renovascular hypertension naif alqarni بسم الله الرحمن الرحيم

RENOVASCULAR

HYPERTENSION

NAIF ALQARNI

بسم الله الرحمن الرحيم

PHYSIOLOGY OF R.A.A.S

Angiotensinogen The source of all angiotensins. The liver is the primary site of

synthesis, which is not stored but secreted directly after production.

Several hormones stimulate angiotensinogen synthesis by the liver, including estrogens, glucocorticoids .Stress-full stimuli.

Feedback control through AII and renin.

Renin The kidney is the major site of

renin production.

mechanisms affect the secretionA–Macula Densa Mechanism

Reduction of salt delivery stimulates renin secretion and vice versaB–Baroreceptor Mechanism

Diminished cell stretch as a result of renal hypoperfusion ,hyperpolarizes the juxtaglomerular cells.

C–Neural Mechanism

β-adrenergic ; and Dopamine . D–Endocrine and Paracrine Mechanisms

Prostaglandin E2 and I2

E–Intracellular Mechanisms

Agents that increase cyclic AMP.

Angiotensin-Converting Enzyme

pulmonary endothelial ACE is presumed to be the major site of ACE.

Angiotensin II

Effect of Angiotensin II on

Glomerular Circulation. Tubular Effects. Medullary Effects. Vascular Effects. Adrenal Effects. Central Nervous Effect. Gonadal Effect.

Angiotensin II Receptor Subtypes Angiotensin receptor subtypes,

named AT1 and AT2. In the kidneys, AT1 receptors are

located predominantly in the glomeruli and tubulointerstitium, whereas AT2 receptors are located in the large cortical blood vessels.

PATHOLOGY AND NATURAL HISTORY OF RVH

Atherosclerosis Approximately 70% of all

renovascular lesions are caused by atherosclerosis.

Atherosclerotic stenosis usually occurs in the proximal 2 cm of the renal artery.

The lesion involves the intima of the artery and, in two thirds of the cases, arises as an eccentric plaque.

Atherosclerosis

Seen predominantly in males and usually in older age groups.

progressive arterial obstruction occurs in 42% to 53% of patients with atherosclerotic renal artery disease, often within the first 2 years of radiographic follow-up.

Atherosclerosis

The incidence of progression to complete renal artery occlusion in the most wide study has ranged from 9% to 16%, and this has occurred more often in arteries that initially showed high degrees of stenosis.

Atherosclerosis

Atherosclerotic renal artery disease progresses in many patients and that loss of functioning renal parenchyma is a common sequela of such progression.And artery obstruction can eventuate in end-stage renal disease (ESRD).

Fibrous dysplasia

Intimal Fibroplasia

Primary intimal fibroplasia occurs in children and in young adults and constitutes approximately 10% of the total number of fibrous lesions.

characterized by a circumferential accumulation of collagen inside the internal elastic lamina.

Fibrous dysplasia

Medial Fibroplasia

Medial fibroplasia is the most common of the fibrous lesions, constituting 75% to 80% of the total number. It tends to occur in women between the ages of 25 and 50 years and often involves both renal arteries.

Fibrous dysplasia

Perimedial FibroplasiaPerimedial fibroplasia occurs predominantly in young women between the ages of 15 and 30 years and has therefore been referred to, rather crudely, as girlie disease. It constitutes about 10% to 15% of the total number of fibrous lesions.

Fibrous dysplasia

Fibromuscular Hyperplasia Fibromuscular hyperplasia is an extremely rare disease, constituting only 2% to 3% of fibrous lesions, and tends to occur in children and young adults.

Miscellaneous: Renal artery aneurysms, middle aortic syndrome, periarterial fibrosis, and post-traumatic intimal or medial disease. Variable in location and obstruction; occurs in diverse clinical settings .

