Renal Artery Stenosis for NP
Renal Artery Stenosis for the Nurse Practitioner Licensing Exam
- Definition:
- Renal artery stenosis (RAS) is the narrowing of one or both renal arteries, leading to reduced renal blood flow, activation of the renin-angiotensin-aldosterone system (RAAS), and secondary hypertension.
- Etiology:
- Atherosclerosis:
- The most common cause of RAS, seen in older adults with cardiovascular risk factors such as hypertension, diabetes, and smoking. Plaques form in the proximal renal artery, reducing blood flow.
- Fibromuscular Dysplasia (FMD):
- A less common cause, typically seen in younger women. FMD is characterized by abnormal arterial wall growth, leading to stenosis and a “string of beads” appearance on angiography.
- Pathophysiology:
- Reduced blood flow to the kidney is perceived as low blood pressure, triggering RAAS activation. This results in systemic vasoconstriction, sodium retention, and elevated blood pressure. Prolonged ischemia from severe or bilateral RAS can lead to ischemic nephropathy and chronic kidney disease.
- Clinical Features:
- Resistant Hypertension:
- Hypertension unresponsive to ≥3 antihypertensive agents. It may present as sudden worsening of previously controlled blood pressure.
- Renal Dysfunction:
- An abrupt increase in serum creatinine after starting ACE inhibitors or ARBs may indicate bilateral RAS or RAS in a solitary kidney.
- Abdominal Bruit:
- A systolic-diastolic bruit may be auscultated over the epigastrium or flank.
- Flash Pulmonary Edema:
- Sudden pulmonary edema, often linked to volume overload, can occur in severe bilateral RAS.
- Diagnosis:
- Imaging:
- Duplex Ultrasound: Non-invasive screening test that detects increased blood flow velocity in stenosed arteries.
- CT Angiography (CTA) or Magnetic Resonance Angiography (MRA): Provide detailed images of the renal arteries.
- Renal Arteriography: The gold standard for diagnosing RAS.
- Management:
- Medical Therapy:
- ACE inhibitors or ARBs are used with caution in unilateral RAS. Statins and antiplatelet therapy are indicated for atherosclerotic disease.
- Revascularization:
- Angioplasty is indicated in cases with declining renal function, resistant hypertension, or recurrent pulmonary edema.
Key Points
- Renal artery stenosis is most commonly caused by atherosclerosis and fibromuscular dysplasia.
- Clinical features include resistant hypertension, renal dysfunction, and sometimes flash pulmonary edema.
- Diagnosis involves imaging techniques such as duplex ultrasound, CTA, MRA, or renal arteriography.
- Treatment includes antihypertensive medications and revascularization in severe or symptomatic cases.