of MRI signal intensity ratio to differentiate between autoimmune pancreatitis and pancreatic ductal adenocarcinoma

AIM

To evaluate the accuracy of the lesion-to-erector spinae signal intensity ratio (SIR) on magnetic resonance imaging (MRI) for distinguishing autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDA).

MATERIALS AND METHODS

The MRI data of 21 patients with AIP and 27 patients with PDA were analysed retrospectively, and the signal intensity in pancreatic lesions and erector spinae muscles at the same level on T2-weighted imaging (T2WI), arterial phase (AP) imaging, and delayed phase (DP) imaging was measured for calculation of SIRs.

RESULTS

The mean SIRs of the pancreatic lesions and erector spinae from T2WI, AP, and DP images of AIP patients were 0.96, 1.27, and 1.42, respectively, while those of PDA patients were 1.35, 0.80, and 0.91, respectively. The differences in the SIRs between the AIP and PDA groups were statistically significant (p<0.001), with corresponding area under curve (AUC) values of 0.925, 0.906, and 0.961, respectively. The optimal cut-off values for the SIRs on T2WI, AP and DP images were 1.21, 1.01, and 1.08, respectively. SIR values < 1.21 on T2WI, >1.01 on AP imaging, and >1.08 on DP imaging identified AIP with sensitivities of 85.7%, 90.5%, and 90.5%, respectively, and specificities of 81.5%, 74.6%, and 81.5%, respectively. The AUC values for SIRs did not differ significantly between T2WI and DP imaging or AP and DP imaging (Z = 0.778, p=0.436; Z = 1.279, p=0.201).

CONCLUSION

The SIRs of pancreatic lesions and erector spinae on T2WI, AP, and DP images can be used to differentiate AIP from PDA.

Type 2 Autoimmune Pancreatitis: Consensus and Controversies

Autoimmune pancreatitis (AIP) has attracted much attention in the last two decades, and due to the diagnostic value of immunoglobulin G4 (IgG4), the number of cases diagnosed in clinical practice has markedly increased. However, in contrast to prototypic IgG4-related type 1 AIP, a minor subtype of AIP, referred to as type 2 AIP, is less widely known and has thus not yet been characterized in detail. Type 2 AIP is unrelated to IgG4 and is a completely distinct entity from type 1 AIP. One confusing factor is that the two types of AIP share patterns of clinical presentation (e.g., acute pancreatitis and painless jaundice) and imaging abnormalities (e.g., diffuse or segmental enlargement). Since there are currently no established serum markers, the diagnosis of type 2 AIP is highly challenging and requires the tissue confirmation of neutrophilic injury to the pancreatic ducts, a finding designated as a granulocytic epithelial lesion. Approximately one-third of cases are associated with inflammatory bowel disease, particularly ulcerative colitis; however, the pathological relationship between these two conditions has not yet been clarified. Unanswered questions relate to its pathophysiology, the potential development of a similar granulocytic injury in other organs, and the characteristics of pediatric cases. This review summarizes consensus and controversies surrounding type 2 AIP, with the aim of increasing awareness and highlighting the unmet needs of this underrecognized condition.

Evaluation of the contour of the pancreas: types and frequencies

PURPOSE

Pancreas contour variations can sometimes be misdiagnosed as mass lesions. This study aimed to evaluate normal pancreatic contour morphology, variations, frequency and the development of the uncinate process.

METHODS

Out of 1183 consecutive computed tomography images taken in our hospital for various reasons (e.g. malignity, donor), 899 suitable images were included in the study. The following variations were identified: globular, elongated or globular-elongated contours of the pancreas head, protrusions of the body-tail surfaces and globular, lobular, globular-lobular, tapered and bifid contours of the tail. Hypoplasia and aplasia of the uncinate process were identified. All images were evaluated retrospectively by two radiologists.

RESULTS

Of the 899 patients, 504 (56.1%) were males. The mean age of the patients was 53.9 ± 14.7 (range 18-89). Hypoplasia of the uncinate process was found in 72 (8%) patients; aplasia was seen in 11 (1.2%) patients. Thirty-one (3.5%) of the pancreatic head variations were globular, 49 (5.4%) elongated and three (0.3%) elongated-globular. In patients with pancreatic uncinate process developmental anomaly, contour variations were also detected in the head of the pancreas. The pancreatic body-tail showed protrusions anteriorly in 76 (8%) patients and posteriorly in 11 (1.2%) patients. Seventy-two (8%) of the pancreatic tail variations were globular, 39 (4.4%) were globular-lobular, 18 (2%) were tapered and 17 (1.8%) were bifid.

