Increase in acute or chronic systemic values of the PA produced partial or complete occlusion of one or both renal arteries or their branches often correctable by surgery or percutaneous transluminal angioplasty.
Stenosis or occlusion of one or both main renal arteries or accessory renal artery or its branches may cause hypertension by stimulating the release of the enzyme renin by the juxtaglomerular cells of the kidney in question. The cross-sectional area of the lumen must be reduced by 70% before the stenosis is hemodynamically significant.
The most common cause of renal artery stenosis in patients> 50 years of age (usually men) is atherosclerosis, in younger patients (usually women), is one form of fibrous dysplasia. Rare causes of renal artery stenosis or obstruction are emboli, trauma, inadvertent ligation during surgery and extrinsic compression of the renal pedicle by a tumor.
Although renovascular disease represents the most frequent cause of curable hypertension (probably with the exception of female hormonal contraceptive therapy and excessive ingestion of ethanol), it explains <2% of all cases of hypertension.
Symptoms, signs and diagnosis
Renovascular hypertension should be suspected when diastolic hypertension appears in patients <30 or> 55 years of age or when a previously stable hypertension worsen suddenly. The rapid evolution towards malignant hypertension within 6 months suggests arterial impairment. A systolic-diastolic epigastric vascular murmur, usually sent to one or both upper abdomen and sometimes the spine, is a goal almost pathognomonic finding, but unfortunately is absent in about 50% of patients with forms of fibrous dysplasia and is detected rarely in patients with atherosclerotic renovascular basis.
Trauma to the spine or hips or acute pain in these regions, with or without hematuria should alert the doctor about the possibility of renovascular hypertension, medical history such data, however, occur only rarely. Renovascular hypertension is characterized by high GC and high peripheral resistance.
Renovascular hypertension and essential one are usually asymptomatic and only the history, the presence of a breath or epigastric vascular anomalies urography or scintigraphy with technetium-labeled acid pentetico 99 (99 Tc-DTPA) allow for the differential diagnosis. Is certainly worth running a diagnostic evaluation instrument for the full ability to detect surgically treatable lesions.
No diagnostic method available is ideal. All results are false-positive or false-negative, all are expensive and some dangerous. The most widely used test is scintigraphy with 99 Tc-DTPA, which has replaced the u and v in rapid sequence. A delay of perfusion or reduced function of kidney scintigraphy with 99 Tc-DTPA suggests the presence of ischemia. Its sensitivity and specificity can be improved by comparing images taken before and after oral administration of captopril.
Doppler ultrasound is a noninvasive reliable to determine the presence or absence of a significant stenosis (eg.,> 60%) at the level of main renal arteries. The sensitivity and specificity of this technique reach 90% in experienced hands. Unfortunately, the presence of a stenosis> 60% in one or both renal arteries in itself does not indicate that this is the cause of hypertension, but this observation coupled with the characteristic clinical picture is highly suggestive of renovascular hypertension. Measurements of renin activity in blood taken from the renal vein is often not necessary and are sometimes ground of error in diagnosis of renovascular hypertension.
Before planning an intervention (eg., Surgery, angioplasty), arteriography should be performed. The digital subtraction arteriography with Seldinger or by selective renal artery injection can confirm the diagnosis and can detect lesions smaller branches are not identifiable by ultrasound Doppler. The EV digital subtraction arteriography image is not as reliable as the Seldinger technique in identifying lesions orifice or secondary branches. Normal u and v in rapid sequence, a normal scan of 99 Tc-DTPA or the failure to demonstrate a significant stenosis by ultrasound Doppler arteriography do not exclude, if there are other indications that the motivation.
Prognosis and Treatment
Without treatment, the prognosis is similar to that primary hypertension. Most research has shown that an appropriate surgical hypertension resolved if the relationship between the two renal veins renin activity (involved side / healthy side) is> 1.5:1. However, many reports of patients with renal vein renin activity <1.5 recovered hypertension after revascularization or removal of the ischemic kidney. It was shown that the short duration of hypertension (<5 years) and features defect or u and v in rapid sequence scintigraphy, if taken together, provide, in predicting the outcome of surgery, the same reliability ratio renin activity of renal veins. To increase the reliability of the relationship of renin activity of renal veins, blood is drawn from the renal veins under conditions of sodium depletion, to stimulate renin release. This can be achieved by following a diet with 0.5 g of Na PO diuretics for 24 h, or by administering furosemide 40-80 mg IV, with blood sampling 30 min later. The bilateral lesions, which occur in 35% of cases, make the u and v in rapid sequence scintigraphy with 99 Tc-DTPA and the relationship of renin activity of renal veins less reliable. The renin activity of venous blood in the absence of stimulation, is often normal renovascular hypertension, but a sharp rise in renin activity 60 min after oral administration of 50 mg of captopril to 150% of baseline is suggestive of renovascular hypertension and may be used either as a screening test and as a prognostic test to decide about surgery. Captopril PO also causes excessive production of renin by the ischemic kidney and therefore improve the predictive power of activity rates renin renal vein.
Revascularization of the kidney affected by percutaneous transluminal angioplasty is recommended in young patients with fibrous dysplasia of the renal artery. Only when the percutaneous transluminal angioplasty is not technically feasible due to a widespread disease of the branches of renal arteries, is recommended to perform bypass surgery using a saphenous vein graft. Sometimes, a complete surgical revascularization require microvascular surgical techniques that can only be achieved ex vivo with the kidney transplant. The frequency of healing properly selected patients is 90% and surgical mortality is <1%. Medical therapy is always preferable to nephrectomy in young patients whose kidneys can not be revascularized for technical reasons.
Compared to the forms of fibrous dysplasia, the nature of atherosclerotic lesions respond less well to surgery and angioplasty, presumably because patients with atherosclerosis are older and more extensive vascular lesions within the kidney that is throughout the vascular system. Hypertension may persist after surgery and surgical complications are more common. Surgical mortality is higher in young patients with fibrous dysplasia of the renal artery. Restenosis within 2 years transluminal occurs up to 50% of patients with nefrovasocolare, especially when the plate is located at the ostium of the renal artery. The placement of a stent reduced the risk of restenosis. Because renovascular hypertension usually responds to drug therapy, medical treatment or for transcutaneous transluminal angioplasty with stenting is preferable to surgery in elderly patients with atherosclerotic lesions, unless it is clear that blood pressure can not be controlled or bilateral involvement or solitary lesion of the artery of the patient is not seriously endangering renal function. The decision to perform surgery must be based on the patient’s general status, age and previous response to medical therapy, and the location of the lesion and the risk involved for renal function. When possible, surgery should aim to repair and revascularization of the lesion rather than nephrectomy.