The retroperitoneal fascial planes can be affected by various clinical disorders. Inmost of the cases retroperitoneal involvement occurs secondary to spread of a distinct underlying etiology. Hereinwe report two cases of primary retroperitoneal fasciitis diagnosed with imaging findings. The diagnosis of retroperitoneal fasciitis should be made by exclusion since various and more frequently encountered disorders including acute pancreatitis, duodenitis, pyelonephritis, and appendicitis may present with similar imaging findings. (C) 2017 Elsevier Inc. All rights reserved.