CONCLUSION

Patients with pancreatic uncinate process developmental anomaly also have contour variations in the head of the pancreas. Pancreatic uncinate process developmental anomaly was seen in 9.2%. Pancreatic tail contour variation was 16.2%. The pancreatic body-tail showed protrusion in 9.2% of patients.

Utilisation of artificial intelligence for the development of an EUS-convolutional neural network model trained to enhance the diagnosis of autoimmune pancreatitis

OBJECTIVE

The diagnosis of autoimmune pancreatitis (AIP) is challenging. Sonographic and cross-sectional imaging findings of AIP closely mimic pancreatic ductal adenocarcinoma (PDAC) and techniques for tissue sampling of AIP are suboptimal. These limitations often result in delayed or failed diagnosis, which negatively impact patient management and outcomes. This study aimed to create an endoscopic ultrasound (EUS)-based convolutional neural network (CNN) model trained to differentiate AIP from PDAC, chronic pancreatitis (CP) and normal pancreas (NP), with sufficient performance to analyse EUS video in real time.

DESIGN

A database of still image and video data obtained from EUS examinations of cases of AIP, PDAC, CP and NP was used to develop a CNN. Occlusion heatmap analysis was used to identify sonographic features the CNN valued when differentiating AIP from PDAC.

RESULTS

From 583 patients (146 AIP, 292 PDAC, 72 CP and 73 NP), a total of 1 174 461 unique EUS images were extracted. For video data, the CNN processed 955 EUS frames per second and was: 99% sensitive, 98% specific for distinguishing AIP from NP; 94% sensitive, 71% specific for distinguishing AIP from CP; 90% sensitive, 93% specific for distinguishing AIP from PDAC; and 90% sensitive, 85% specific for distinguishing AIP from all studied conditions (ie, PDAC, CP and NP).

CONCLUSION

The developed EUS-CNN model accurately differentiated AIP from PDAC and benign pancreatic conditions, thereby offering the capability of earlier and more accurate diagnosis. Use of this model offers the potential for more timely and appropriate patient care and improved outcome.

Proposal of a Preoperative CT-Based Score to Predict the Risk of Clinically Relevant Pancreatic Fistula after Cephalic Pancreatoduodenectomy

Background and Objectives: Postoperative pancreatic fistula after cephalic pancreatoduodenectomy (CPD) is still the leading cause of postoperative morbidity, entailing long hospital stay and costs or even death. The aim of this study was to propose the use of morphologic parameters based on a preoperative multisequence computer tomography (CT) scan in predicting the clinically relevant postoperative pancreatic fistula (CRPF) and a risk score based on a multiple regression analysis. Materials and Methods: For 78 consecutive patients with CPD, we measured the following parameters on the preoperative CT scans: the density of the pancreas on the unenhanced, arterial, portal and delayed phases; the unenhanced density of the liver; the caliber of the main pancreatic duct (MPD); the preoperatively estimated pancreatic remnant volume (ERPV) and the total pancreatic volume. We assessed the correlation of the parameters with the clinically relevant pancreatic fistula using a univariate analysis and formulated a score using the strongest correlated parameters; the validity of the score was appreciated using logistic regression models and an ROC analysis. Results: When comparing the CRPF group (28.2%) to the non-CRPF group, we found significant differences of the values of unenhanced pancreatic density (UPD) (44.09 ± 6.8 HU vs. 50.4 ± 6.31 HU, p = 0.008), delayed density of the pancreas (48.67 ± 18.05 HU vs. 61.28 ± 16.55, p = 0.045), unenhanced density of the liver (UDL) (44.09 ± 6.8 HU vs. 50.54 ± 6.31 HU, p = 0.008), MPD (0.93 ± 0.35 mm vs. 3.14 ± 2.95 mm, p = 0.02) and ERPV (46.37 ± 10.39 cm³ vs. 34.87 ± 12.35 cm³, p = 0.01). Based on the odds ratio from the multiple regression analysis and after calculating the optimum cut-off values of the variables, we proposed two scores that both used the MPD and the ERPV and differing in the third variable, either including the UPD or the UDL, producing values for the area under the receiver operating characteristic curve (AUC) of 0.846 (95% CI 0.694-0.941) and 0.774 (95% CI 0.599-0.850), respectively. Conclusions: A preoperative CT scan can be a useful tool in predicting the risk of clinically relevant pancreatic fistula.

Comparison of five-phase computed tomography images of type 1 autoimmune pancreatitis and pancreatic cancer: Emphasis on cases with atypical images

BACKGROUND/OBJECTIVES

International consensus diagnostic criteria (ICDC) include characteristic images of autoimmune pancreatitis (AIP); however, reports on atypical cases are increasing. The aims of this study were to compare CT findings between AIP and pancreatic cancer (PC), and to analyze type 1 AIPs showing atypical images.

