Determination of steroid response by abdominal ultrasound in cases with autoimmune pancreatitis

Autoimmune Pancreatitis: A Review

Autoimmune pancreatitis is a rare condition of pancreatic inflammation with two classic subtypes. The emergence of a third subtype, ICI-induced pancreatitis, highlights the need for knowledge of each type to ensure accurate diagnosis and treatment. Abbreviations: AIP-Autoimmune pancreatitis; AIP-1-Type 1 autoimmune pancreatitis, also known as lymphoplasmacytic sclerosing pancreatitis (LPSP); AIP-2-Type 2 autoimmune pancreatitis, also referred to as idiopathic duct-centric pancreatitis (IDCP); AIP-3-Type 3 autoimmune pancreatitis, also known as immune checkpoint inhibitor (ICI)-induced autoimmune pancreatitis; IgG4-RD-Immunoglobulin G4-related disease.

Treatment Strategies for Chronic Pancreatitis (CP)

Chronic pancreatitis (CP) and autoimmune pancreatitis (AIP) are diseases with overlapping features, both requiring complex management strategies. CP is characterized by pancreatic exocrine insufficiency (PEI) and pain, with treatment focused on symptom relief through pancreatic enzyme replacement therapy (PERT), pain control, and lifestyle and nutritional changes. However, the standard therapy does not address the underlying inflammation or fibrosis, which drives disease progression. AIP, on the other hand, presents with obstructive jaundice and fibrosis and is classified into two subtypes: Type 1 (AIP-1), linked to IgG4-related disease, and Type 2 (AIP-2), associated with inflammatory bowel disease. Treatment for AIP typically involves oral steroids. Immunomodulators and rituximab are used for recurrent or refractory cases. Novel therapies targeting the inflammation and fibrotic components of CP are being explored. A multidisciplinary approach is essential to optimize care and improve patients' outcomes.

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.

Challenges for clinicians treating autoimmune pancreatitis: Current perspectives

Autoimmune pancreatitis (AIP) is a rare disease clinically characterized by obstructive jaundice, unintentional weight loss, acute pancreatitis, focal pancreatic mass, and diabetes. AIP is classified into two subtypes - type 1 and type 2 - according to pathological findings, clinical features, and serology test results, but some cases may be defined as type not otherwise in the absence of pathological findings and inflammatory bowel disease. To address the differences in diagnostic criteria by country, standard diagnostic criteria for AIP were proposed in 2011 by an international consensus of expert opinions. Differential diagnosis of AIP from pancreatic ductal adenocarcinoma is important but remains challenging for clinicians. Fortunately, all subtypes of AIP show dramatic response to steroid treatment. This review discusses the current perspectives on the diagnosis and management of AIP in clinical practice.

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.

Diagnostic and therapeutic considerations in biopsy-proven type 2 autoimmune pancreatitis: comparative analysis with biopsy-proven type 1 autoimmune pancreatitis

BACKGROUND

Autoimmune processes are now an increasingly recognized cause of acute and chronic pancreatitis. Autoimmune pancreatitis is a rare, benign pathology with two distinct clinicopathologic subtypes. The aim of this study was to compare the presentation, diagnostic considerations and outcomes of patients with biopsy-proven type 1 and 2 autoimmune pancreatitis (AIP).

METHODS

A retrospective review of the Queensland Health pathology database of histologically proven AIP was conducted. Parameters compared included demographics, diagnostic criterion and post-treatment outcomes.

RESULTS

Twenty-three patients had a confirmed histological diagnosis of AIP (type 1 = 13, type 2 = 10). Patients with type 2 AIP were younger (median age 49 versus 59 years, P < 0.05). There was no significant difference in gender distribution of disease at presentation. Type 2 AIP presented with significant increased focal pancreatic changes on cross-sectional imaging (80% versus 54%, P < 0.05). Serum IgG4 levels were raised (>1.40 g/L) in 69% of patients with type 1 AIP and not detected in type 2 (P < 0.01). Concurrent underlying inflammatory bowel disease was present in a higher proportion of type 2 AIP (40% versus 15%, P < 0.05). A significantly increased proportion of patients with type 2 AIP underwent surgical resection (70% versus 30%, P < 0.05). Conservative management was utilized in more patients with type 1 disease (54% versus 30%). On follow-up, two patients have experienced symptomatic relapse at 6-18 months.

