European Journal of Radiology 81 (2012) 807–810 Contents lists available at ScienceDirect European Journal of Radiology jo ur n al hom epage: www.elsevier.com/locate/ejrad Renal involvement in patients with autoimmune pancreatitis: Ultrasound findings Kewalee Sasiwimonphan a,1 , Brian Gorman a , Akira Kawashima a , Suresh T. Chari b , Naoki Takahashi a,* a Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA b Division of Gastroenterology, Department of Internal Medicine, Mayo Clinic, USA a r t i c l e i n f o Article history: Received 10 December 2010 Accepted 2 February 2011 Keywords: Pancreatitis Kidney Nephritis Ultrasound IgG4 Autoimmune a b s t r a c t Objective: The purpose of our study was to retrospectively evaluate the ultrasound findings of renal involvement in patients with autoimmune pancreatitis. Methods: 15 patients with autoimmune pancreatitis (15 male, 0 female, mean age 66 years old, range 44–85) who had renal involvement documented on CT or MR and had abdominal ultrasound within 1 month were included. Ultrasound images were retrospectively reviewed for presence or absence of renal involvement. Shape and echogenicity of the renal lesions were recorded. Results: In 8 out of 15 patients, at least one renal lesion was identified on ultrasound with a total of 9 kidneys. In 7 kidneys, lesions appeared as ill-defined, non-mass like areas of decreased echogenicity. Three lesions showed associated irregular lobular thickening of the renal parenchyma with bulging con- tour and 1 showed focal area of parenchymal loss. In 2 kidneys, the lesions were seen as solitary or multiple hypoechoic mass-like areas. Ill-defined, non-mass like lesions on ultrasound corresponded to well-circumscribed wedge-shaped lesions in all but one case on CT or MR. Mass-like lesions on ultrasound corresponded to well-circumscribed round lesions on CT or MR. Conclusion: Most common ultrasound findings of renal involvement in patients with autoimmune pan- creatitis were ill-defined area of decreased echogenicity. © 2011 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Autoimmune pancreatitis (AIP) is a rare type of pancreatitis caused by an autoimmune process [1]. AIP represents approxi- mately 7% of chronic pancreatitis [2] and 2–6% of patients who undergo pancreatic resection because of suspected pancreatic cancer [3,4]. Pathologically, AIP is characterized by infiltration of abundant IgG4-positive lymphoplasmacytic cells and fibrosis of the pancreas [5]. Characteristic imaging findings are diffuse enlargement of the pancreas with irregular narrowing of the main pancreatic duct [6,7]. Elevation of serum IgG4 is often present [8]. AIP is a systemic disease and extra-pancreatic involvement is common. Common organs involved beside the pancreas are biliary duct system (68–88%) [5,9,10] causing biliary strictures, salivary gland (12–48%) [5,9] and retroperitoneum (3–20%) [9,11]. * Corresponding author. Tel.: +1 507 284 3908; fax: +1 507 266 4735. E-mail addresses: kewalees@hotmail.com (K. Sasiwimonphan), gorman.brian@mayo.edu (B. Gorman), kawashima.akira@mayo.edu (A. Kawashima), chari.suresh@mayo.edu (S.T. Chari), takahashi.naoki@mayo.edu (N. Takahashi). 1 Current address: Department of Radiology, King Chulalongkorn Memorial Hos- pital, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand. Renal involvement is present in 14–39% of patients with AIP by CT or MRI [9,12–14]. Renal involvement is often multiple and bilat- eral, predominantly involving renal cortex. Involvement of renal sinus or perirenal fat has been described [12]. Pathologically, renal involvement is characterized by tubulointerstitial nephritis with dense infiltration by IgG4-positive lymphoplasmacytes [15,16]. In a study of eight patients with AIP and renal lesions doc- umented by CT, none of the renal lesions were detectable on ultrasound [13]. Thus, the purpose of our study was to retrospec- tively evaluate the ultrasound findings of renal involvement in AIP. 2. Materials and methods 2.1. Patients The retrospective case study was approved by our institutional review board. All patients had previously consented to the use of their medical records for purpose of research. This study was Health Insurance Portability and Accountability Act compliant. Through a maintained database we identified 163 patients with AIP. Of these, 15 patients (15 male, 0 female, mean age 66 years old, range 44–85) were included in the study who had renal involvement documented on contrast-enhanced CT or MR and had abdominal ultrasound within a 1 month period from CT or MR. Renal lesions were 0720-048X/$ – see front matter © 2011 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2011.02.002