**4. Doppler ultrasound of renal arteries**

Renovascular hypertension is the second most common cause of secondary hypertension in approximately 2% of adult patients who present with blood pressure elevation when assessed in specialized centres [31]. This is caused by one or more stenoses of the extrarenal arteries, which in the elderly population have frequently an atherosclerotic nature. Fibromuscular dysplasia accounts for up to 25% of total cases and is the most common variety in young adults. Unfortunately there is not any optimal screening test available for the time. A screening test should have a high sensitivity in order to keep the false negative results in the lowest possible level. The Doppler ultrasound of renal arteries allows an analysis of the renal perfusion. According to various studies the sensitivity and specificity of Doppler ultrasound in the diagnosis of renal artery stenosis lies approximately at 90% [32, 33]. Due to the fact that renovascular hypertension in individuals with mild and medium hypertension has a preva‐ lence below 1%, an unselective examination of all individuals with hypertension would lead to a high rate of false positive results. That would result to a high rate of unnecessary angiog‐ raphies. On the other hand in a preselected population of hypertensives with clinical impli‐ cations of increased probability of renal artery stenosis the Doppler ultrasound of the renal arteries is a very appropriate screening examination, due to the fact that the prevalence of renovascular hypertension in acute, severe and resistant hypertension is significantly higher (10-45%). In other words, the use of Doppler ultrasound as a diagnostic tool in a selected population, has a significantly higher positive predictive value with a still acceptable negative predictive value.

today's ultrasound technology it is possible to visualize approximately 88% of all main and accessory renal arteries [35]. In every renal artery angle corrected flow velocity measurements should be performed in at least 5 points. A velocity of 60-100cm/s is considered as normal, whereas a 70% stenosis leads to velocities of at least 180-200cm/s. Stenoses proximal to the ostium are easily obtainable with an epigastric transverse scan and distal stenoses or stenoses of segmental branches are better seen with a longitudinal flank scan (lateral position).

Diagnostic Use of Sonography in the Evaluation of Hypertension

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Additional intrarenal scanning permits the diagnosis of renal artery stenosis without direct imaging of the main renal artery. In 1994, Schwerk *et al*. introduced the Resistive Index (RI) obtained in the interlobar arteries as a reliable indirect parameter for detecting renal artery stenosis. The RI is a ratio of peak systolic and end diastolic velocity, derived from the Doppler spectrum of any vessel. The authors calculated the side-to-side difference of intrarenal RI > 5% with the lower RI in the post-stenotic kidney. Sensitivity and specificity were 100% and 94%, respectively, for moderate and severe RAS [36]. In the meantime, intrarenal RI has been frequently evaluated for different nephrological issues [37, 38]. In a single prospective study a high intrarenal RI was found to be negatively correlated with the outcome of intervention in patients with atherosclerotic renal artery stenosis [39]. A high RI (RI ≥ 80) was felt to reflect advanced renal damage, which would explain the interventional treatment failure. Rader‐ macher et al. [39] investigated the efficacy of angioplasty of a renal artery stenosis in depend‐ ence of the RI. They concluded that an increased renal resistance index > 0.8 is associated with a poor prognosis despite correction of the stenosis. To date, the clinical impacts of these

The carotid wall thickening is an early marker of atherosclerosis and subclinical organ damage. It precedes the evolution of arteriosclerotic plaques. Ultrasound of the carotid arteries constitutes a very good opportunity to evaluate hypertension-induced vascular end organ damage. Several cardiovascular risk factors including male sex, ageing, elevated blood pressure, diabetes, smoking and obesity are positively associated with increased carotid intima-media thickness (IMT) in observational and epidemiological studies. Above these factors, high systolic blood pressures have the greatest effect on IMT [40]. An IMT > 0.9 mm in the common carotid artery is generally seen as abnormal; however there is a continuous relationship between IMT and cardiovascular events. An intima-media thickness (IMT) > 0.9 mm or the presence of a carotid plaque predict the occurrence of stroke and myocardial infarction [2, 41]. Particularly, in a meta-analysis of data from 8 studies in general populations, including about 37,000 subjects who were followed up for a mean of 5.5 years, the risk for a myocardial infarction increases by 10-15% and the stroke risk by 13-18% for every 0.1 mm increase of the IMT [42]. For the assessment of CVD risk, the carotid artery wall, rather than the degree of luminal narrowing, is examined to identify areas of increased thickness and nonocclusive atherosclerotic plaque, which represent early stages of arterial injury and athero‐ sclerosis. Furthermore, the detection of early signs of vascular damage has to include ultrasound not only of the common carotid arteries, but of bifurcations and/or internal carotids

findings are discussed controversially.

**5. Ultrasound of carotid arteries**

Clinical signs for a renovascular hypertension include the following:


It should be mentioned, that a difference of more than 1.5 cm in length between the two kidneys, which is usually considered as being diagnostic for renal artery stenosis is only found in 60 – 70% of the patients with renovascular hypertension [34].

The examination itself can be limited by factors such as bowel gas, obesity, cooperation of the patient and from the fact that it is a highly operator dependent examination. The atherosclerotic induced renal artery stenosis is easily detectable, because it usually involves the ostium and the proximal 1/3 of the renal artery. On the other hand fibromuscular dysplasia involves the distal 2/3 of renal artery and their segmental branches and is thus difficult to depict. With today's ultrasound technology it is possible to visualize approximately 88% of all main and accessory renal arteries [35]. In every renal artery angle corrected flow velocity measurements should be performed in at least 5 points. A velocity of 60-100cm/s is considered as normal, whereas a 70% stenosis leads to velocities of at least 180-200cm/s. Stenoses proximal to the ostium are easily obtainable with an epigastric transverse scan and distal stenoses or stenoses of segmental branches are better seen with a longitudinal flank scan (lateral position).

Additional intrarenal scanning permits the diagnosis of renal artery stenosis without direct imaging of the main renal artery. In 1994, Schwerk *et al*. introduced the Resistive Index (RI) obtained in the interlobar arteries as a reliable indirect parameter for detecting renal artery stenosis. The RI is a ratio of peak systolic and end diastolic velocity, derived from the Doppler spectrum of any vessel. The authors calculated the side-to-side difference of intrarenal RI > 5% with the lower RI in the post-stenotic kidney. Sensitivity and specificity were 100% and 94%, respectively, for moderate and severe RAS [36]. In the meantime, intrarenal RI has been frequently evaluated for different nephrological issues [37, 38]. In a single prospective study a high intrarenal RI was found to be negatively correlated with the outcome of intervention in patients with atherosclerotic renal artery stenosis [39]. A high RI (RI ≥ 80) was felt to reflect advanced renal damage, which would explain the interventional treatment failure. Rader‐ macher et al. [39] investigated the efficacy of angioplasty of a renal artery stenosis in depend‐ ence of the RI. They concluded that an increased renal resistance index > 0.8 is associated with a poor prognosis despite correction of the stenosis. To date, the clinical impacts of these findings are discussed controversially.