CONCLUSIONS

Diagnostic challenges do exist and clinicians must suspect 2 type AIP in young, serum IgG4-negative inflammatory bowel disease patients with recurrent pancreatitis.

Steroid Therapy and Steroid Response in Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP), a unique subtype of pancreatitis, is often accompanied by systemic inflammatory disorders. AIP is classified into two distinct subtypes on the basis of the histological subtype: immunoglobulin G4 (IgG4)-related lymphoplasmacytic sclerosing pancreatitis (type 1) and idiopathic duct-centric pancreatitis (type 2). Type 1 AIP is often accompanied by systemic lesions, biliary strictures, hepatic inflammatory pseudotumors, interstitial pneumonia and nephritis, dacryoadenitis, and sialadenitis. Type 2 AIP is associated with inflammatory bowel diseases in approximately 30% of cases. Standard therapy for AIP is oral corticosteroid administration. Steroid treatment is generally indicated for symptomatic cases and is exceptionally applied for cases with diagnostic difficulty (diagnostic steroid trial) after a negative workup for malignancy. More than 90% of patients respond to steroid treatment within 1 month, and most within 2 weeks. The steroid response can be confirmed on clinical images (computed tomography, ultrasonography, endoscopic ultrasonography, magnetic resonance imaging, and 18F-fluorodeoxyglucose-positron emission tomography). Hence, the steroid response is included as an optional diagnostic item of AIP. Steroid treatment results in normalization of serological markers, including IgG4. Short- and long-term corticosteroid treatment may induce adverse events, including chronic glycometabolism, obesity, an immunocompromised status against infection, cataracts, glaucoma, osteoporosis, and myopathy. AIP is common in old age and is often associated with diabetes mellitus (33-78%). Thus, there is an argument for corticosteroid therapy in diabetes patients with no symptoms. With low-dose steroid treatment or treatment withdrawal, there is a high incidence of AIP recurrence (24-52%). Therefore, there is a need for long-term steroid maintenance therapy and/or steroid-sparing agents (immunomodulators and rituximab). Corticosteroids play a critical role in the diagnosis and treatment of AIP.

Type 1 Autoimmune Pancreatitis with Imaging Appearance Similar to That of Malignant Cystic Tumor

A 79-year-old man was admitted with asymptomatic elevation of liver enzymes and tumor markers. Abdominal contrast-enhanced computed tomography demonstrated swelling of the pancreatic head, and additional blood test showed raised IgG4 levels. Histological examination by endoscopic ultrasonography (EUS)-guided fine needle aspiration for pancreatic head mass revealed storiform fibrosis and IgG4-positive plasma cell infiltration. We diagnosed this case as type 1 autoimmune pancreatitis (AIP). In addition, there was a cystic lesion in the pancreatic body apart from the pancreatic head mass. A mural nodule in the multilocular cyst was detected by EUS, and there was positive uptake of fluorodeoxyglucose in positron emission tomography/magnetic resonance imaging. The preoperative diagnosis of this cystic lesion was intraductal papillary mucinous carcinoma, and distal pancreatomy was performed. Histopathological findings showed various sizes of retention cysts caused by IgG4-positive plasma cell infiltration around the pancreatic branch ducts. The mural nodule was a fibrotic mass with diffuse infiltration of IgG4-positive cells. This cystic lesion mimicking malignant cystic neoplasm occurred in relation to AIP. This case provided important information helping to understand the mechanism of formation of mural nodules in multilocular cysts in patients with type 1 AIP.

Autoimmune pancreatitis: Imaging features

BACKGROUND AND OBJECTIVES

Autoimmune pancreatitis (AIP) remains a difficult disease to diagnose before treatment, particularly if presenting as a focal mass lesion. The purpose of this multicenter retrospective study is to analyze imaging features of histologically confirmed AIP to determine the additional diagnostic value of contrast-enhanced ultrasound (CEUS), contrast-enhanced endoscopic ultrasound (CE-EUS), and elastography to B-mode features.

