To understand the characteristics and manifestations of IgG4-related disease (IgG4-RD) in abdomen and pelvis To familiarize key radiological findings of IgG4-RD with multimodality imaging correlation and its important disease mimics. To be aware of radiology’s crucial role in diagnosis, treatment response assessment and disease monitoring

IgG4-related disease (IgG4-RD) is an immune-mediated1 fibro-inflammatory condition1-3 that can involve multiple organ systems1-2. Diagnosis criteria are based on clinical, serological, radiological, histopathological features and response to corticosteroid therapy1-2, 4-7.Obscure clinical presentations, diverse spectrum of imaging manifestations, overlapping features with infectious and neoplastic conditions1-2, 6-8 frequently constitute diagnostic challenges and potential delay in diagnosis.High index of suspicion and awareness among radiologists is critical in achieving accurate and timely diagnosis, facilitating early initiation of immunosuppressive therapy1-2, 9, and therefore prevention of irreversible tissue fibrosis1, 3, 9...

To illustrate the spectrum of abdominal and pelvic manifestations of IgG4-RD, multimodality imaging features will be discussed, including ultrasound (USG), computed tomography (CT), magnetic resonance imaging (MRI) and 18F-FDG positron emission tomography (PET)-CT.Key diagnostic clues are highlighted to differentiate IgG4-RD from other malignant conditions through companion case comparison.Selected cases are also included to demonstrate post-treatment response, in terms of morphological, functional or metabolic assessment with 18F-FDG PET-CT.PANCREAS AND HEPATOBILIARY SYSTEMIgG4-related Autoimmune Pancreatitis (AIP) Manifests as Type 1 AIP1-2, 7. Not associated with Type 2 AIP1,...

Recognition of the characteristic imaging hallmarks and common occurrence of multi-organ involvement in IgG4-RD prompts early diagnostic investigations and timely initiation of medical treatment. 18F-FDG PET-CT is increasingly important in disease surveillance, treatment response assessment, and guiding target site selection for histological sampling. Image-guided biopsy enables histological diagnosis, assessment of post-treatment soft tissue residual disease activity, which is critical in subsequent treatment titration. Multidisciplinary collaboration with vital input from radiologists is conducive to overall patient management and well-being.

K. S. Ngai: Nothing to disclose S. C. Wong: Nothing to disclose C. Tang: Nothing to disclose H. M. Kwok: Nothing to disclose H. H-C. Lee: Nothing to disclose S. Y. Lam: Nothing to disclose F. H. Ng: Nothing to disclose N. Y. Pan: Nothing to disclose

Huynh KN, Kong MJ, Nguyen BD. Anatomic and Functional Imaging of Immunoglobulin G4-related Disease and Its Mimics. Radiographics. 2023 Mar;43(3):e220097. doi: 10.1148/rg.220097. PMID: 36821510. Martínez-de-Alegría A, Baleato-González S, García-Figueiras R, Bermúdez-Naveira A, Abdulkader-Nallib I, Díaz-Peromingo JA, Villalba-Martín C. IgG4-related Disease from Head to Toe. Radiographics. 2015 Nov-Dec;35(7):2007-25. doi: 10.1148/rg.357150066. Epub 2015 Oct 16. PMID: 26473450. Miyabe K, Zen Y, Cornell LD, Rajagopalan G, Chowdhary VR, Roberts LR, Chari ST. Gastrointestinal and Extra-Intestinal Manifestations of IgG4-Related Disease. Gastroenterology. 2018 Oct;155(4):990-1003.e1. doi: 10.1053/j.gastro.2018.06.082. Epub 2018 Sep 12....