Hydronephrosis

Hydronephrosis — literally "water inside the kidney" — refers to distension and dilation of the renal pelvis and calyces, usually caused by obstruction of the free flow of urine from the kidney. Untreated, it leads to progressive atrophy of the kidney. One or both kidneys may be affected. In cases of hydroureteronephrosis, there is distention of both the ureter and the renal pelvis and calices.