PATIENTS AND METHODS

We report on a retrospective data collection of 60 histologically confirmed cases of AIP in comparison to 16 patients with pancreatic adenocarcinomas (PDAC). All CE (-E) US examinations were assessed by two independent readers in consensus. The role of CEUS and CE-EUS for pancreatic evaluation was defined according to the 2011 European Federation of Societies for Ultrasound in Medicine and Biology guidelines.

RESULTS

After injection of ultrasound (US) contrast agents, most AIP lesions displayed focal or diffuse isoenhancement (86.6%) in the arterial phase, while most of the PDAC lesions (93.7%) were hypoenhancing (P < 0.01). During the late phase, most AIP lesions were hyper-(65%) or iso-enhancing (35%), while most PDAC lesions were hypoenhancing (93.7%). CE-EUS was performed in a subset of ten patients and showed hyperenhancement in all AIP cases. Most focal AIP lesions (n = 27, 79.4%) were stiffer than the surrounding pancreatic parenchyma.

CONCLUSIONS

In this study, percutaneous and endoscopic contrast enhanced harmonic US techniques consistently revealed diffuse and focal types of AIP to have features consistent with vascularized lesions. Differentiation from the typically hypovascularized pancreatic adenocarcinoma was possible with CE (-E) US evaluation.

Transpapillary biliary stenting is a risk factor for pancreatic stones in patients with autoimmune pancreatitis

BACKGROUND AND STUDY AIM

Pancreatic stones occasionally develop in autoimmune pancreatitis (AIP), often worsen endocrine and exocrine functions, and occasionally cause pain attacks. However, the risks of pancreatic stones in AIP have been poorly studied. The aim of this study was to analyze the risk factors associated with pancreatic stone formation in cases of AIP.

PATIENTS AND METHODS

In total, 50 patients with AIP (39 males, 11 females; mean age 64.0 years), followed up for at least a year, were analyzed for their demographic and clinical findings and pancreatic stone occurrence.

RESULTS

In total, 50 patients were followed up for an average of 59.7 (12 - 120) months, with steroid treatment in 44 patients (88 %); pancreatic stones occurred in 14 (28 %) patients after the diagnosis of AIP and endoscopic treatment was needed in one patient with pain attack. The pancreatic stones appeared only in patients with long follow-up period (P < 0.001, 83.9 months vs. 49.6 months), biliary stenting (odds ratio [OR]: 8.40, P = 0.010), relapse (OR: 6.20, P = 0.023), jaundice (OR: 5.40, P = 0.019), and swelling of the duodenal major papilla (OR: 4.67, P = 0.040). Biliary stenting was placed for an average of 9.9 months in 27 patients. Multivariate analysis revealed a significant association only with biliary stenting (P = 0.011). The stones appeared relatively earlier in patients with stones in the main pancreatic duct or Santorini duct (22.1 months) than in patients where pancreatic stones developed elsewhere (53.4 months) (P = 0.018).

CONCLUSIONS

The risk of pancreatic stone development should be taken into account when a biliary stent is placed in patients with AIP.

Pancreatic cystic lesions with atypical steroid response should be carefully managed in cases of autoimmune pancreatitis

BACKGROUND AND AIM

Pancreatic cysts have been reported in cases with autoimmune pancreatitis (AIP) and are often treated by corticosteroid; however, their response to steroid has not been determined fully. We aimed to see the incidence and steroid response of pancreatic cysts and the features of cysts without proper response in cases with AIP.

METHODS

Fifty-eight AIP cases were analyzed for the incidence and associated factors of pancreatic cystic lesions (≥ 10 mm). Of these, 47 cases, determined for steroid response, were retrospectively investigated for the factors associated with cyst change by corticosteroid therapy.

