Renal involvement in patients with autoimmune pancreatitis: CT and MR imaging findings

Purpose: To retrospectively evaluate computed tomographic (CT) and magnetic resonance (MR) imaging renal findings at clinical presentation, during treatment, and at follow-up in patients with autoimmune pancreatitis (AIP). Materials and Methods: This HIPAA-compliant study received institutional review board approval. All patients included had previously consented to the use of their medical records for the purpose of research. Forty-five patients (38 male and seven female patients; mean age, 64 years) with diagnosis of AIP were included. Forty patients underwent CT or MR imaging at clinical presentation; 33 patients (including five without imaging at presentation) underwent follow-up, CT and MR images were reviewed in consensus by two radiologists for the presence of renal involvement. Various features were evaluated. Clinical characteristics at presentation were compared between patients with and patients without renal involvement. Results: Of the 40 patients who underwent imaging at presentation, 14 (35%) had renal involvement (12 with parenchymal involvement and five with extraparenchymal involvement). Renal parenchymal lesions showed decreased enhancement and appeared as small peripheral cortical nodules, round or wedge-shaped lesions, or diffuse patchy involvement. Thirteen patients with renal involvement at presentation underwent a follow-up study. Renal lesions in 10 patients regressed (in nine, after steroid treatment) but progressed in three patients without steroid treatment. Renal lesions were found in two other patients during follow-up. No significant difference in the clinical characteristics was found between patients with and patients without renal involvement. Conclusion: Renal involvement in patients with AIP is relatively common and predominantly involves the cortex, of the kidney. The lesions improve after steroid treatment but can progress without steroid treatment.