Renovascular hypertension is a type of secondary hypertension, where high blood pressure develops secondary to renal artery disease.
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Epidemiology
Approximately 2.5% (range 0.5-5%) of hypertensive patients will have renovascular hypertension as a cause 2,3.
Pathology
Etiology
There are a number of conditions that can cause renovascular hypertension 1-3:
- atherosclerotic renal artery stenosis (~90%)
- fibromuscular dysplasia (second most common)
There are other causes that can cause renal artery obstruction but these are much rarer 2,3:
- renal artery dissection (e.g. from trauma or aortic dissection)
- renal infarction
- Page kidney
- renal artery embolism or thrombosis
- EVAR stent graft
- encircling tumor (e.g. pheochromocytoma)
- radiation-induced fibrosis
- polyarteritis nodosa
Radiographic features
Nuclear medicine
The appearance of renovascular hypertension on nuclear renography will differ depending on the radionuclide used and will trace glomerular filtration rate (GFR) or tubular secretion, or both.
In cases of significant renal artery stenosis, nuclear renography may appear abnormal, however, in less severe cases it may appear normal due to physiologic homeostasis of the renin-angiotensin axis. As such, imaging is typically performed with both a baseline renogram as well as a captopril renogram. In patients with renovascular hypertension, the ACE inhibitor will prevent modulation of the efferent vasculature and GFR will drop in the affected kidney. For radiotracers with tubular secretion, tracer will build up in the kidney, but the drop in GFR will prevent it from being drained into the bladder and the radiotracer will continue to accumulate 4.
Treatment and prognosis
Treatment of the underlying cause has variable effect 2. Renovascular hypertension can lead to ischemic nephropathy and end-stage renal failure 3.
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