Objectives

To highlight the spectrum of IgG4-related disease affecting organs of the abdomen and describe their imaging findings.

Background

IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory multisystemic condition. The involved organs share several pathologic features and clinical and serologic similarities, including a lymphoplasmacytic infiltrate enriched in IgG4-positive plasma cells, and a variable degree of fibrosis. Elevated serum concentrations of IgG4 are common. Abdominal manifestations usually include pancreatic, biliary, renal and retroperitoneal involvement though stomach, liver, prostate, lymph nodes and mesentery are rarely involved. Autoimmune pancreatitis [Type I] is the commonest manifestation of the disease.

Imaging findings OR Procedure findings

Patients often present with subacute development of a mass in or diffuse enlargement of the affected organ, sometimes mimicking a neoplastic process.

Imaging findings of IgG4 syndrome include focal or diffuse enlargement of the pancreas, smooth distal biliary strictures, focal renal involvement and rarely peripelvic infiltration, and/or abnormal periaortic or perirenal soft tissue.

Typically, the sites affected show late enhancement, restricted diffusion on MRI and uptake on PET/CT, with resolution (or near resolution) of findings following corticosteroid therapy.

The combination of imaging findings with serological-histological findings (increased IgG4 levels and positive biopsy) and eventually response to corticosteroid therapy confirm the diagnosis of the disease. Imaging with CT, MRI and / or PET-CT is essential for assessing both the extent of the disease and the response to treatment.

Conclusion

Radiologists should be familiar with its clinical and imaging manifestations to avoid a delay in diagnosis and unnecessary surgical interventions.