Renal artery stenosis (RAS) is narrowing of the renal artery and is the most important cause of renovascular hypertension and ischemic nephropathy. Two main etiologies exist: atherosclerosis (90%, proximal 1/3 — ostium and proximal segment) and fibromuscular dysplasia (10%, distal 2/3 — young women). Hemodynamically significant stenosis is defined as >60% narrowing or >20 mmHg pressure gradient. CT/MR angiography and Doppler ultrasound are used for diagnosis.
Age Range
25-80
Peak Age
60
Gender
Equal
Prevalence
Uncommon
In atherosclerotic RAS, atheromatous plaque accumulates at the renal artery ostium or proximal segment, narrowing the lumen. This narrowing reduces blood flow to the kidney and triggers renin release from the juxtaglomerular apparatus (renin-angiotensin-aldosterone system activation) → hypertension develops. In advanced stenosis, kidney parenchyma undergoes ischemic atrophy and the kidney shrinks. On CT angiography, the lumen diameter is reduced at the stenosis site; proximal atherosclerotic plaque calcifications may be prominent. On Doppler US, tardus-parvus waveform (low resistive index, delayed systolic peak) forms distal to the stenosis because the stenosis reduces arterial pressure and flow velocity.
Delayed systolic peak and low-amplitude waveform in intrarenal arteries — indirect but reliable Doppler finding of proximal renal artery stenosis.
Focal or segmental narrowing of the renal artery lumen on CT angiography. Atherosclerotic stenosis involves the proximal 1/3 (including ostium) with accompanying calcified plaque. In FMD, string-of-beads pattern is seen in the distal 2/3.
Report Sentence
Hemodynamically significant stenosis is identified in the proximal right/left renal artery with approximately ___% luminal narrowing.
Tardus-parvus waveform in intrarenal segmental/interlobar arteries: delayed systolic peak (acceleration time >0.07 seconds), low resistive index (<0.5), and decreased systolic velocity. This indirect finding indicates proximal renal artery stenosis.
Report Sentence
Tardus-parvus waveform is identified in intrarenal arteries of the right/left kidney, supporting proximal renal artery stenosis.
Elevated peak systolic velocity (PSV >180-200 cm/s) in the main renal artery trunk and renal-aortic ratio (RAR) >3.5. These direct findings indicate renal artery stenosis.
Report Sentence
Peak systolic velocity of ___ cm/s is measured in the right/left main renal artery, consistent with hemodynamically significant stenosis (RAR: ___).
Luminal narrowing of the renal artery on gadolinium-enhanced MR angiography. MRA is not affected by atherosclerotic calcifications (advantage over CT). Phase-contrast MRA can provide quantitative flow assessment.
Report Sentence
Hemodynamically significant stenosis of the right/left renal artery is identified on MR angiography.
Decreased and delayed enhancement of the affected kidney on nephrographic phase. In severe stenosis, the kidney is shrunken with accompanying cortical thinning.
Report Sentence
Decreased and delayed enhancement of the affected kidney is identified, suggesting functional asymmetry consistent with renal artery stenosis.
Size difference >1.5 cm between the two kidneys. The kidney on the chronic stenosis side is shrunken with cortical thinning. This finding indicates chronic ischemic nephropathy.
Report Sentence
Size reduction and cortical thinning of the right/left kidney are identified, consistent with chronic ischemic nephropathy.
Criteria
Proximal 1/3 involvement (including ostium). Advanced age (>50), atherosclerosis risk factors.
Distinct Features
Calcified plaque, mural thrombus, aortic atherosclerosis accompanies. May be bilateral. Stenting or medical therapy. CORAL trial showed stenting is not superior to medical therapy.
Criteria
Distal 2/3 involvement. Young women (age 20-50). String-of-beads pattern.
Distinct Features
Calcification is generally absent. Angioplasty is effective in treatment. FMD should also be investigated in carotid arteries.
Criteria
Stenosis at the anastomosis site or proximal donor artery after kidney transplantation. Usually develops within the first 1-2 years.
Distinct Features
Presents with graft dysfunction and resistant hypertension. Doppler US is the screening tool. Angioplasty/stenting treatment.
Distinguishing Feature
FMD shows string-of-beads pattern in distal 2/3 without calcification. Atherosclerotic stenosis is proximal 1/3 + calcified plaque.
Distinguishing Feature
Takayasu arteritis shows long-segment concentric wall thickening and enhancement. Atherosclerotic stenosis has dominant focal plaque findings.
Distinguishing Feature
Renal artery aneurysm shows dilatation unlike stenosis. Stenosis is characterized by luminal narrowing, aneurysm by expansion.
Distinguishing Feature
PAN shows multiple small intrarenal artery microaneurysms. RAS has focal stenosis of the main renal artery.
Urgency
elective — urgent if flash pulmonary edemaManagement
medical therapy, angioplasty/stenting for FMDBiopsy
Not NeededFollow-up
Doppler US every 6-12 months, CTA/MRA as neededRAS treatment depends on etiology and clinical status. In atherosclerotic RAS, optimal medical therapy (antihypertensive + statin + antiplatelet) is the priority — CORAL trial showed stenting provides no additional benefit. In FMD, angioplasty (without stent) is the first-line treatment with 80-90% success rate. Revascularization is considered for flash pulmonary edema or bilateral stenosis.
Atherosclerotic renal artery stenosis is primarily managed medically after the CORAL trial; stenting is considered only for resistant hypertension, flash pulmonary edema, or progressive renal failure. FMD in young women is treated with angioplasty (good outcomes). Bilateral stenosis can cause severe renovascular hypertension and renal failure.