What is kidney dilatation?

Hydronephrosis. Blockage of the ureter, the urinary passage out of the kidney, can lead to accumulation of fluid in the urinary space called hydronephrosis. This is also called renal dilation or dilatation. Blockage by urinary stones, tumors, valves, or strictures are common causes. Severe urine reflux from the bladder can cause this as well. Over time, unchecked dilatation can lead to decreased kidney function.