HYPERTENSIVE RENAL DISEASE – SHOULD WE TREAT IT BY ENDOVASCULAR SURGERY?

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Introduction

Arterial hypertension in the adult population has been increasing and its estimated impairment is approximately 6%. The increased longevity of the population and the development of better studies and diagnostic methods corroborate this increase.

The etiology of hypertensive disease may be heart disease, parenchymal renal disease resulting from glomerular diseases and renal artery stenosis, in atherosclerotic disease or fibrodysplasia. These may result in a decrease of the parenchyma irrigation and also in the renal function, worsening the hypertensive conditions and the lost of function. Clinical drug therapy for arterial hypertension has been attempted for many years without effective results in a significant percentage of patients. Hence the need to study the pathophysiology of the disease and its impacts to choose the most appropriate therapy.

The hypertensive renal disease has two main etiologies: atherosclerotic disease with deposition of atheroma plaques in the wall of the renal arteries which often begins in the aorta and extends to the intra-renal renal artery and it is a degenerative disease; and the fibromuscular dysplasia that presents artery segments with stenosis and dilatation. It is also known that inflammatory diseases affect more young people, with higher incidence in women whereas degenerative diseases affect people over 50 years old.

Pathophysiology

The clinical picture is characterized by arterial hypertension resistant to medical treatment. When there is a decrease in renal perfusion there is an increase in renin which activates the renin-angiotensin systems I and II, and increases the production of aldosterone. The effect is the alteration in kidney filtration, increased plasmatic sodium and plasma volume. There is often an increased circulating renin in the blood.

Diagnosis

Clinical suspicion is done when blood pressure control is difficult, even with the use of several classes of drugs and in high doses. Laboratory tests used for the diagnosis are: urine I, blood chemistry to assess electrolytes and the clearence of creatinine. The clearance is the most reliable one because it compares the amount of creatinine in the urine (collected for 24 hours) and the blood thereby evaluating kidney function with a good premise for treatment. The use of imaging and flow examinations add subsides for diagnosis; therefore the echo-color Doppler must be done because it can give us the evaluation of the renal artery, the relation aorto renal and the parenchima resistance index.
When higher than three, it suggests renal stenosis with hemodynamic impacts and parenchyma impairment in the medium term.

Radioisotope examinations such as basal DTPA or with the use of captopril, as well as DMSA help diagnosis, but in our casuistry of 205 cases those examinations have shown interpreting errors that could lead to a wrong approach in the treatment of hypertensive renal disease. DTPA is an examination which compares the uptake and elimination of radiopharmaceuticals from the kidneys, so it is a comparative analysis between the two kidneys and one of them necessarily has to have normal function; DMSA, in turn, is in fact a flowchart that shows delay or not in renal perfusion.

The glomerular filtration rate (GFR) is a test currently considered a good marker of the function and predictive of successful treatment of renal ischemia.

Some authors find GFR a simple method and better than creatinine clearance and Cocroft-Gault Equation to decide for the best treatment.

Our professional experience indicates that the resistance index (RI) is more reliable for decision making. Selective arteriography is a method with good specificity and selectivity and we will discuss it below.

Endovascular treatment indication

Approximately 5% of the patients with hypertension have etiology in renal artery stenosis. The drug treatment is ineffective and it is observed that there is a progressive loss in renal function. It is often observed a renal asymmetry that may present capsular retraction and fibrosis. Surgical treatment of the renovascular hypertension is fully indicated when the hypertension is refractory to clinical treatment or when it is difficult to control it even if several classes of medication and high doses are used (three classes of antihypertensives and/or secondary complications to hypertension). Stenosis at or above 60%, serum creatinine above 1,5 mg/dl, glomerular filtration rate (GFR) of 30 ml/minute, creatinine clearance between 30 and 70 ml/min/1.73 m² and especially in a single kidney or transplanted.

Currently, the use of streaked laser to treat hypertension has been discussed but we consider that in the long term it may cause aneurysm of the artery by the destruction of the sympathetic innervation which determines the vascular tone.

Preoperative preparation must be careful with conducting blood biochemical tests, cardiac evaluation, arterial system with evaluation of pulses in the upper and lower limbs, segmental pressure measurements and calculation of the ankle brachial index. Smoking cessation and anticoagulation and antiplatelet aggregation four days before the procedure. In our service we prefer the approach via femoral artery provided there are no anatomical or pathological restrictions.

The procedure begins with selective arteriography of the renal arteries and stenosis correction at the same operative time. When the etiology is atherosclerotic we always implant a stent whose lesions are often ostial or in the proximal third of the renal artery. The monitoring of the patients for ten years showed that the stent placement retards the growth of the atherosclerotic plaque and hence the stenosis.

During the post-operative period we keep double antiplatelet aggregation for 60 days with acetylsalicylic acid and clopidogrel.

The protocol applied consists in: monitoring of patients is done on an outpatient basis with ultrasound at months 1, 3, 6, 12 and 24. The success of the intervention was 86.48%, 85.58%, 83.78%, 81.98% and 76% in intervals of: up to 6 months 6
Grounded in our clinical findings or when there is change in flow, with increase in velocity, we perform diagnostic angiography and angioplasty at the same operative time. The treatment of renovascular hypertension is effective when we treat the main branch of the renal artery; prevents the loss of organ function, decreases renal overload and prevents the patient from getting into a dialysis program.

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