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. Renal artery stenosis can also be classified by hemodynamic function. Shown below there is a table rewarding hemodynamic function.^[1]

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

Life Threatening Causes

Renal artery stenosis is caused by a heterogenous group of entities, that if left unattended may lead to ischemic nephropathy and consecuently death due to end stage renal disease.

Atherosclerosis
Fibromuscular dysplasia
Neurofibromatosis
Vasculitis
Congenital bands
Radiation

Common Causes

Atherosclerosis
Fibromuscular dysplasia

Managment of RAS

Clinical Clues to the Diagnosis of RAS

❑ Determine if one or more of the following is present:

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

❑If one of the above are present, proceed with Non- invasive imaging

❑If there are no clinical clues, proceed with invasive renal arteriography

Is patient allergic to contrast

Invasive Imaging

If yes proceed with US

If no check for:

❑ Implanted devices:

Pacemakers
Defibrillators
Cochlear implants
Spinal cord stimulators

❑ Claustrophobic patient

❑ Abdominal aortography to assess the renal arteries during coronary and peripheralangiography

If none of the above proceed with MRA

If yes to any of the above, proceed with CT

Negative noninvasive test but with high clinical suspicion

Evidence of RAS

Go to invasive imaging

Evidence of RAS

Confirmed RAS:

❑Proceed to medical therapy

❑Consider revascularization

Algorithm based on the 2013 AHA Guidelines Recommendations for Management of Patients with PAD.^[1]

Treatment

Medical/Pharmacological Therapy

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

Also, statins, optimal glycemic control, and smoking cessation are of supreme importance.

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 (>7cm)	Class IIb; LOE C
7. RAS and CRI with unilateral RAS (2 kidneys present)	Class IIb; LOE C

Shown below there is an algorithm of therapeutic options to consider 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