[Parapyelic cysts].

Parapyelic cysts present particular characteristics in relation to cystic disease of the kidney. Their intrasinusal development in contact with vascular and canalar elements of the renal hilum explains their often explosive symptomatology and the frequent need for surgical excision of the cyst--procedure difficult to accomplish and nearly always incomplete. Four cases are reported, including 2 with cysts communicating with excretory pathways, and symptoms, signs and diagnostic and therapeutic aspects discussed. Arguments are in favor of an acquired pathogenicity of these cysts (communication with excretory pathways, contingent presence of smooth muscle fibres in the cyst wall).