Renovascular Hypertension: Can We Identify a Population at High Risk? (Featured CME Topic: Hypertension).
ABSTRACT: Renovascular hypertension Renovascular Hypertension Definition
Renovascular hypertension is a secondary form of high blood pressure caused by a narrowing of the renal artery.
Primary hypertension, or high blood pressure, affects millions of Americans. is a common cause of secondary hypertension. However, diagnostic tests are limited by lack of sensitivity and specificity, cost, or invasiveness. Selecting patients with hypertension for evaluation of renal artery stenosis Renal Artery Stenosis Definition
Renal artery stenosis is a blockage or narrowing of the major arteries that supply blood to the kidneys.
Description can be challenging. This review focuses on the sensitivity and specificity of commonly used screening tests for renal artery stenosis and on the clinical variables that are most likely to distinguish patients with renal artery stenosis from patients with other causes of their hypertension. This approach allows for the rational screening of patients at high and moderate risk for renal artery renal artery
An artery with its origin in the aorta and with distribution to the kidney. disease.
RENOVASCULAR HYPERTENSION (RVHT) is one of the most common causes of secondary hypertension, with reports of its frequency varying from less than 1% to as high as 30% in highly selected referral populations.  Its importance lies in the fact that it is a potentially curable cur·a·ble
Capable of being cured or healed. disease that--if left undiagnosed and untreated--may lead to permanent end-stage renal disease End-stage renal disease (ESRD)
Total kidney failure; chronic kidney failure is diagnosed as ESRD when kidney function falls to 5-10% of capacity.
Mentioned in: Chronic Kidney Failure
end-stage renal disease , heart disease, retinopathy retinopathy /ret·i·nop·a·thy/ (ret?i-nop´ah-the) any noninflammatory disease of the retina.
circinate retinopathy , and cerebrovascular disease cerebrovascular disease Neurology Any vascular disease affecting cerebral arteries–eg ASHD, diabetic vasculopathy, HTN, which may cause a CVA or TIA with neurologic sequelae–speech, vision, movement of variable duration. .
Renovascular hypertension refers to hypertension that is caused by renal hypoperfusion due to a flow-limiting vascular stenosis and is corrected by either surgical or percutaneous revascularization. It is important to distinguish RVHT from the much more prevalent condition of renovascular disease (defined as significant stenosis of a renal artery), since one condition frequently exists without the other. Eyler et a1  found that in normotensive normotensive /nor·mo·ten·sive/ (-ten´siv)
1. characterized by normal tone, tension, or pressure, as by normal blood pressure.
2. a person with normal blood pressure. patients over the age of 60, the prevalence of renovascular disease was 45%. Furthermore, the presence of both renovascular disease and hypertension does not necessarily implicate im·pli·cate
tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates
1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot.
2. causality. This is shown by work from Smith  in 1956 who recognized that nephrectomy Nephrectomy Definition
Nephrectomy is the surgical procedure of removing a kidney or section of a kidney.
Nephrectomy, or kidney removal, is performed on patients with cancer of the kidney (renal cell carcinoma); a disease in was able to relieve hypertension in only 35% of patients with documented coexisting renovascular disease and hypertension. However, these data may be partially explained by the fact that the longer the duration of RVHT, the less likely revascularization will be able to effect a cure of hypertension. Amo ng 110 patients who had surgery for RVHT, hypertension improved in 78% of patients with hypertension for less than 5 years, but in only 25% with a longer duration of hypertension. 
Renovascular hypertension results when a vascular stenosis leads to renal ischemia and elevation of renin renin /re·nin/ (re´nin) a proteolytic enzyme synthesized, stored, and secreted by the juxtaglomerular cells of the kidney; it plays a role in regulation of blood pressure by catalyzing the conversion of angiotensinogen to angiotensin I. release from the affected kidney. [5, 6] Renin subsequently leads to angiotensin II angiotensin II
An octapeptide that is a potent vasopressor and a powerful stimulus for production and release of aldosterone from the adrenal cortex. formation, which serves as a powerful vasoconstrictor vasoconstrictor /vaso·con·stric·tor/ (-kon-strik´ter)
1. causing constriction of blood vessels.
2. a nerve or agent that does this.
n. as well as a stimulator of aldosterone secretion with resulting salt and water retention. The central role of the renin-angiotensin-aldosterone axis in the development of hypertension is clearly shown in the profound response of both renal function and blood pressure to the introduction of angiotensin-converting enzyme angiotensin-converting enzyme /an·gio·ten·sin-con·vert·ing en·zyme/ (-ten´sin kon-vert´ing en´zim) see peptidyl-dipeptidase A.
n. (ACE) inhibitors in patients with RVHT. Numerous causes can lead to renovascular disease; the two most common are atherosclerosis and fibromuscular dysplasia Fibromuscular dysplasia
A disorder that causes unexplained narrowing of arteries and high blood pressure.
