It is a rare congenital malformation in urology, which is caused by the abnormal development of the vena cava during the embryonic period, resulting in a change in the position and course of the ureter, causing ureteral drainage or obstruction, resulting in hydronephrosis and ureteral dilatation and eventual loss of right kidney function. The disease is asymptomatic in the early stages and often appears at the age of 30-40 years. It is mainly caused by distension and pain in the lower back and abdomen due to obstruction of urine drainage after compression of the right ureter, and renal colic and hematuria can occur when combined with infection or secondary kidney stones, which can lead to loss of kidney function in severe cases. In the past, this disease was often difficult to diagnose before surgery, but in recent years, the accuracy of preoperative diagnosis has been greatly improved due to the continuous improvement of examination techniques. The posterior vena cava ureter can be divided into two types according to the x-ray performance: Type I (low loop type), which is commonly seen in IVU as a dilated right ureter, then curved toward the midline in an “S” shape, usually overlapping with the conus at the level of the 3rd and 4th lumbar vertebrae, and may be accompanied by varying degrees of hydronephrosis in the renal pelvis and upper middle ureter. In type II (high loop type), the posterior ureteral portion of the inferior vena cava and the renal pelvis are inverted L-shaped or sickle-shaped at almost the same level on IVU and RGU examination, and the kidney is normal or mildly hydrated. This type is rare and easily confused with malformations of the renal pelvis and ureteral junction. Surgical treatment is required to relieve the obstruction and correct the underlying anatomic deformity. Currently, most cases are treated by ureteral repositioning correction, i.e., the ureter is repositioned by cutting off the upper ureter, relocating it before the vena cava, relieving the compression, and then performing end-to-end ureteral anastomosis.