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MR angiography is probably the investigation of choice nowadays for suspected RAS. ACEI can cause worsening renal function and AKI in those with renal artery stenosis
- Potentially treatable cause of hypertension
- Suspect in older patients with atheroma
- Suspect in younger patients with hypertensions
- Fibromuscular dysplasia (20-40%): younger often female. Beaded appearance.
- Atherosclerosis: older patients. The lesion usually ostial within 1 cm of the proximal renal artery. Often have missing pulses, bruits and atheroma
Clues to diagnose RAS
Suspected renal artery stenosis if there is a greater than 25% reduction in eGFR within 3 months of starting (or increasing the dose of) a renin-angiotensin system antagonist, refractory hypertension, pulmonary oedema, and/or a renal artery bruit.
- Worsening renal function with ACEI
- Disparity on renal size on USS > 1.5 cm (Ischaemic nephropathy)
- Flash pulmonary oedema
- Neurofibromatosis I (also get phaeochromocytomas)
- Renal bruit
- Intermittent claudication suggesting coexisting atherosclerosis + hypertension
- Captopril enhanced radionuclide renal scan: shows reduced uptake on the affected side which may be exacerbated by Aspirin or captopril
- MR Angiography with gadolinium enhancement shows a string of beads in Fibromuscular dysplasia and focal narrowing with atherosclerosis
- Spiral CTA with contrast less expensive than MRA
- Duplex doppler scan can assist renal artery flow velocity
- Intra-arterial angiography: the gold standard – should be carried out by experienced radiologists with minimal contrast load.
Indications for interventions
- Stenosis> 75%
- Flash pulmonary oedema
- Resistant hypertension
- Affecting solitary kidney
- Treat Pulmonary oedema. Avoid ACEI/AT2 blockers. Use Furosemide, Nitrates. Also consider low-dose dopamine for its natriuretic effect if no response to initial therapy.
- Best Medical - Aspirin, statins, BP meds, Calcium channel blockers, Diuretics to optimise blood pressure and atheroma
- Transluminal Angioplasty +/- stents but risks appear higher in those with Fibromuscular dysplasia
- Surgical resection of a stenosed portion of the artery
- Nephrectomy may be required
- Blood pressure improves but rarely returns to normal after treatment for atherosclerotic RAS. A lot depends on patient selection as at post mortem studies some degree of RAS is often seen in those with atherosclerosis and hypertension but may not be causative.