Children with normal morning urine and abnormal urinalysis after exercise or in the afternoon is a frequently encountered problem in the pediatric nephrology area, and the left renal vein nutcracker phenomenon should be considered more often. Suggestions: 1. Do ultrasound to understand the left renal vein nutcracker phenomenon. 2, do upright test to clarify the effect of left renal vein nutcracker on the kidney. The method of upright test is as follows: 1, urine specimens are taken before and after the upright test; 2, urine needs to be urinated before going to bed, and urine specimens are taken in the morning (morning urine) for testing; 3, then immediately stand against the wall, with heels 15-20 cm from the wall, head against the wall, arching the waist (abdomen convexity) for 20 minutes, and then urinate and take specimens for testing when there is an urge to urinate (about 1 hour). The prognosis is that the nutcracker phenomenon in children is a temporary phenomenon in adolescence and has a good prognosis. As children grow older, effective collateral circulation is established, bruising is improved, and adipose tissue around the beginning of the superior mesenteric artery is increased, all of which relieves local pressure on the renal vein, and hematuria disappears without special treatment. However, since some triggers such as strenuous exercise and cold can trigger hematuria and proteinuria or cause recurrent attacks, the above-mentioned triggers should be avoided so that the child can pass through puberty smoothly.