Horseshoe-shaped kidney is the most common fused kidney malformation, which can be completely asymptomatic, or it can present with symptoms such as pain in the lower back or umbilicus, lower abdominal mass, hydronephrosis, and stones. Due to the high opening of the ureter in the renal pelvis and the restriction of the renal pelvis by the fusion of the kidney, it cannot rotate normally and the ureter is displaced forward when it crosses the fused part, resulting in poor urine flow, etc., which makes hydronephrosis occur in 80% of cases and also easily leads to infection and stones. Common methods of examination: 1. On KUB plain films, shadows of the kidney and isthmus with abnormal axes are sometimes seen; 2. Intravenous pyelogram shows low position of the pelvic calyces on both sides, with the long axes parallel to each other or the upper pole tilted outward while the two lower poles of the kidney are close to the spine, so the extension lines of the lower pole of the kidney are opposite to the normal pelvis and cross in the caudal direction. Due to poor rotation, the renal pelvis and calyces overlap, and even the renal calyces point inward, the renal pelvis turns outward, and the upper ureter bends outward. Sometimes ureteral compression by blood vessels, fibrous band or isthmus can cause hydronephrosis. 3.CT examination can see that the lower poles of both kidneys are fused in front of the spine, and due to poor kidney rotation, the renal calyces are located in front of the kidneys, and the ureter crosses the isthmus on both sides of the anterior descending; 4.B ultrasound examination can find malformed horseshoe-shaped kidneys, which can clearly show that the lower poles of both kidneys are connected and cross the inferior vena cava and abdominal aorta in front.