Rare case of asymptomatic huge primary retroperitoneal pseudocyst reported

Retroperitoneal non-pancreatic or idiopathic pseudocysts are very rare lesions. The retro-peritoneum is a space situated behind the parietal peritoneum and in front of the transversalis fascia. The retroperitoneum consists of three parts: the anterior pararenal space, the perirenal space, and the posterior pararenal space. The anterior pararenal space contains pancreas, 2nd to 4th parts of the duodenum, and the ascending and descending colon. The perirenal space contains the kidneys, proximal ureters, adrenal glands, and perirenal fat. The posterior pararenal space contains fat tissue and join inferiorly to the pelvic extraperitoneal space.

Most of the retroperitoneal masses originate from the retroperitoneal organs and are not considered as the primary retroperitoneal masses. A primary retroperitoneal mass is diagnosed once the location is inside the retroperitoneal space and after exclusion of the originity from an organ. Primary retroperitoneal masses can be divided into solid and cystic groups and these two groups can be classified as neoplastic and non-neoplastic subgroups. Table 1 shows the differential diagnosis of the primary retroperitoneal masses