Retroperitoneal cysts (RCs) are rare. They are composed of both epithelial and mesothelial tissues, and those without an epithelial lining in the wall are called pseudocysts. Most retroperitoneal pseudocysts are pancreatic in origin, and nonpancreatic pseudocysts are very rarely reported. In this article, we present a case with a huge retroperitoneal nonpancreatic pseudocyst and discuss the diagnosis, treatment, and outcomes of this rare condition.