Mentioned in: Cerebral Aneurysm
fibromuscular dysplasia .  Fibromuscular dysplasia leads to renovascular disease and hypertension through medial fibroplasia fibroplasia /fi·bro·pla·sia/ (-pla´zhah) the formation of fibrous tissue.fibroplas´tic
retrolental fibroplasia (RLF) retinopathy of prematurity. of the renal artery. It is seen most commonly in young females and often involves multiple arteries originating from the aorta.  This review will focus solely on RVHT due to atherosclerosis.
Since 1937, when the first successful report of treating hypertension with nephrectomy was published,  clinicians have struggled to detect those patients with hypertension who have underlying renal artery stenosis (RAS (1) See network access server.
(2) (Remote Access Service) A Windows NT/2000 Server feature that allows remote users access to the network from their Windows laptops or desktops via modem. See RRAS and network access server. ), and in whom correction of RAS will improve blood pressure. Unfortunately, there are four major obstacles to designing a strategy for the accurate and efficient diagnosis of RVHT:
First, clinical features suggestive of RVHT, such as an abdominal bruit bruit (brwe) (brldbomact)
1. a sound or murmur heard in auscultation, especially an abnormal one.
2. sound (3). , are often infrequent and difficult to detect. Furthermore, the reported prevalence of RVHT in patients with these clinical features varies greatly. This lack of specific clinical findings dictates that diagnostic testing must play an important role.
Second, several tests are available for diagnostic evaluation of patients with suspected RVHT. However, the sensitivity, specificity, costs, and potential morbidities of these tests vary widely. In most cases, standardized, prospective comparisons among the available tests are not available.
Third, currently, only patients with clinical features suggestive of RVHT have diagnostic testing. However, the prevalence of RVHT in patients without these features is unknown. A sensitive, specific, and cost-effective screening test is not available.
Finally, as previously mentioned, although RAS is a necessary precondition for RVHT, it is frequently found coincidentally, and our ability to predict the hemodynamic he·mo·dy·nam·ics
n. (used with a sing. verb)
The study of the forces involved in the circulation of blood.
he consequence of a particular renal artery lesion is unclear. Functional tests that can predict the response of a patient's blood pressure to revascularization are not readily available.
Clinicians are concerned with the ability of a test result to discriminate between persons with and without a particular disease. This ability is determined by a test's sensitivity and specificity. Sensitivity refers to the probability that a test will be positive when it is applied to a person with a disease. Specificity refers to the probability that a test will be negative when applied to a person free of disease. Thus, a perfectly sensitive test, if negative, can rule out the disease, while a perfectly specific test, if positive, can rule in the disease. Although sensitivity and specificity are vital in selecting a test, they are not ordinarily what concerns clinicians in making a decision. Rather, it is the probability of a patient having a disease if the test returns positive or negative. The answer to this question guides clinical practice. These values are termed positive and negative predictive values. Jekel et al  thoroughly reviewed these concepts in 1996. Importantly, predictive values, unli ke sensitivity and specificity, are dependent on the prevalence of disease in the population that is undergoing diagnostic testing. For a test with a sensitivity and specificity of 90%, if the prevalence of disease in the tested population is 5%, then the positive predictive value Positive predictive value (PPV)
The probability that a person with a positive test result has, or will get, the disease.
Mentioned in: Genetic Testing
positive predictive value would be approximately 20%. However, if the prevalence of disease increases to 50%, then the positive predictive value is 80% to 90%. Thus, if one can identify a population with a high prevalence of disease before diagnostic testing, the predictive value of the test result becomes more powerful.
This review will focus on the diagnostic tests that are available for the diagnosis of RAS and will review clinical characteristics that can be used to identify a population of high prevalence. The goal is to identify a population with a high prevalence of RAS before further diagnostic testing, thus increasing the predictive value of any chosen diagnostic test. Before embarking on a potentially costly workup work·up
n. Abbr. w/u
A thorough medical examination for diagnostic purposes. for renovascular disease, two primary questions should be considered: (1) Is the patient a suitable candidate for either surgical or percutaneous revascularization? and (2) What is the goal of treatment? Renal artery revascularization can be done for two main reasons: treatment of hypertension and improvement in renal function in ischemic Ischemic
An inadequate supply of blood to a part of the body, caused by partial or total blockage of an artery.