METHODS

Five-phase CT images were compared between 80 type 1-AIP lesions and 80 size- and location-matched PCs in the case-control study. Atypical AIPs were diagnosed based on the four ICDC items.

RESULTS

ICDC items were recognized in most AIP lesions; pancreatic enlargement (87.7%), narrowing of the main pancreatic duct (98.8%), delayed enhancement (100%), and no marked upstream-duct dilation (97.5%). CT values of AIPs increased rapidly until the pancreatic phase and decreased afterward, while those of PCs gradually increased until the delayed phase (P < 0.0001). Atypical images were recognized in 14.8% of AIPs, commonly without pancreatic enlargement (18.5 mm) and sometimes mimicking intraductal neoplasms. The CT values and their ratios were different between atypical AIPs and size-matched PCs most significantly in the pancreatic phase, but similar in the delayed phase.

CONCLUSIONS

Ordinary type 1 AIPs can be diagnosed with the ICDC, but atypical AIPs represented a small fraction. "Delayed enhancement" is characteristic to ordinary AIPs, however, "pancreatic-phase enhancement" is more diagnostic for atypical AIPs.

Meta-analysis of CT and MRI for differentiation of autoimmune pancreatitis from pancreatic adenocarcinoma

OBJECTIVES

To systematically determine the diagnostic performance of computed tomography (CT) and magnetic resonance imaging (MRI) for differentiating autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC), with a comparison between the two imaging modalities.

METHODS

Literature search was conducted using PubMed and EMBASE databases to identify original articles published between 2009 and 2019 reporting the diagnostic performance of CT and MRI for differentiating AIP from PDAC. The meta-analytic sensitivity and specificity of CT and MRI were calculated, and compared using a bivariate random effects model. Subgroup analysis for differentiating focal AIP from PDAC was performed.

RESULTS

Of the 856 articles screened, 11 eligible articles are remained, i.e., five studies for CT, four for MRI, and two for both. The meta-analytic summary sensitivity and specificity of CT were 59% (95% confidence interval [CI], 41-75%) and 99% (95% CI, 88-100%), respectively, while those of MRI were 84% (95% CI, 68-93%) and 97% (95% CI, 87-99%). MRI had a significantly higher meta-analytic summary sensitivity than CT (84% vs. 59%, p = 0.02) but a similar specificity (97% vs. 99%, p = 0.18). In the subgroup analysis for focal AIP, the sensitivity for distinguishing between focal AIP and PDAC was lower than that for the overall analysis. MRI had a higher sensitivity than CT (76% vs. 50%, p = 0.28) but a similar specificity (97% vs. 98%, p = 0.07).

CONCLUSION

MRI might be clinically more useful to evaluate patients with AIP, particularly for differentiating AIP from PDAC.

KEY POINTS

• MRI had an overall good diagnostic performance to differentiate AIP from PDAC with a meta-analytic summary estimate of 83% for sensitivity and of 97% for specificity. • CT had a very high specificity (99%), but a suboptimal sensitivity (59%) for differentiating AIP from PDAC. • Compared with CT, MRI had a higher sensitivity, but a similar specificity.

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.

Autoimmune pancreatitis: an update

OBJECTIVE

Since the time of inception of autoimmune pancreatitis (AIP), our knowledge of autoimmune pancreatitis has expanded significantly. The aim of this review is to provide an update on clinical manifestations, diagnosis, imaging features, and treatment of AIP.

BACKGROUND AND CLINICAL SIGNIFICANCE

Type 1 AIP is the pancreatic manifestation of IgG4-related systemic disease, which can be diagnosed using a combination of clinical, histopathological, pancreatic imaging findings in conjunction with manifestation in other organs, as well of responsiveness to steroid treatment. It is vital to differentiate AIP from pancreatic cancer since both can mimic each other clinically and radiologically. Type 2 AIP is a rare but distinct subtype of AIP which occurs mostly in the younger patient.

CONCLUSION

AIP is steroid-responsive chronic pancreatitis with distinct manifestations on imaging.

Differentiating autoimmune pancreatitis from pancreatic ductal adenocarcinoma with CT radiomics features

PURPOSE

The purpose of this study was to determine whether computed tomography (CT)-based machine learning of radiomics features could help distinguish autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC).