PATHOPHYSIOLOGY OF RVH

Two-Kidney, One-Clip Model

ischemia of the clipped kidney

RAAS is activated

generalized vasoconstriction and systemic

hypertension

Two-Kidney, One-Clip Model

contralateral kidney higher than normal perfusion pressure

suppression of renin secretion

excreting higher than normal levels of

sodium and water

One-Kidney, One-Clip Model

solitary ischemic kidney secretes renin

activating the RAAS and resulting in systemic hypertension

No contralateral kidney

No excretion of Na and water

Stages in the development of renovascular hypertension

Acute stage Transitional stage

Days to weeks ,in solitary kidney No contralateral kidney no dauiresis and natuiresis hyper vlemia AII and hypervolemia maintain renal perfusion decrease renin levelSo, in this case hypertension depend on volume expansion .

So,In patients with renovascular disease, particularly those with bilateral RAS or those with a stenotic renal artery to a single kidney, ACE inhibitors or AII antagonist may cause a deterioration of renal function and azotemia.

Stages in the development of renovascular hypertension

In nmormal contralateral kidneyvolume expansion is avoided renin levels remain highSo, HTN is due to RAAS.

Stages in the development of renovascular hypertensionChronic stage

If blood flow is restored during these first 2 stages and renal perfusion is reinstated, blood pressure soon returns to a normal level. If renal hypoperfusion persists and stage 3 is reached, restoration of renal blood flow may not normalize blood pressure, presumably because of secondary irreversible vascular or renal parenchymal disease.

ISCHEMIC NEPHROPATHY

This is a clinical syndrome that occurs through different pathophysiologic mechanisms, is distinct from RVH, and can occur in the absence of elevated blood pressure.IN is the result of chronic hypoperfusion of the total functioning renal mass.

Renal autoregulation fails to maintain the GFR when renal perfusion decreases below 70 to 80 mm Hg.

This occurs when the luminal diameter of the renal artery is stenosed by more than 70% of the original size.

At this point, the stenosis becomes hemodynamically significant, resulting in a gradual deterioration of the GFR with an accompanying rise in the serum creatinine level.

This injury is not simply cell death related to a lack of oxygen and

nutrients? because;

The oxygen demand of the kidney never exceeds the supply.

kidney needs only about 10% of its blood flow to maintain its oxygen requirement.

So, the cellular mechanisms by which a decrease in renal size and IN develop are not well understood.

mechanisms play a role, including vascular mediators (endothelin, thromboxane, prostacyclin, and nitric oxide), calcium accumulation in or ATP depletion of the ischemic cells, production of oxygen free radicals, or disruption of cellular membrane polarity ( Textor, 1994 ).

ISCHEMIC NEPHROPATHY HISTOPATHOLOGY Tubular necrosis and atrophy. Glomeruli decrease in size with

wrinkling of the glomerular tuft and thickening of Bowman's capsule.

Localized or global glomerular sclerosis .

Hypercellularity of the juxtaglomerular apparatus is commonly seen.

CLINICAL FEATURES OF RENOVASCULAR HYPERTENSION

Clinical Clues The onset of hypertension. A family history. Sudden onset and shorter

duration. Hypertension that is difficult to

control Malignant hypertension or

hypertensive crises. Smoking.

Peripheral Plasma Renin Activity

To diagnose overactivity of the RAAS.

Antihypertensive medications should be discontinued for 2 weeks.

Blood should be collected 4 hours after the patient's ambulation.

Peripheral Plasma Renin Activity

Sensitivity of 80% Specificity 84%. 16% of patients with essential

hypertension have elevated PRA, whereas up to 20% of patients with RVH have normal PRA.

No anatomic information and has no value for diagnosing IN

Captopril Test Measurement of peripheral PRA before and

after an oral dose of captopril. All diuretics and ACE inhibitors need to be

discontinued for at least 1 week before the test.

A normal- or high-salt diet is needed Blood should be drawn with the patient in

the same position before and after captopril administration.

An oral dose of 25 mg of captopril is used, and blood is drawn again 1 hour after the dose.

