I. Causes of renal artery stenosis: 1, aortitis: the most common cause of domestic renal artery stenosis. The lesion involves the whole layer of the artery, and the middle membrane is the most serious; the renal artery lesion is mostly located in the opening part of the renal artery or the proximal section, which is centripetal confined narrowing, and can also be bead-like narrowing and expansion coexist, and the collateral circulation is more extensive. Mostly seen in young women, nearly 90% of cases in the age of 30 years. 2, atherosclerosis: the most common cause of foreign countries, accounting for the second in our country. It is common in elderly men, and the stenosis is mostly located at the opening of renal artery (within 2cm), which is more frequent and more involved bilaterally. 3, fibromuscular structural malformation: renal artery stenosis mainly occurs in the middle 1/3 – far 1/3 section, often extends to the branch. It is more common in young people, more female than male. It may mainly invade the inner, middle or outer membrane. Postoperative stenosis: mainly seen after renal transplantation, mostly caused by rejection. Second, the clinical manifestations of renal artery stenosis: 1, the age is generally less than 30 years old or more than 50 years old, and 78% of the people below 30 years old. 2, long-term hypertension suddenly exacerbated or sudden hypertension develops rapidly, presenting malignant hypertension symptoms. 3, Epigastric vascular murmur, 2/3 cases can be heard in the epigastric, renal area or back systolic murmur, high pitch, continuous. Third, auxiliary examination 1, color Doppler ultrasound. 2, Enhanced CT/CTA, MRA. 3, Renal artery stenosis imaging: the gold standard. Fourth, renal artery stenosis imaging performance: 1, renal artery stenosis or occlusion: aortitis and atherosclerosis caused by stenosis is mostly located in the root of the renal artery, from the opening of the renal artery and the proximity of the 1/3 section, and the stenosis caused by fibromuscular hyperplasia is located in the middle and distal segments, and can involve the branches. 2. Post-narrowing dilatation: it is common in severe limited stenosis, which is mostly pike-shaped dilatation. 3, aneurysm formation: can be shuttle or bead-shaped, bead-shaped for the typical manifestation of poor muscle fiber structure. Formation of collateral circulation: it usually starts from renal peripheral artery, lumbar artery, ureteral artery, etc. On the basis of the above, there is delayed and shallow renal parenchyma visualization and renal atrophy. However, it should be differentiated from renal atrophy caused by bilateral or unilateral chronic pyelonephritis, in which the renal arteries often show that except for the normal size of the renal artery openings, the renal artery trunks are generally atrophic and thin. Fifth, the treatment of renal artery stenosis: renal artery stenosis caused by this disease is traditionally based on surgical treatment, the main means of treatment for the affected nephrectomy, renal autotransplantation and extracorporeal renal vascular microscopic repair. Interventional therapy using renal artery balloon catheter expansion and/or renal artery stenting, with small trauma, safe and easy and good results and other advantages, is the treatment of renal vascular hypertension preferred method. Sixth, the indications for renal artery stenosis intervention: various causes, such as atherosclerosis, fibromuscular dysplasia, polyarteritis, etc. caused by renal artery stenosis and hypertension are preferred renal artery balloon dilatation angioplasty (PTA). Endovascular stenting is indicated for those who have poor results or recurrence of conventional PTA, those who have stenosis at the renal artery opening, and those who have endothelial injury after renal artery PTRA. For renal artery stenosis after renal transplantation, PTA is generally used, and endovascular stenting can be performed if necessary. Renal artery balloon dilatation angioplasty and stent implantation: 1. Transfemoral approach is generally used, which can accomplish most of PTA and renal artery stent implantation. When the renal artery is obviously traveling to the pedicle, a single hook catheter or Simons catheter can be used for insertion. When the balloon catheter is difficult to pass, the upper approach (axillary artery) can be used instead, which can make the technical success rate much higher. 2. Whether the catheter and guidewire, especially the balloon catheter and stent delivery system, can pass through the stenotic or occlusive segment is the key to the success of the technique. In addition to the choice of access mentioned above, it is very important to choose good equipment. Tapered head catheter, ultra-smooth guidewire, ultra-hard and ultra-long exchange guidewire should be necessary, and ultra-long metal sheath (40-50cm, 8F) or 8F guide catheter should be used for those who have obvious curvature of abdominal aorta. For renal artery occlusion, first use a suitable contrast catheter to insert to its proximal end, and then rotate the guidewire with a super-smooth guidewire to push it forward, and then follow up with a tapered-head catheter after “squeezing” the occluded segment. 3, the choice of balloon size, according to the angiographic film to measure the renal artery stenosis segment proximal diameter, to choose the diameter of the expansion balloon, the general balloon diameter should be equal to or slightly larger than 1mm. 4, for the renal artery stenosis of the beginning, due to the failure to correctly measure the diameter of the lumen, the use of 6mm balloon pre-expansion, according to the expansion of the arterial differential pressure changes and the status of the review of the imaging considerations of whether to switch to a larger balloon to continue to expand. The balloon catheter is sent into the catheterized artery. When sending the balloon catheter into the renal artery, the tip of the guidewire should be placed in the large branch of the renal artery and straightened, so that the segment of the guidewire located in the stenosis has sufficient support. 6. When it is necessary to place an internal stent, a stent with a diameter equal to or 1 mm larger than the corresponding renal artery diameter should be selected, and its length should be able to completely cover the stenotic segment and its two ends by 5 mm. For stenosis of the renal artery at the opening, the stent entering the abdominal aorta should be no more than 2 mm. 7. The positioning of the stent before release is very important. Marking method can be used, that is, according to the bone or body surface artificial marking to determine the site of stenosis, mainly used for stenting the proximal 1/3 of the renal artery to the far end of the stent placement, more convenient. The disadvantage of this method is that it can cause changes in the renal artery alignment after the ultra-stiff guidewire is delivered, and misplacement can occur when it is not done carefully. Another method of stent release positioning for the imaging method, that is, when the stent sent to a predetermined location, located in the opening part of the guide tube or long sheath or another pigtail catheter injected into the contrast medium, so that the abdominal aorta and renal artery visualization, and observation of stent proximal marking, to determine whether its position is correct. If necessary, it should be adjusted and re-imaged. This method has a higher localization accuracy than the former, and is especially suitable for stenting of stenosis in the open portion of the renal artery.