MATERIALS AND METHODS

Eighty-nine patients with AIP (65 men, 24 women; mean age, 59.7±13.9 [SD] years; range: 21-83 years) and 93 patients with PDAC (68 men, 25 women; mean age, 60.1±12.3 [SD] years; range: 36-86 years) were retrospectively included. All patients had dedicated dual-phase pancreatic protocol CT between 2004 and 2018. Thin-slice images (0.75/0.5mm thickness/increment) were compared with thick-slices images (3 or 5mm thickness/increment). Pancreatic regions involved by PDAC or AIP (areas of enlargement, altered enhancement, effacement of pancreatic duct) as well as uninvolved parenchyma were segmented as three-dimensional volumes. Four hundred and thirty-one radiomics features were extracted and a random forest was used to distinguish AIP from PDAC. CT data of 60 AIP and 60 PDAC patients were used for training and those of 29 AIP and 33 PDAC independent patients were used for testing.

RESULTS

The pancreas was diffusely involved in 37 (37/89; 41.6%) patients with AIP and not diffusely in 52 (52/89; 58.4%) patients. Using machine learning, 95.2% (59/62; 95% confidence interval [CI]: 89.8-100%), 83.9% (52:67; 95% CI: 74.7-93.0%) and 77.4% (48/62; 95% CI: 67.0-87.8%) of the 62 test patients were correctly classified as either having PDAC or AIP with thin-slice venous phase, thin-slice arterial phase, and thick-slice venous phase CT, respectively. Three of the 29 patients with AIP (3/29; 10.3%) were incorrectly classified as having PDAC but all 33 patients with PDAC (33/33; 100%) were correctly classified with thin-slice venous phase with 89.7% sensitivity (26/29; 95% CI: 78.6-100%) and 100% specificity (33/33; 95% CI: 93-100%) for the diagnosis of AIP, 95.2% accuracy (59/62; 95% CI: 89.8-100%) and area under the curve of 0.975 (95% CI: 0.936-1.0).

CONCLUSIONS

Radiomic features help differentiate AIP from PDAC with an overall accuracy of 95.2%.

Type 2 Autoimmune Pancreatitis (Idiopathic Duct-Centric Pancreatitis) Highlighting Patients Presenting as Clinical Acute Pancreatitis: A Single-Center Experience

Background/Aims

Type 2 autoimmune pancreatitis (AIP) has been considered extremely rare in East Asia. This study aimed to clarify the prevalence, clinical characteristics and radiological findings of type 2 AIP highlighting patients presenting as acute pancreatitis in a single center.

Methods

Type 2 AIP patients were classified according to International Consensus Diagnostic Criteria. Radiological findings were compared between type 2 AIP presenting as acute pancreatitis and gallstone pancreatitis.

Results

Among 244 patients with AIP, 27 (11.1%) had type 2 AIP (definite, 15 [55.5%] and probable 12 [44.5%]). The median age of patients with type 2 AIP was 29 years (interquartile range, 20 to 39 years). Acute pancreatitis was the most common initial presentation (n=17, 63%) while obstructive jaundice was present in only one patient. Ulcerative colitis (UC) was associated with type 2 AIP in 44.4% (12/27) of patients. Radiological pancreatic imaging such as delayed enhancement of diffusely enlarged pancreas, homogeneous enhancement of focal enlargement/mass, absent/minimal peripancreatic fat infiltration or fluid collection, and multifocal main pancreatic duct narrowings were helpful for differentiating type 2 AIP from gallstone pancreatitis. During follow-up (median, 32.3 months), two patients (2/25, 8%) experienced relapse.

Conclusions

In South Korea, type 2 AIP is not as rare as previously thought. Overall, the clinical profile of type 2 AIP was similar to that of Western countries. Type 2 AIP should be considered in young UC patients with acute pancreatitis of uncertain etiology.

Pictorial Review of Rare Pancreatic Tumors and Tumor-Like Lesions

췌장에는 다양한 종류의 종양 및 종양 유사 병변들이 생길 수 있다. 이 가운데, 췌장선암은 췌장의 가장 흔한 종양으로서 일반적으로 췌장암이라고 하면 이 종양을 가리킨다. 최근에는 영상 검사의 기술적 진보와 이용이 증가하면서 췌장의 희귀 종양 및 종양 유사 병변들의 발견 빈도가 증가하고 있다. 췌장의 드문 종양 및 종양과 유사한 병변들은 치료 방침과 예후가 췌장선암과 다르기 때문에 이들 질환의 감별은 임상적으로 중요한 의의가 있다. 영상 검사는 포상세포암이나 신경초종 등의 희귀 종양 및 자가면역 췌장염 또는 염증성 거짓종양과 같은 종양 유사 병변들과 췌장선암의 감별 진단에 중요한 역할을 하지만 영상 소견만으로 이들 질환을 정확히 구분하는 것은 한계가 있다. 이 논문에서는 췌장에서 생길 수 있는 희귀 종양 및 종양 유사 병변들의 다양한 영상 소견들과 췌장선암과의 감별에 있어 도움이 되는 특징들을 제시하고자 한다.