Mentioned in: Antiangiogenic Therapy, Subarachnoid Hemorrhage, Ventricular Fibrillation
ischemic nephropathy nephropathy /ne·phrop·a·thy/ (ne-frop´ah-the) disease of the kidneys.nephropath´ic
analgesic nephropathy . Obviously, if a patient has well-controlled hypertension and stable renal function, it makes little sense to screen for renovascular disease. However, in the patient with difficult to control blood pressure and worsening renal function, diagnostic work-up b ecomes more reasonable.
DIAGNOSTIC TESTS FOR RENAL ARTERY STENOSIS
Two classes of diagnostic tests are used to investigate the presence of RAS and indirectly RVHT. These classes are tests that assess renin release and those that rely on imaging modalities. Reported sensitivities and specificities may vary according to the expertise of the individual institution.
Assessing Renin Release
As previously discussed, since hypersecretion of renin due to renal hypoperfusion is a primary event in the pathogenesis of RVHT, it is not surprising that patients with RVHT have been found to have elevated plasma renin activity Plasma Renin Activity Definition
Renin is an enzyme released by the kidney to help control the body's sodium-potassium balance, fluid volume, and blood pressure. (PRA PRA - PRAgmatics.
The language used by COPS for specification of code generators.
["Metalanguages of the Compiler Production System COPS", J. Borowiec, in GI Fachgesprach "Compiler-Compiler", ed W. Henhapl, Tech Hochs Darmstadt 1978, pp. 122-159]. ).  However, PRA is a complex variable affected by medications, volume status, and numerous other variables.  Furthermore, the PRA may over time decrease in patients with RVHT. (12) Thus, renin levels are generally higher in patients with fibromuscular dysplasia and less useful in elderly patients. (12) For PRA measurements, the reported sensitivity is 57% and specificity is 66%. (12)
To improve the sensitivity and specificity of PRA measurements, investigators have measured PRA after captopril captopril /cap·to·pril/ (kap´to-pril) an angiotensin-converting enzyme inhibitor used in the treatment of hypertension, congestive heart failure, and post–myocardial infarction left ventricular dysfunction. administration. (13) To perform this test, all patients must discontinue diuretics Diuretics Definition
Diuretics are medicines that help reduce the amount of water in the body.
Diuretics are used to treat the buildup of excess fluid in the body that occurs with some medical conditions such as congestive heart and ACE inhibitors for 2 weeks before testing. The PRA level is tested before and then 30 minutes after a captopril dose. A positive test requires three features: a stimulated PRA >12 ng/mL per hour, an absolute increase in PRA of at least 10 ng/mL per hour, and an increase in PRA levels of [greater than or equal] 150% (or [greater than or equal] 400% if the baseline PRA level was <3 ng/mL per hour). This test showed a 96% sensitivity but only a 55% specificity. (13) Thus, when applied to a population with a high prevalence, a negative result has good predictive value, but a positive result does not aid clinical decision-making.
The standard for PRA measurement comes from renal vein sampling. The comparison of renin levels between renal veins (obtained by percutaneous catheterization catheterization
Threading of a flexible tube (catheter) through a channel in the body to inject drugs or a contrast medium, measure and record flow and pressures, inspect structures, take samples, diagnose disorders, or clear blockages. ) uses a ratio of renin levels greater than 1.5 to 1 as abnormal and lateralizing. (14) In a large series, an abnormal ratio was 92% predictive of curability with revascularization; however, 65% of patients with non-lateralizing renin ratios also had curable disease.14 In an effort to improve the sensitivity and specificity of the test, the renal/systemic renin index has been used.15 This allows determination of the functional significance of bilateral lesions. The index is obtained by subtracting the systemic (infrarenal vena cava) PRA from the PRA levels in the renal veins and dividing by the systemic PRA. An index above 0.24 indicates excessive renin production from that kidney, while lower levels are indicative of renin suppression. (15) However, given the invasive nature of these tests and the low specificity, renal vein renin sampling is usually res erved for diagnostic dilemmas.
