History and physical examination are important for screening patients with RVH. Some literature indicates that the following symptoms are observed in patients with RVH: irritability or insufficient feeding in infants or headache, fatigue, chest pain, dyspnea, blurred vision, nausea, abdominal pain, and dizziness in pediatric patients [9,12]. However, RVH does not present with specific symptoms, making it need to measure blood pressure and conduct a thorough examination. In these patients, additional history should be collected including a detailed description of all symptoms and perinatal, nutritional, psychosocial, family, and medication history. The healthcare provider should also ask the adolescent about use of oral contraceptives, anabolic steroids, and recreational drugs. For physical examination, it is recommended to measure blood pressure in bilateral arm and leg during the first assessment, and to include anthropometric measurements [13]. Blood pressure in the lower extremities is usually 10%–20% higher than in the upper extremities [14]. Higher blood pressure in the upper extremities may be a sign of aortic stenosis and TA. Abdominal bruit usually indicates turbulent blood flow within an artery, often due to blockage or narrowing. It is known to common cause includes RAS. The child's height, weight, calculated body mass index, and age percentile are helpful in determining the individual blood pressure status [15].

All patients confirmed with hypertension are recommended to undergo screening tests, including urinalysis, complete blood count, chemistry panel including electrolytes, blood urea nitrogen, creatinine, fasting plasma glucose, and a lipid profile (fasting or non-fasting to include high-density lipoprotein and total cholesterol) [5,16]. In a recent study, only 11% of patients with high blood pressure or hypertension underwent the recommended tests [17]. For patients with RVH, the aldosterone to plasma renin activity (PRA) test is necessary to screen for hyperaldosteronism. For renin and aldosterone testing, patients taking angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) should temporarily discontinue the medication. If needed antihypertensive medication is changed, known to least interfering drugs are calcium antagonists, alpha-blockers, hydralazine, and possibly moxonidine [18]. Renin and aldosterone testing is conducted early in the morning under free sodium intake conditions, providing consistent baseline values. Baseline measurements are taken in the supine position, with known normal ranges from infants to adults. If possible, blood samples should be collected after being in the supine position and again after standing for at least 10 minutes to evaluate the changes in renin and aldosterone levels due to postural variations. According to a recent study, in patients with previously diagnosed RAS, aldosterone to PRA ratio <0.5 is likely to represent unilateral RAS, while a ratio of 3.7 or more is likely due to bilateral RAS. It is thought that these differences will arise from the following causes. Unilateral RAS, the normal function of the contralateral kidney results in relatively minor variations in renin and aldosterone levels. However, in bilateral RAS, significant increases in renin secretion from the juxtaglomerular apparatus on both sides lead to a substantial rise in aldosterone levels. Therefore, it has been reported that PRA values can be useful in suspecting unilateral versus bilateral RAS [19]. Secondary hypertension in children is mostly due to rare causes, and it is difficult to obtain meaningful results even if tests are performed. Thus, physicians tend to perform selective tests based on symptoms. However, since early diagnosis can have a significant impact on the patient's progress, it is necessary to properly perform the tests recommended in the guidelines.

Imaging is essential to diagnose RVH, especially in children, in whom the diagnosis is more challenging due to their smaller blood vessels and lack of cooperation. Compared with studies in adults, the evidence in children is limited, and there is no consensus on the best method for diagnosing RVH. Doppler renal ultrasound is used as a first-line screening test for renal artery disease. However, more detailed diagnosis requires cross-sectional imaging using computed tomography angiography or magnetic resonance angiography [20]. If RVH is strongly suspected clinically but cannot be diagnosed by noninvasive methods, renal artery angiography is currently the gold standard diagnostic method [21]. However, it is not used initially for diagnosis because it is very invasive, expensive, time-consuming, and carries risks that may arise during the procedure. In addition to diagnostic purposes, renal artery angiography is performed for therapeutic purposes when surgery or percutaneous coronary angioplasty is anticipated. Among the examination methods, magnetic resonance angiography has limited value when the causative disease is suspected to be FMD because the lesions are often located in the middle and distal areas, which may not be well visualized by this method. In clinical practice, the sensitivity and specificity of each test should be considered and the test method should be selected according to the patient's age (Table 2).

Family history is always important in pediatric patients [10,22]. For example, two Korean studies on patients with RVH showed a high frequency of MMD among the causative diseases: five of 16 (31.3%) in one study and 10 of 25 (40.0%) in the other [9,10]. The imaging characteristics of 25 patients with RVH indicated that RAS predominantly occurred in the proximal orifice region and lacked the beaded appearance seen in FMD. Retrospective genetic analyses of patients with RAS of unknown etiology or presumed FMD and TA revealed other causal mutation-associated genes, such as RNF213 (associated with MMD), GATA6 (associated with cardiac outflow tract obstruction), ELN (associated with Williams syndrome, pulmonary stenosis, and aortic stenosis), JAG1 (associated with Alagille syndrome), GLA (associated with Fabry disease), and SMAD6 (associated with bicuspid aortic valve, aortic stenosis, and aortic aneurysm) [5,23]. For instance, RVH due to RNF213-related vasculopathy was reported in Korean children and adolescents and in Japan [24]. In this way, genetic testing can be useful in diagnosing the underlying disease in idiopathic RVH of unknown etiology. Also, genetic testing, in addition to vascular imaging findings, is expected to be helpful in the management of pediatric patients in whom invasive histological diagnosis is difficult.