RESULTS

At initial diagnosis, 17 pancreatic cystic lesions were recognized in 13 cases (22.4%) of AIP, with an average size of 30 mm (range: 11-130 mm), associated with higher incidence of elevated serum amylase (38.5% vs 11.1%, P = 0.02). Of these 13 cases, nine cases with 10 cystic lesions underwent steroid therapy in our hospital. All of seven unilocular cysts were dramatically shrunken or vanished in a few months; meanwhile, three cases with multilocular cysts showed scarcely any steroid response (P = 0.008). Of these three cases, two cases were revealed to accompany pancreatic ductal carcinoma, in contrast to null of seven unilocular cysts (P = 0.07).

CONCLUSIONS

Pancreatic cystic lesions are sometimes recognized in cases with AIP, and most unilocular cysts can be minimized by corticosteroids. However, clinicians must be alert for atypical pancreatic cysts, such as multilocular cysts or cysts without obvious steroid response.

Colovesical fistula caused by glucocorticoid therapy for IgG4-related intrapelvic mass

IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory disorder that can occur in almost all systemic organs and generally responds to corticosteroid treatment. We report a rare case of an IgG4-related intrapelvic mass lesion that responded to steroid therapy but caused a fistula between the sigmoid colon and bladder. A 71-year-old man was followed after treatment for hepatocellular carcinoma. Follow-up computed tomography (CT) incidentally depicted left hydronephrosis with an ill-demarcated intrapelvic mass lesion. This lesion was histologically diagnosed as IgG4-RD by open biopsy, and peroral steroid therapy was initiated. One month after starting steroids, a colovesical fistula was detected by follow-up CT. A colostomy and urethral catheterization were emergently performed. The patient recovered and the mass lesion was drastically minimized by the initiation of glucocorticoids; however, he still needs urethral catheterization. IgG4-RD develops in various systemic organs and generally responds well to steroids. Clinicians must be watchful for the complications of responses to corticosteroids, such as fistulization, when the mass lesion of IgG4-RD is adjacent to multiple luminal organs.

Diagnosis of autoimmune pancreatitis

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

Autoimmune pancreatitis with colonic stenosis: an unusual complication and atypical pancreatographic finding

BACKGROUND

Type 1 autoimmune pancreatitis (AIP) often accompanies various systematic disorders such as sclerosing cholangitis, sialoadenitis, retroperitoneal fibrosis, interstitial pneumonitis and nephritis. Although rarely reported in acute pancreatitis, colonic stenosis is an uncommon complication in cases with AIP.

CASE PRESENTATION

A 69-year-old Japanese man complained of abdominal pain and continuous diarrhea, resistant to intake of antimuscarinic and probiotic agents. A colonoscopy demonstrated a stenosis at the splenic flexure. Computed tomography revealed a focal enlargement of the pancreatic tail with a capsule-like rim, contacting with the descending colon. Endoscopic retrograde pancreatography (ERP) was unable to visualize the main pancreatic duct (MPD) at the pancreatic tail, despite a full contrast injection. A high serum IgG4 level (1060 mg/dL) and exclusion of pancreatic cancer by endoscopic ultrasound guided-fine needle aspiration suggested AIP, but did not fulfill the diagnostic criteria, and steroid therapy was initiated. One month after starting steroid intake, pancreatic swelling was minimized and the MPD was visualized by ERP, fulfilling the international consensus diagnostic criteria (ICDC) of AIP. Colonic stenosis was relieved and the patient's symptoms disappeared.

CONCLUSION

The present case is the first report of AIP developing colonic stenosis by the inflammatory infiltration. In this case, steroid therapy was effective for the diagnosis and treatment of pancreatic mass involving the descending colon.

Current status of research on autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis characterized clinically by frequent presentation with obstructive jaundice, histologically by lymphoplasmacytic infiltration with fibrosis, and therapeutically by a dramatic response to steroids. AIP have recently been classified into two subtypes, lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct centric pancreatitis (IDCP). The pathogenesis of AIP may involve genetic susceptibility, autoantibodies, molecular mimicry, imbalance of T-cell-mediated immune regulation, and gene mutation. In this article, we will systematically review typical and atypical clinical, imaging and histopathological features of AIP, with an emphasis placed on the advances in the diagnosis and treatment of this disease.