Definition: Collection of urine in the renal pelvis that results in dilatation of the renal pelvis and calyces. It is caused by obstruction of urine flow, nephrolithiasis, or vesicoureteral reflux. Signs and symptoms include flank pain, nausea, vomiting, fever, and dysuria.
Synonyms (terms occurring on more labels are shown first): hydronephrosis
More information: PubMed search and possibly Wikipedia