The diagnosis of renovascular disease in children with hypertension is critical as interventional treatment may be curative. The known limitations of radiation exposure and the need to be still during angiographic imaging are magnified in the pediatric population. Unfortunately, pediatric renovascular ultrasound (RVU) is not universally available and has been reported to have low sensitivity and specificity for the detection of renal artery stenosis (RAS). Given this, the primary role of RVU may be to measure renal sizes, assess for nonvascular causes of hypertension, or assess for RAS in children with low probability of renovascular hypertension. On occasion, adult vascular laboratories may be asked to perform pediatric RVU, and there are important differences to consider: lesion pathology, lesion location, and diagnostic parameters for determining lesion severity.
The primary cause of RAS in adults is atherosclerosis. The typical location of plaque is at the origin, and RVU would reveal velocity elevation and turbulence in this area ( Figure 1 A). Generally accepted criteria for a significant stenosis include a peak systolic velocity (PSV) >200 cm/sec with evidence of poststenotic turbulence, and a renal artery to aorta PSV ratio (RAR) >3.5. In contrast to adults, the most common cause of RAS in children is fibromuscular dysplasia (FMD) which may affect the main renal artery or the intrarenal branch arteries. FMD has a tendency for the mid and distal artery ( Figure 1 B) resulting in velocity shifts, turbulence, and often, evidence of beading ( Figure 1 C). There are no validated velocity criteria for determining degrees of stenosis in FMD. Other causes of renovascular hypertension in children include arteritis, aortic coarctation, renal vein thrombosis, and syndromes such as neurofibromatosis.