Captopril Test

Positive when; postcaptopril PRA greater than 12

ng/mL/hr an absolute increase in PRA greater than

10 ng/mL/hr, 400% increase in baseline PRA (150%

increase if the baseline PRA was more than 3 ng/mL/hr).

sensitivity 74%. specificity is around 89% .

Renal Vein Renins

Subtracting the renin value in the arterial blood to the kidney (inflow) from the renin value in the venous blood from the kidney (outflow).

Hypersecretion of renin from the ischemic kidney (>50% of PRA) confirms the diagnosis of RVH.

Contralateral suppression of renin secretion (i.e. renal vein - IVC renin = 0) indicates an appropriate response of the normal contralateral kidney to the elevated blood pressure and predicts a cure of hypertension after revascularization.

Increasing severity of stenosis reduces blood flow to the ischemic kidney, resulting in an increased RVR increment

Captopril Renography

Oral captopril (25 to 50 mg) is usually used, although IV enalapril (0.04 mg/kg)

MAG3 befor and after one hour ACE inhibitor

asymmetry of renal size and functionspecific captopril-induced changes in the renogram normally less than 0.3, a 0.15 change is considered significant sensitivity 90% to 93%, specificity 93%

to 98%

Duplex Ultrasonography

Normal renal PSV averages 100 ± 25 cm/sec

The ratio of the renal PSV to the aortic PSV (renal PSV/aortic PSV) is called the renal aortic ratio (RAR). A ratio of 3.5 or more indicates severe (>60%) stenosis

sensitivity 89.5%. specificity 90.7%.

Magnetic Resonance Angiography

Only the proximal parts of the main renal arteries are visualized without the ability to image the distal arterial tree.

Computed Tomography Angiography

Spiral CTA lacks the ability to define disease distal to the main stem renal artery, and a relatively large volume of IV iodinated contrast material is required to perform the study.

Contrast Arteriography Gold standard for diagnosing renal

artery disease. Combined diagnostic and

therapeutic procedure. Carbon dioxide has been

introduced as a contrast agent for intra-arterial injection in an effort to reduce contrast nephrotoxicity from iodinated contrast material.

Angiography in primary intimal fibroplasia reveals a smooth, fairly focal stenosis, usually involving the proximal or midportion of the vessel or its branches.

Angiographically, medial fibroplasia demonstrates a typical “string of beads” appearance involving the distal two thirds of the main renal artery and branches.

SELECTION OF PATIENTS FOR SURGICAL OR ENDOVASCULAR THERAPY

atherosclerotic RVH Medical management Intervention with surgery or

endovascular therapy is best reserved for patients whose hypertension cannot be adequately controlled or when renal function is threatened by advanced vascular disease.

Fibrous dysplasia Because loss of renal function

from progressive obstruction is uncommon

in medial type, medical management is the best choice.

Intimal or perimedial fibroplasia generally progresses and often eventuates in ischemic renal atrophy so, early interventional therapy in these patients is therefore indicated.

Ischemic Nephropathy This designation applies to patients

with high-grade (>75%) arterial stenosis affecting their entire renal mass where such stenosis is present bilaterally or involves a solitary kidney.

The risk of complete renal arterial occlusion is significant, and if this occurs Intervention to restore normal renal arterial blood flow is indicated.

SURGICAL REVASCULARIZATION

Preoperative Preparation History, a physical examination, and an ECG, a thallium cardiac stress test is done on all operative candidates.

Operative Techniques Aortorenal bypass with a free

graft of autogenous hypogastric artery or saphenous vein remains a popular method in patients with a healthy abdominal aorta.

In older patients, severe atherosclerosis of the abdominal aorta splenorenal bypass for left renal revascularization and a hepatorenal bypass for right renal revascularization.

Operative Techniques

Use of the supraceliac or lower thoracic aorta for renal revascularization is a more recent surgical alternative in patients with significant atherosclerosis of the abdominal aorta and its major visceral branches.

