Renal artery stenosis resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Karol Gema Hernandez, M.D. [2]

Definition

Renal artery stenosis is defined as a dimished diameter of the lumen of the renal artery. There are different degrees of stenosis. Shown below there is a table that depicts the degree of stenosis according to the percentage of the lumen occluded.

Severity	Luminal Narrowing
Normal	0%
Mild	1-49%
Moderate	50-69%
Severe	70-99%
Occluded	100%

Renal artery stenosis can also be classified by hemodynamic function. Shown below there is a table rewarding hemodynamic function.

Hemodynamically significant RAS

≥70% by visual estimation

≥70% by intravascular ultrasound measurement

50-70% RAS with a systolic gradient of ≥20 mm Hg or a mean gradient of ≥10 mm Hg.

Causes

The primary goal of treating renal artery stenosis, either medically or by revascularization (surgical or percutaneous), is to prevent ischemic nephrophathy, and ultimately to diminish the presentation of clinical end points that may lead to all cause mortality.

Clinical Clues to the Diagnosis of RAS

❑ Determine if one or more of the above is present

Scenario Level of evidence 1.Onset of hypertension before the age of 30 years or severe hypertension after the age of 55 Class I; LOE B 2. Accelerated, resistant, or malignant hypertension Class I; LOE C 3. Development of new azotemia or worsening renal function after administration of an ACE inhibitor or ARB agent Class I; LOE B 4. Unexplained atrophic kidney or size discrepancy between kidneys of greater than 1.5 cm Class I; LOE B 5. Sudden, unexplained pulmonary edema Class I; LOE B 6. Unexplained renal dysfunction, including individuals starting renal replacement therapy Class IIa; LOE B 7. Multi-vessel CAD Class IIb; LOE B 8. Unexplained CHF Class IIb; LOE C 9. Refractory angina Class IIb; LOE C

❑If one or more of the above are present, proceed to further diagnostic testing

Noninvasive Imaging

Invasive Imaging

❑ Duplex ultrasound ❑ Gadolinium enhanced MRA ❑ CT angiography

❑ Abdominal aortography to assess the renal arteries during coronary and peripheral angiography

Negative noninvasive test but with high clinical suspicion

Evidence of RAS

Evidence of RAS

Renal angiography

Evidence of RAS

Confirmed RAS, proceed to treatment

Algorithm based on the 2013 AHA Guidelines Recommendations for Management of Patients with PAD.

Treatment

Treatment can be medical therapy alone or medical therapy plus angioplasty/stenting. However, recent studies reveal that although there are high technical success rates with angioplasty/stenting, the clinical end points are inconsistently and modestly modified. Therefore, raising the suspicion that PRI (percutaneous renal interventions) can incur in substantial costs without a significant public health advantage. The present algorithms are based in the most updated guidelines of the 2013 AHA Guidelines Recommendations for Management of Patients with PAD.

Pharmacological Therapy

The 4 main components of the BMT (best medical therapy) are:

• [[ACE inhibitors]
• ARB's
• Calcium channel blockers
• Beta blockers

Shown below there is a table depicting each medication dosage and its respective level of evidence (LOE).

Indications for Renal Revascularization

Indication	Level of Evidence
1.Hemodynamically significant RAS (see table above) with recurrent, unexplained CHF or sudden, unexplained pulmonary edema	Class I; LOE B
2. RAS with: Accelerated, resistant, or malignant hypertension Hypertension with unilateral small kidney Hypertension with medication intolerance	Class IIa; LOE B
3.RAS and CRI with bilateral RAS or RAS to solitary functioning kidney	Class IIa; LOE B
4. RAS and unstable angina	Class IIa; LOE B
5. Asymptomatic bilateral or solitary viableʰ kidney with a hemodynamically significant RAS	Class IIb; LOE C
6. Asymptomatic unilateral hemodynamically significant RAS in a viable* kidney	Class IIb; LOE C
7. RAS and CRI with unilateral RAS (2 kidneys present)	Class IIb; LOE C

ʰViable means kidney linear length greater than 7 cm.

Shown below there is an algorithm of therapeutic options after any of the indications for revascularization are met.

❑ Presence of one or more indications for revascularization:

❑Renal Angioplasty/Stent

❑ Renal artery surgery

Atherosclerotic RAS

Fibromuscular dysplasia RAS

Renal stent placement is indicated for ostial atherosclerotic RAS lesions that meet the clinical criteria for intervention

Balloon angioplasty with bailout stent placement if necessary is recommended for fibromuscular dysplasia lesions

Algorithm based on the 2013 AHA Guidelines Recommendations for Management of Patients with PAD.

References

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