Splenic cysts are uncommon occurrences. They may be found incidentally or may be associated with left upper-quadrant pain, infection, hemorrhage, and unexplained splenomegaly. Splenic cysts are classified as “true” or “pseudo” cysts, in relation to the presence or absence of an epithelial lining. True cysts can be subdivided into paracytic and nonparacytic or “epithelial” cysts. In endemic regions, hydatid cystic disease caused by Echinococcus granulosus is the most frequent etiologic agent, with the spleen being the third most affected organ after the liver and lung. Epithelial cysts usually are considered to be congenital in nature and constitute approximately 25% of nonparacytic cysts in the United States. Pseudocysts are the most common type of cysts, accounting for 75% of nonparacytic splenic cysts in the United States. These pseudocysts of the spleen are thought to evolve as a consequence of splenic trauma. Malignancy within splenic cysts is an extremely rare event.

Large splenic cysts manifest clinically as progressively enlarging masses in the left upper quadrant, with approximately one-third being associated with pain or discomfort. Hemorrhage, secondary infection, and spontaneous rupture are infrequent complications but may be associated with repeat trauma. In neonates, spontaneous resolution of incidentally discovered splenic cysts has been reported.