Result

--Results of Surgical Revascularization for Atherosclerotic Renovascular Hypertension Series Patients (N) No. Cured No. Improved No. Failed

Van Bockel 105 19 (18%) 64 (61%) 22 (21%) Novick 180 55 (31%) 110 (61%) 15 (8%) Libertino 86 38 (44%) 44 (51%) 4 (5%) Hansen 152 22 (15%) 116 (75%) 14 (10%)

N.B Patients have been considered to be improved if they have either shown a reduction in diastolic pressure of 10 to 15 mm Hg or more or become normotensive with medication.

Patients with FD, 50% to 60% are cured, 30% to 40% are improved, and the failure rate is less than 10%.

PERCUTANEOUS TRANSLUMINAL ANGIOPLASTY

The original Gruntzig coaxial technique utilizes a No. 8 or 9 Fr renal guiding catheter through which a No. 4.3 or 4.5 Fr balloon catheter is passed over a guide wire traversing the stenotic segment through a femoral arterial puncture.

Complications

Transient deterioration of renal function

Intimal dissection Thrombosis of the renal artery

ResultsIn patients with F.D With the use of modern

equipment and increasing experience with the technique, technical success has been more than 90%.

In patients with A.S.O The cure rate is lower than that

for FD, commonly around 15%, and less in cases with bilateral PTA.

ENDOVASCULAR STENTINGIndications Poor immediate results during PTA. Restenosis after PTA. Stents are also used to treat

angioplasty complications and have markedly reduced the incidence of emergency surgery for these complications.

Primary stent placement is becoming increasingly popular in cases of RAS in which PTA alone is unlikely to be successful especially in ostial lesion.

Results

In B.P cure rates 31%. In renal function was achieved in 13% to

60%. Stabilization in renal function 24% to

Overall higher success of PTA with stenting in treating ostial ASO when compared with PTA alone and probably also justifies the increasing trend to perform primary stenting in these cases to avoid exposing patients to a secondary procedure ( Van de Ven et al, 1999 ).

OTHER RENAL ARTERY DISEASES

Renal Arterial Aneurysms

localized dilatation of the main renal artery or its branches or both caused by weakening of the elastic tissue and media of the arterial wall. Incidence ranges from 0.09% to 0.3.

Renal Arterial Aneurysms

Embolization of the aneurysm Placing an arterial stent in the

renal artery or the branch where the aneurysm originates,

Renal Arteriovenous Fistula

Renal arteriovenous fistulas are relatively uncommon lesions that are generally discovered during the course of angiographic evaluation for suspected renal or renovascular disease.Approximately 70% of fistulas occurring after needle biopsy of the kidney close

spontaneously within 18 months .

Renal Arteriovenous Fistula

Transcatheter angiographic occlusion.

Total or partial nephrectomy.

Renal Artery Thrombosis or Embolism

Causes of Renal Arterial Thrombosis; Blunt or penetrating trauma Aortic or renal artery angiography Atherosclerosis of aorta or renal

artery. Fibrous dysplasia of renal artery.

Renal Artery Thrombosis or Embolism

Causes of Renal Artery Embolism ; Bacterial endocarditis Aseptic cardiac valvular

vegetations Open heart surgery Atrial fibrillation Saccular renal artery aneurysm Cardiac tumor.

Middle Aortic Syndrome

The middle aortic syndrome is a rare disorder, occurring in children or young adults, characterized by nonspecific stenosing arteritis affecting the aorta and its major branches including the renal arteries.

This is thought to be a form of Takayasu's disease, and an autoimmune pathogenesis.

Renal autotransplantation is the surgical treatment of choice.

Page's Kidney

The clinical equivalent of this hypertensive model is the kidney compressed by a subcapsular or perirenal process causing renal ischemia, inducing unilateral hypersecretion of renin and contralateral suppression.Medical antihypertensive therapy and observation, percutaneous evacuation of the perirenal hematoma, open drainage of the hematoma, and nephrectomy have all

been used .

THANK YOU

renovascular hypertension naif alqarni بسم الله الرحمن الرحيم

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