A feasible CT feature to differentiate focal-type autoimmune pancreatitis from pancreatic ductal adenocarcinoma

BACKGROUND

To investigate whether the relative computed tomography (CT) value (rCT) of adjacent pancreatic parenchyma can distinguish focal-type autoimmune pancreatitis (fAIP) from pancreatic ductal adenocarcinoma (PDAC).

METHODS

A total of 13 patients with fAIP and 20 patients with PDAC were included in this study. The rCT was calculated as the ratio of the CT value of adjacent pancreatic parenchyma to that of muscle. The diagnostic performance of rCT for discriminating fAIP from PDAC was evaluated using receiver operating characteristic (ROC) analysis.

RESULTS

Both fAIP and PDAC presented hyper-fibrosis histologically and delayed enhancement on CT examination. Moreover, the pancreatic parenchyma of fAIP presented serious inflammation. The mean rCT of the parenchyma was significantly lower in fAIP than in PDAC in all phases. The best diagnostic performance of the rCT value was found in the pancreatic phase, with an area under the ROC curve of 0.912, while the areas under the ROC curve of the portal and delayed phases were 0.812 and 0.754, respectively. The optimal cut-off value for distinguishing fAIP from PDAC was 1.62 in the pancreatic phase.

CONCLUSIONS

The rCT of the pancreatic parenchyma during the pancreatic phase may be a feasible CT feature for differentiating fAIP from PDAC.

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.

Unclassified autoimmune pancreatitis mimicking pancreatic cancer

A 24-year-old black male presented with a 1-week obstructive jaundice and intermittent abdominal pain, with no significant weight loss and an unsuspicious abdominal exam. Blood chemistry showed a cholestatic pattern but a complete immunological and tumoral panel (anti-smooth muscle antibody, anti-mitochondrial antibody, anti-nuclear antibody, anti-neutrophil cytoplasmic antibody, anti-Smith, anti-double-stranded-DNA antibody (anti-dsDNA), complement C3/C4, carcinoembryonic antigen, CA 19-9 and IgG4) were all within normal limits. Abdominal ultrasound revealed dilatation of the intra and extra-hepatic bile ducts. CT scan showed an abnormal dilatation of the distal bile duct but no focal enlargement of the head of the pancreas. Endoscopic ultrasound suggested an inflammatory process but the magnetic resonance cholangio-pancreatography favored a neoplastic obstruction of the distal common bile duct. Fine-needle aspiration cytology was insufficient for definitive diagnosis and the patient underwent major surgery. Follow-up with mild exocrine pancreatic insufficiency treated with enzyme replacement.

Computed Tomography Enhancement Pattern of the Pancreatic Parenchyma Predicts Postoperative Pancreatic Fistula After Pancreaticoduodenectomy

OBJECTIVE

The aim of this study was to assess the relationship between the computed tomography (CT) pancreatic parenchyma attenuation value and clinically relevant postoperative pancreatic fistula (POPF).

METHODS

The medical records of 115 patients who underwent pancreaticoduodenectomy and preoperative dynamic CT were retrospectively reviewed. The CT attenuation values of the nonenhanced (N), arterial (A), portal venous (P), and late (L) phase in the pancreatic parenchyma were determined via CT, and the A/N, A/P, and P/L ratios were calculated. The CT attenuation values and value ratios were compared between the POPF and non-POPF groups.

RESULTS

Thirty-two patients (28%) were categorized in the POPF group. On univariate analysis, the A/P ratio (P < 0.001) and P/L ratio (P = 0.018) were significantly higher in the POPF group. On receiver operating characteristic curve analysis, the A/P and P/L ratio cutoff values for predicting POPF were 1.19 and 1.17, respectively. Of the preoperative evaluable factors, A/P ratio of 1.19 or greater (P < 0.001; odds ratio, 10.3) and P/L ratio of 1.17 or greater (P = 0.049; odds ratio, 3.23) were independent predictive factors for POPF, and the combination of the 2 ratios was useful in detecting POPF preoperatively.

CONCLUSIONS

The enhancement pattern of the pancreatic parenchyma is associated with the development of clinically relevant POPF.

