Lacunae: a urographic finding in chronic obstructive uropathy.

Lacunae, small spaces in the renal sinus that communicate with the caliceal fornices, have been mentioned rarely in the radiologic literature. These lesions have been reported to opacify during excretory urography in patients with current or previous urinary obstruction. Lacunae have been presumed to form in response to urine extravasation through the fornices, but there has never been gross anatomic or histologic proof of their existence. In two patients with obstructive uropathy, urographic-pathologic correlation confirmed the existence and nature of lacunae. On excretory urography, the appearance is likely to be confused with papillary necrosis.