First of all, hydronephrosis is mainly due to the obstruction of the urinary system, which leads to the dilatation of the renal pelvis and calyces, thus retaining urine, collectively known as hydronephrosis. Generally speaking, hydronephrosis in women is categorized into physiological factors such as pregnancy or pathological factors such as primary and secondary. 1. Physiological factors: During pregnancy, especially in the middle and late stages of pregnancy, the uterus or the fetal head can compress the lower part of the ureter, causing hydronephrosis. In addition, excessive secretion of luteinizing hormone during pregnancy, luteinizing hormone can inhibit the peristalsis of the ureter, thus causing dilatation of the ureter and hydronephrosis. 2. Pathological factors (1) Primary: primary hydronephrosis is mainly due to the obstruction of the ureteropelvic junction. It is often due to the separation of muscle cells in the area by a large number of collagen fibers, which lose their normal arrangement and cannot effectively transmit the electrical activity of the pacemaker cells, preventing normal peristaltic transport, and in some cases, congenital hydronephrosis caused by mechanical obstruction. (2) Secondary: For secondary hydronephrosis, it is mostly caused by other diseases of the urinary system, such as obstructive lesions of the lower urinary tract (e.g. urethral stenosis, vesicoureteral reflux, etc.), tumors, polyps, stones, tuberculosis, inflammatory injuries, malformations, and renal prolapse. For women with bilateral hydronephrosis, they should go to regular hospitals in time and follow the doctor’s instructions for standardized treatment, so as not to delay the condition.