Hydronephrosis may lead to renal insufficiency, but it does not belong to renal insufficiency, because the degree of hydronephrosis is relatively mild and does not have a significant impact on the function of the kidney at this time. Even if one kidney is completely lost, the other kidney can compensate for the metabolism of water and electrolytes and toxins, without the appearance of renal insufficiency. So the presence of hydronephrosis does not mean renal insufficiency, further examination and evaluation are needed, but prolonged hydronephrosis or severe hydronephrosis can eventually lead to renal insufficiency. Therefore, it is recommended that when hydronephrosis exists, we should go to the hospital for a timely examination to clarify the cause of hydronephrosis and then treat the problem. For example, if the hydronephrosis is caused by stones, it needs to be treated by lithotripsy, and if the hydronephrosis is caused by ureteral stenosis, it needs to be treated by dilation or surgery to drain the hydronephrosis in time, so that the pressure of the hydronephrosis on the kidney will disappear and the kidney function will not be further damaged.