Autoimmune Pancreatitis

Over the course of the last 2 decades our knowledge of autoimmune pancreatitis has increased exponentially. In this review, we summarize the clinical presentation, diagnosis and treatment of AIP, to better allow general gastroenterologists and primary care providers to consider AIP as a as a rare but important cause of painless obstructive jaundice and recurrent acute pancreatitis. While steroids remain the mainstay of first line therapy, a number of patients with type 1 AIP require immunomodulators or rituximab to maintain remission; recommendations on the management of relapses continue to evolve.

Multiple solid pancreatic lesions: Prevalence and features of non-malignancies on dynamic enhanced CT

OBJECTIVE

To determine the prevalence of multiple solid pancreatic lesions on dynamic enhanced CT performed for suspected pancreatic diseases, and to identify CT features of non-malignancies.

METHODS

We investigated 8096 consecutive patients who underwent dynamic enhanced CT pancreas protocol at a tertiary center over 40 months. The final clinical /pathological diagnosis served as reference standard. The diagnostic accuracy of dynamic enhanced CT for non-malignancies was calculated. A univariate and multivariate analysis was conducted to identify features that predict non-malignancies.

RESULTS

Multiple solid pancreatic lesions were identified in 121 patients. The prevalence of non-malignancies was 19.8% (24/121). The most common non-malignancy was autoimmune pancreatitis (n = 21; 17.4%). Common lesions with malignant potential included neuroendocrine neoplasia (n = 62; 51.2%), ductal adenocarcinoma (n = 15; 12.4%), metastasis (n = 9; 7.4%), and lymphoma (n = 7; 5.8%). Dynamic enhanced CT had a sensitivity of 79.2% and a specificity of 92.8% for diagnosing non-malignancies. Elevated serum IgG4 level (p < 0.001), hypo-enhancement in arterial phase (p = 0.001), hyper-enhancement in equilibrium phase (p = 0.009) and location in both proximal and distal pancreas (p = 0.036) were predictors of non-malignancies, whereas pancreatic duct morphology and vascular invasion status were not.

CONCLUSION

Multiple solid pancreatic lesions were rare, with a wide spectrum. Dynamic enhanced CT provides clues for identifying non-malignancies.

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.

Prediction of pancreatic fistula after pancreatoduodenectomy by preoperative dynamic CT and fecal elastase-1 levels

Objective

To validate preoperative dynamic CT and fecal elastase-1 level in predicting the development of pancreatic fistulae after pancreatoduodenectomy.

Materials and methods

For 146 consecutive patients, CT attenuation values of the nontumorous pancreatic parenchyma were retrospectively measured on precontrast, arterial and equilibrium phase images for calculation of enhancement ratios. CT enhancement ratios and preoperative fecal elastase-1 levels were correlated with the development of pancreatic fistulae using independent t-test, logistic regression models, ROC analysis, Youden method and tree analysis.

Results

The mean value of enhancement ratio on equilibrium phase was significantly higher (p = 0.001) in the patients without pancreatic fistula (n = 107; 2.26±3.63) than in the patients with pancreatic fistula (n = 39; 1.04±0.51); in the logistic regression analyses, it was significant predictor for the development of pancreatic fistulae (odds ratio = 0.243, p = 0.002). The mean preoperative fecal elastase-1 levels were higher (odds ratio = 1.003, p = 0.034) in the pancreatic fistula patients than other patients, but there were no significant differences in the areas under the curve between the prediction values of CT enhancement ratios and fecal elastase-1 combined and those of CT enhancement ratios alone (P = 0.897, p = 0.917) on ROC curve analysis. Tree analysis revealed that the CT enhancement ratio was more powerful predictor of pancreatic fistula than fecal elastase-1 levels.

Conclusion

The preoperative CT enhancement ratio of pancreas acquired at equilibrium phase regardless of combination with fecal elastase-1 levels might be a useful predictor of the risk of developing a pancreatic fistula following pancreatoduodenectomy.

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.

Autoimmune Pancreatitis: An Update on Diagnosis and Management

There is an evolving understanding that autoimmune pancreatitis (AIP) is an immunoglobulin (Ig) G4 systemic disease. It can manifest as primarily a pancreatic disorder or in association with other disorders of presumed autoimmune cause. Classic clinical characteristics include obstructive jaundice, abdominal pain, and acute pancreatitis. Thus, AIP can be difficult to distinguish from pancreatic malignancy. However, AIP may respond to therapy with corticosteroids, and has a strong association with other immune mediated diseases. Although primarily a pathologic diagnosis, attempts have been made to reliably diagnose AIP clinically. AIP can be classified as either type 1 or type 2.

