Nutcracker syndrome, synonym: left renal veIn cntrapment syndrome, nutcracker phenomenon. It is a disease in which the left renal vein needs to pass through the angle formed by the abdominal aorta and superior mesenteric artery in the process of returning to the inferior vena cava, and is squeezed, causing hematuria, proteinuria, left lumbar and abdominal pain, and varicose veins of the spermatic cord. Diagnostic tests: In patients with non-glomerular hematuria, the possibility of this sign should be considered first except for other etiologies such as stones, hypercalcemia, masses, inflammation, etc. Ancillary tests: (1) Cystoscopy: Determine that the hematuria originates from the left ureteral opening. (2) Retrograde pyelogram: Injection of a small amount of contrast agent can immediately show that the contrast agent enters the tiny perinephric veins, suggesting the existence of a shunt between the pelvis and the first vein. (3) Selective left renal venography with simultaneous pressure measurement. Typically, an interruption of contrast filling is seen near the renal vein crossing the superior mesenteric artery. The pathological pressure variation in this condition ranges from 1.18 to 1.37 kPa (8.3 to 10.2 mmHg). (4) CT or MRI reveals dilatation of the distal end of the left renal vein, sudden thinning and angulation of the left renal vein between the abdominal aorta and superior mesenteric artery, and a small patchy concentration of contrast agent in the left renal sinus and inferior pole region, and ultrasound reveals dilatation of the distal end of the left renal vein, suggesting the nutcracker phenomenon. Treatment: For the treatment of this disease, as most patients with age, the increase of fat and connective tissue at the angle between the abdominal aorta and superior mesenteric artery or the establishment of collateral circulation, the stasis can be improved and the symptoms can be relieved, so clinical observation is generally taken for patients with short course, young age, mild symptoms and no complications. Some scholars believe that the treatment of silver nitrate solution via ureteral catheter to instill the renal pelvis is more effective. Surgical treatment is also a common treatment method. Indications for surgery include: ① after more than 2 years of observation or symptomatic medical treatment, the symptoms do not relieve or worsen, adult NCS patients can be treated more aggressively and can be observed for 6 to 12 months; ② those with complications, such as anemia, lumbar rib pain and varicocele, recurrent weakness, headache, anxiety, etc., which have affected work or life; ③ those with renal function impairment, excluding other causes. Interventional treatment, i.e. vascular stent placement at the left renal vein stenosis, has relatively good efficacy and has now increasingly replaced surgical treatment.