Patient had a history of acute pancreatitis 10 years before. No underlying cause was found at the time (no history of alcohol abuse, no gallstones found on ultrasound).

In this case, IgG4-related disease is the primary concern considering both the retroperitoneal mass and the bilateral renal lesions. The fact that the renal lesions demonstrate restricted diffusion is also a typical feature of IgG4's deposits.

IgG4 levels were high on laboratory tests.

The differential diagnosis of the retroperitoneal mass would be idiopathic retroperitoneal fibrosis, lymphoma and malignant retroperitoneal fibrosis, with a differential diagnosis of pyelonephritis or metastases for the renal lesions.

Probably we can consider that the first episode of pancreatitis was also a manifestation of the IgG4-related sclerosing disease. The patient was treated with corticosteroid therapy, resulting in a reduction in the volume of the retroperitoneal mass. During follow up he developed autoimmune pancreatitis and IgG4-related sclerosing cholangitis, and was treated consequently with significant improvement of the findings.