A Simple Method to Evaluate Whether Pancreas Texture Can Be Used to Predict Pancreatic Fistula Risk After Pancreatoduodenectomy

INTRODUCTION

Soft pancreas is one of the most important risk factor for postoperative pancreatic fistula after pancreatoduodenectomy. The aim of this study is to investigate whether pancreatic attenuation index utilized to assess the pancreatic texture with computed tomography can be used to predict the risk of developing a clinically relevant postoperative pancreatic fistula after pancreatoduodenectomy.

METHODS

We reviewed 76 consecutive patients undergoing pancreatoduodenectomy between 2012 and 2014. The pancreatic attenuation index is found by dividing the pancreas density by the spleen density achieved with non-enhanced computed tomography. The independent predictors of clinically relevant postoperative pancreatic fistula were investigated.

RESULTS

Clinically relevant postoperative pancreatic fistula occurred in 13 patients (17.1%). The group of patients with postoperative pancreatic fistula is compared with the group of patients without postoperative pancreatic fistula in terms of age, gender, body mass index, the American Society of Anesthesiologists (ASA) score, smoking, alcohol consumption, medical comorbidities, preoperative biliary drainage, type of anastomosis, and pancreatic duct size and pancreatic attenuation index. Univariate analyses have shown a significant difference in relation to chronic obstructive pulmonary disease and pancreatic attenuation index. The multivariate analyses showed that only pancreatic attenuation index was associated with a high postoperative pancreatic fistula rate (P = 0.012).

CONCLUSION

A preoperative non-contrast computed tomography scan evaluating pancreatic attenuation index could help to predict the occurrence of clinically significant postoperative pancreatic fistula after pancreatoduodenectomy.

Pancreatic and Extrapancreatic Features in Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) accounts for approximately 5% of chronic pancreatitis cases and is an important consideration in the differential diagnosis of pancreatic pathologies. The underlying pathophysiology of AIP is thought to involve lymphocyte infiltration and associated sclerosis. Although AIP is a benign condition that is treatable with corticosteroids, it can have imaging and clinical findings indistinguishable from pancreatic cancer. As such, the radiologist plays an important management role in distinguishing AIP from more sinister conditions. In addition, there are several extrapancreatic imaging findings in the context of AIP that have been recently described. This pictorial review outlines both the pancreatic and extrapancreatic imaging features in AIP and the response to steroid therapy. Important imaging features that allow AIP to be differentiated from other pancreatic pathology, including adenocarcinoma, lymphoma, and acute pancreatitis will be discussed.

Recent Advances in Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis that is characterized clinically by frequent presentation with obstructive jaundice, histologically by a dense lymphoplasmacytic infiltrate with fibrosis, and therapeutically by a dramatic response to corticosteroid therapy. Two distinct diseases, type 1 and type 2 AIP, share these features. However, these 2 diseases have unique pancreatic histopathologic patterns and differ significantly in their demographic profiles, clinical presentation, and natural history. Recognizing the popular and long-standing association of the term "AIP" with what is now called "type 1 AIP," we suggest using "AIP" solely for type 1 AIP and to acknowledge its own distinct disease status by using "idiopathic duct-centric chronic pancreatitis" (IDCP) for type 2 AIP. AIP is the pancreatic manifestation of immunoglobulin G4-related disease (IgG4-RD). The etiopathogenesis of AIP and IgG4-RD is largely unknown. However, the remarkable effectiveness of B-cell depletion therapy with rituximab in patients with AIP and IgG4-RD highlights the crucial role of B cells in its pathogenesis. IDCP is less commonly recognized, and little is known about its pathogenesis. IDCP has no biomarker but is associated with inflammatory bowel disease in ~25% of patients. Recently, the international consensus diagnostic criteria for AIP identified combinations of features that are diagnostic of both diseases. Both AIP and IDCP are corticosteroid responsive; however, relapses are common in AIP and rare in IDCP. Therefore, maintenance therapy with either an immunomodulator (eg, azathioprine, 6-mercaptopurine, or mycophenolate mofetil) or rituximab is often necessary for patients with AIP. Long-term survival is excellent for both patients with AIP and patients with IDCP.

A mass in the junction of the body and tail of the pancreas with negative IgG4 serology: IgG4-related disease with negative serology

Patient:Female, 55

Final Diagnosis: Autoimmune pancreatitis

Symptoms: Abdominal pain • weight loss

Medication: Prednisone

Clinical Procedure: Admitted to the hospital

Specialty: Gastroenterology and Hepatology

Differentiation of focal-type autoimmune pancreatitis from pancreatic carcinoma: assessment by multiphase contrast-enhanced CT

OBJECTIVES

To evaluate the utility of multiphase contrast-enhanced computed tomography (CT) findings alone and in combination for differentiating focal-type autoimmune pancreatitis (f-AIP) from pancreatic carcinoma (PC).

