LEARNING OBJECTIVES: 
1. To illustrate imaging findings of IgG4-related sclerosing diseases affecting various abdominal organs including Liver, biliary tract, pancreas, retroperitoneum, kidneys, lymph nodes.
2. To inform the imaging features of IgG4-related diseases of abdomen which can be helpful to differentiate from many of tumorous or other inflammatory abdominal diseases.

BACKGROUND: CONCLUSION:
Immunoglobulin G4 (IgG4)–related disease is a recently proposed clinical-pathologic entity characterized by fibroinflammatory lesions rich in IgG4-positive plasma cells and, often but not always, elevated serum IgG4 concentrations.
Although definitive diagnosis requires histopathologic analysis, imaging plays an important role in detection and characterization of IgG4-related diseases involving abdominal organs. 
Because IgG4-related disease usually shows a marked response to corticosteroid therapy, radiologists should be familiar with its clinical and imaging manifestations to avoid a delay in diagnosis and unnecessary surgical interventions. 
The purpose of this exhibition is to review radiologic findings and mimics of IgG4-related diseases in abdomen. 

IMAGING FINDINGS AND PROCEDURE DETAIL:
In this exhibit, we’ll discuss the clinical manifestations and pathophysiology of various IgG4-related sclerosing diseases of abdomen.
We classified IgG4-related diseases into 7 groups according to the involved abdominal organs; Pancreas, liver, biliary tree, kidney, small bowel mesentery, retroperitoneum and lymph nodes.
Spectrums of imaging findings of of IgG4-related sclerosing diseases of abdomen will be reviewed and compared to their various mimickers
- Autoimmune pancreatitis vs. pancreatic cancer, pancreatitis
- Liver involvement vs. malignant hepatic tumor
- Biliary involvement vs. primary sclerosing cholangitis, cholangiocarcinoma
- Renal involvement vs. tumor, inflammation, infarct
- Retroperitoneal fibrosis vs. lymphoma
- Vascular involvement vs. other arteritis
- Lymphadenopathy vs. lymphoma or metastasis

CONCLUSION:
IgG4-related disease is a unique and distinct systemic disease that is frequently misdiagnosed as neoplastic and other inflammatory processes.
The recognition of the typical imaging patterns in each abdominal organ can raise the suspicion of the disease, and the combination of radiologic, serologic, and histologic findings can lead to correct diagnosis, ensuring effective treatment.

IgG4-related Sclerosing Diseases Involving Abdominal Organs; Radiologic Findings and Differential Diagnosis