Pyelocalyceal diverticula are eventrations of the upper collector system in an intraparenchymatous location which communicate with the main collector system through a narrow channel. They have a thin wall and are lined with a transitional cells epithelium and surrounded by a muscle layer. Although these are non-secretory cavities they contain urine as a result of a passive filling from the adjacent collector system. The large majority of these lesions have less than 1 cm in diameter. Many are asymptomatic and are frequently found incidentally during elimination urography for other reasons. They rarely require treatment but may cause symptoms related to size or associated complications (infection or lithiasis). A number of years ago, definite treatment of complicated calyceal diverticulum was open surgery, but this has been defeated lately by less invasive techniques such as shock wave and percutaneous nephrolythotomy.