Nutcracker syndrome, also known as left renal vein compression syndrome, is characterized by proteinuria, mainly microalbuminuria, which is usually quantitatively tested and does not contain >1000 mg/day of protein in the urine. More patients with Nutcracker syndrome test for abnormalities in the urine, which may be dominated by hematuria. Nutcracker syndrome is a left renal vein in the body that is affected by the gap between the angle between the abdominal aorta and the superior mesenteric artery. When an adolescent is thin, the pinch may become smaller, and the smaller pinch may put pressure on the left renal vein, leaving the kidneys in a stagnant state, at which point urine testing may reveal abnormalities. Some patients may show hematuria, while others may show proteinuria. As the body gradually gains weight, the fat gap in the middle of the angle of entrapment fills up, the angle of entrapment gradually opens, and the pressure on the left side of the vein is gradually reduced.