Causes of hydronephrosis:

Hydronephrosis is caused by congenital abnormalities of the urinary system or blood vessels, and secondary factors such as obstruction, resulting in dilatation of the renal pelvis and calyx and retention of urine.

When blood is filtered by the kidneys and forms urine, it collects in the renal pelvis and then flows to the bladder via the ureter. When the bladder slowly fills with urine, the pressure rises and the body needs to urinate. If the urinary tract is blocked, the kidney cannot drain urine, resulting in hydronephrosis. In addition, hydronephrosis can be caused by vesico-ureteral reflux. When the urinary tract structure is abnormal, urine may flow back to the kidneys via the ureter, making it difficult for the kidneys to empty. From the etiological point of view, it can be divided into congenital factors and secondary factors. Congenital factors include ureteral dysplasia, ureter-renal pelvis junction stenosis, abnormal blood vessel position, etc. Secondary factors include inflammation, stones, tuberculosis, tumor and other factors, as well as urinary tract external compression, such as abdominal, pelvic mass, retroperitoneal fibrosis, enlarged uterus, etc.