Renovascular disease

Etiology & Pathophysiology
Causes of Ischemic Renal Disease
 * Atherosclerotic Renal Artery Stenosis (ARAS)
 * Atherosclerosis accounts for approximately 90% of the cases of RAS and is the predominant lesion detected in patients >50 years of age
 * The presence and number of diseased coronary arteries predicts the likelihood of ARAS
 * RAS resulting from atherosclerotic disease is common in (18% to 20%) individuals undergoing coronary angiography (1)
 * RAS resulting from atherosclerotic disease is even more common (35% to 50%) in individuals undergoing peripheral vascular angiography for occlusive disease of the aorta and legs (2)
 * Fibromuscular dysplasia
 * Unknown etiology
 * Second most common cause of RAS
 * Affects middle-aged women
 * More common in first-degree relatives and in the presence of the ACE-I allele.
 * Renal artery involvement is seen in 60% of cases - frequently bilateral compromise.
 * Progressive renal stenosis is seen in 37% of cases and loss of renal mass in 63%
 * Nephroangiosclerosis (HTN injury)
 * Diabetic Nephropathy (small vessels)
 * Renal thromboembolic disease
 * Atheroembolic renal disease
 * Aortorenal dissection
 * Post renal transplant RAS
 * Renal artery vasculitis
 * Trauma
 * Neurofibromatosis
 * Thromboangiitis obliterans
 * Scleroderma

Incidence

 * Prevalence of Renal Artery Stenosis
 * Most Common Cause of HTN
 * Incidence of Renal Artery Stenosis at Cardiac Catheterization

Diagnosis

 * Manifestations of Renovascular Disease (3)
 * Asymptomatic "Incidental RAS"
 * Renovascular Hypertension
 * Ischemic Nephropathy
 * Accelerated CV Disease
 * Congestive Heart Failure
 * Stroke
 * Secondary Aldosteronism

Clinical Clues to the Diagnosis of Renal Artery Stenosis-ACC/AHA Guidelines

 * CLASS I
 * Onset of hypertension before the age of 30 years or severe hypertension after age 55; level of evidence B
 * Accelerated, resistant, or malignant hypertension; level of evidence C
 * Development of new azotemia or worsening renal function after administration of an ACE inhibitor or ARB agent; level of evidence B
 * Uneaplained atrophic kidney or sizse discrepancy between kidnyes of >1.5cm; level of evidence B
 * Sudden, unexplained pulmonary edema; level of evidence B
 * CLASS IIa
 * Unexplained renal dysfunction, including individuals starting renal replacement therapy; level of evidence B
 * CLASS IIb
 * Multivessel coronary artery disease; level of evidence B
 * Unexplained congestive heart failure; level of evidence C
 * Refractory angina; level of evidence C

Diagnostic Methods to Detect Renal Artery Stenosis - ACC/AHA Guidelines

 * CLASS I
 * Duplex ultrasound sonography is recommended as a screening test to establish the diagnosis of renal artery stenosis; Level of eveidence: B
 * Computed tomographic angiography(in individuals with normal renal function) is recommended as a screnning test to establish the diagnosis of renal artery stenosis; Level of eveidence: B
 * Magnetic resonance angiography is recommended as a screening test to establish the diagnosis of renal artery stenosis; Level of eveidence: B
 * When the clinical index of suspicion is high and the results of noninvasive tests are inconclusive, cathether angiography is recommended as a diagnostic test to establish teh diagnosis of renal aretry stenosis; Level of eveidence: B
 * CLASS III
 * Captopril renal scintigraphy is not recommended as a screening test to establish the diagnosis of renal artery stenosis; Level of eveidence: C
 * Selective renal vein measurements are not recommended as a useful screening test to establish the diagnosis of RAS; Level of eveidence: B
 * The plasma renin activity is not recommended as a useful screening test to establish the diagnosis of RAS; Level of eveidence: B
 * The captopril test (measurements of plasma renin activity following captopril administration) is not recommended as a useful screening test to establish the diagnosis of renal artery stenosis; Level of eveidence: B

Indications for Revascularization

 * Reasons to Revascularize Atherosclerotic Renovascular Disease
 * Treat Symptoms
 * Prevent Future Illness
 * Lower BP
 * Preserve Renal Function
 * “Bystander” Effects
 * Prevent Death
 * Prevent MI
 * Prevent CHF
 * Prevent CVA
 * Indications for revascularization of RAS
 * hypertension
 * Failure of medical therapy despite full doses of 3 drugs, including diuretic
 * Compelling need for ACE inhibition/angiotensin blockade with angiotensin-dependent GFR
 * Progressive renal insufficiency with salvagable kidneys
 * Recent rise in serum creatinine
 * Loss of GFR during antihypertensive therapy (e.g., ACEI)
 * Evidence of preserved diastolic blood flow (low resistive index)
 * Circulatory congestion, recurrent “flash” pulmonary edema
 * Refractory congestive heart failure with bilateral renal artery stenosis

Renal Arteriography

 * Abdominal Aortogram: identification of ostia of the renal arteries and accessory renal arteries (25% of population)
 * Arteriography should include both the arterial phase and the nephrographic phase
 * Disease involving renal bifurcations require cranial or caudal angulation to open out the lesion
 * Evidence of aortic atheroma: technique of no-touch angiography is recommended

Brachial Approach

 * For renal arteries that are oriented cephalad.
 * When the aorta is occluded distally or the renal artery takeoff is severely angulated
 * Proximal renal artery segment initially courses inferiorly and posteriorly braquial approach allows more coaxial alignment.
 * Greater incidence of vascular site complications

Femoral approach

 * Renal artery angioplasty and stenting are usually performed via retrograde femoral approach.
 * When the real artery origin is oriented horizontally or caudally with respect to the aorta, femoral approach is preferred.

Complications of Percutaneous Renal Revascularization

 * Atheroembolism into the renal or peripheral vascular bed = cholesterol embolization
 * Dissection of renal artery or the wall of the aorta
 * Acute or delayed thrombosis
 * Infection
 * Rupture of renal artery
 * Renal perforation

Favorable Predictors
Successful Outcome For Control Of Hypertension Successful Salvage Or Preservation Of Renal Function
 * Rapid acceleration of hypertension over the prior weeks or months
 * Presence of “malignant” hypertension
 * Hypertension in association with flash pulmonary edema
 * Contemporaneous rise in serum creatinine
 * Development of azotemia in response to ACE inhibitors administered for control of hypertension.
 * Recent rapid rise in creatinine, unexplained by other factors
 * Azotemia resulting from ACE inhibitors
 * Absence of diabetes or other cause of intrinsic kidney disease
 * Presence of global renal ischemia, wherein the entire functioning renal mass is subtended by bilateral critically narrowed renal arteries or a vessel supplying a solitary kidney.

Unfavorable Predictors

 * Renal atrophy demonstrated by kidney length <7.5 cm on ultrasound
 * High renal resistance index detected by duplex ultrasound
 * Proteinuria > 1gm/day
 * Hyperuricemia
 * Creatinine clearance <40 mL/minute