METHODS

The study group comprised 22 f-AIP lesions and 61 PC lesions. Two radiologists independently evaluated CT findings. Frequencies of findings were compared between f-AIP and PC. Statistical, univariate and multivariate analyses were performed.

RESULTS

Homogeneous enhancement during the portal phase (AIP, 59 % vs. PC, 3 %; P < 0.001), dotted enhancement during the pancreatic phase (50 % vs. 7 %; P < 0.001), duct-penetrating sign (46 % vs. 2 %; P < 0.001), enhanced duct sign (36 % vs. 2 %; P < 0.001) and capsule-like rim (46 % vs. 3 %; P < 0.001) were more frequently observed in AIP. Ring-like enhancement during the delayed phase (5 % vs. 46 %; P < 0.001) and peripancreatic strands with a length of at least 10 mm (5 % vs. 39 %; P = 0.001) were more frequently observed in PC. AIP was identified with 82 % sensitivity and 98 % specificity using four of these seven findings. Multivariate analysis revealed significant differences in dotted enhancement (P = 0.004), duct-penetrating sign (P < 0.001) and capsule-like rim (P = 0.007).

CONCLUSIONS

The combination of CT findings may allow improvements in differentiating f-AIP from PC.

KEY POINTS

• f-AIP can mimic PC on imaging findings. • The differentiation of f-AIP from PC is important in patient management. • Some CT findings can be used to identify AIP. • The combination of CT findings will improve differentiation from PC.

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.

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.

The spectrum of IgG4-related disease in the abdomen and pelvis

OBJECTIVE

IgG4-related disease was not recognized as a specific clinical entity until 2003 when extrapancreatic lesions were reported in patients with autoimmune pancreatitis. IgG4-related disease is characterized by elevated serum IgG4 levels and infiltration of the target organ by IgG4-positive plasma cells. The complete gamut of visceral involvement is still being outlined. The purpose of this article is to highlight the plethora of lesions under the spectrum of IgG4-related disease of the abdomen and pelvis, describe their imaging appearances on multimodality cross-sectional imaging, and discuss the differential diagnoses.

CONCLUSION

It is important for radiologists to recognize the multiorgan involvement and few classic features of IgG4-related disease that often tend to simulate malignancy.

Focal autoimmune pancreatitis: Radiological characteristics help to distinguish from pancreatic cancer

AIM: To identify the radiological characteristics of focal autoimmune pancreatitis (f-AIP) useful for differentiation from pancreatic cancer (PC).

METHODS: Magnetic resonance imaging (MRI) and triple-phase computed tomography (CT) scans of 79 patients (19 with f-AIP, 30 with PC, and 30 with a normal pancreas) were evaluated retrospectively. A radiologist measured the CT attenuation of the pancreatic parenchyma, the f-AIP and PC lesions in triple phases. The mean CT attenuation values of the f-AIP lesions were compared with those of PC, and the mean CT attenuation values of pancreatic parenchyma in the three groups were compared. The diagnostic performance of CT attenuation changes from arterial phase to hepatic phase in the differentiation between f-AIP and PC was evaluated using receiver operating characteristic (ROC) curve analysis. We also investigated the incidence of previously reported radiological findings for differentiation between f-AIP and PC.

RESULTS: The mean CT attenuation values of f-AIP lesions in enhanced phases were significantly higher than those of PC (arterial phase: 60 ± 7 vs 48 ± 10, P < 0.05; pancreatic phase: 85 ± 6 vs 63 ± 15, P < 0.05; hepatic phase: 95 ± 7 vs 63 ± 13, P < 0.05). The mean CT attenuation values of f-AIP lesions were significantly lower those of uninvolved pancreas and normal pancreas in the arterial and pancreatic phase of CT (P < 0.001, P < 0.001), with no significant difference at the hepatic phase or unenhanced scanning (P = 0.4, P = 0.1). When the attenuation value increase was equal or more than 28 HU this was considered diagnostic for f-AIP, and a sensitivity of 87.5%, specificity of 100% and an area under the ROC curve of 0.974 (95%CI: 0.928-1.021) were achieved. Five findings were more frequently observed in f-AIP patients: (1) sausage-shaped enlargement; (2) delayed homogeneous enhancement; (3) hypoattenuating capsule-like rim; (4) irregular narrowing of the main pancreatic duct (MPD) and/or stricture of the common bile duct (CBD); and (5) MPD upstream dilation ≤ 5 mm.

CONCLUSION: Analysis of a combination of CT and MRI findings could improve the diagnostic accuracy of differentiating f-AIP from PC.

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.