Ultrasonography ultrasonography /ul·tra·so·nog·ra·phy/ (-so-nog´rah-fe) the imaging of deep structures of the body by recording the echoes of pulses of ultrasonic waves directed into the tissues and reflected by tissue planes where there is a change in . Duplex ultrasonography combines direct visualization of the renal arteries (B-mode) with hemodynamic measurements in the renal arteries (Doppler). Furthermore, ultrasonography allows direct measurement of renal size. The, procedure identifies the abdominal aorta at the level of the renal arteries and records blood velocity at this site, followed by identification and measurements of blood velocity in the renal arteries. Other measurements include those of the renal parenchymal pa·ren·chy·ma
1. Anatomy The tissue characteristic of an organ, as distinguished from associated connective or supporting tissues.
2. velocities from the upper, middle, and lower poles of the kidneys, as well as renal size. The important parameter is the ratio of velocity in the renal artery to that of the aorta. If the ratio is >3.5, this is likely to be associated with a stenosis of >60%. (16) If the renal artery velocity is >180 cm/second, this is also considered abnormal. The test is limited by the experience of the operator and by patient habitus habitus /hab·i·tus/ (hab´i-tus) [L.]
1. attitude (2).
n. pl. (being more difficult in obese patients) and bowel gas. Thus, Doppler ultrasonography of the kidneys is best performed in the early morning after fasting. Reported sensitivity and specificity range from 90% to 95% and 60% to 90%, respectively. (16) In one study, if renal arteriograms were performed on all patients with a positive Doppler ultrasound, a 2.7% false-positive rate was found. (17) A further use of Doppler ultrasonography may be in predicting which patients would benefit from revascularization. (18) The renal resistive index (RRI RRI Radio Romania International
RRI Raman Research Institute
RRI Resource Renewal Institute
RRI Robarts Research Institute
RRI Research Reactor Institute
RRI Renal Research Institute (USA)
RRI Rights and Resources Initiative ) is obtained from Doppler ultrasonography and represents [1 - (end-diastolic velocity/maximal systolic Systolic
The phase of blood circulation in which the heart's pumping chambers (ventricles) are actively pumping blood. The ventricles are squeezing (contracting) forcefully, and the pressure against the walls of the arteries is at its highest. velocity) x 100].
In a recent study, the RRI was predictive in determining response of blood pressure to revascularization. An RRI >80 identified patients with RAS in whom angioplasty or surgery did not improve blood pressure or renal function. Finally, the presence of asymmetric kidney size may be a clue to underlying RAS and renal ischemia. (16)
Captopril-Augmented Nuclear Renography renography /re·nog·ra·phy/ (re-nog´rah-fe) radiography of the kidney.
Radiography of the kidney.
radiography of the kidney. . Renography is performed with radioactive agents that are excreted either by glomerular glomerular /glo·mer·u·lar/ (glo-mer´u-ler) pertaining to or of the nature of a glomerulus, especially a renal glomerulus.
adj. filtration (99Tc-DPTA) or mainly by tubular secretion combined with glomerular filtration (99Tc-MAG3). (19) The latter agent gives a good representation of renal blood flow In the physiology of the kidney, renal blood flow (RBF) is the volume of blood delivered to the kidneys per unit time. In humans, the kidneys together receive roughly 20% of cardiac output, amounting to 1 L/min in a 70-kg adult male. . It is best to withhold ACE inhibitors and diuretics for at least 48 hours before the test. During the test, blood pressure must be closely monitored, since systolic blood pressures <100 mm Hg or mean arterial pressures <70 mm Hg can invalidate the test. (20) Both scintigraphic images and time-activity curves are measured after the injection of the tracer. When used alone, isotopic renograms have a sensitivity and specificity of approximately 75%. (21) However, given the observation that. renal function in an- ischemic kidney could be abruptly worsened after a single dose of an ACE inhibitor, captopril was subsequently used to augment the sensitivity of the scan. (20) Normally, there is rapid uptake, followed by ex cretion of the tracer. However, in the presence of RAS and captopril, there is delayed uptake and excretion. Studies have documented a sensitivity of approximately 83% and a specificity of 93% for detecting RAS >70%. (22) Perhaps more importantly, the renogram re·no·gram
1. A graphic record of the renal excretion of a radioactive tracer that has been injected into the renal system.
2. A radiograph of a kidney. had 93% sensitivity and 100% specificity for predicting blood pressure response to revascularization if the kidney function was normal. (22) The sensitivity and specificity of renograms decline considerably in the face of renal impairment. Thus, patients with elevated creatinine levels (>2.0 mg/dL) are not ideal candidates for this test. (23)
Magnetic Resonance Angiography Magnetic resonance angiography
A noninvasive diagnostic technique that uses radio waves to map the internal anatomy of the blood vessels.
Mentioned in: Cerebral Aneurysm
magnetic resonance angiography . This relatively new technique shows great promise for the diagnosis of proximal (and thus largely athero-sclerotic) RAS. Gadolinium gadolinium (gădəlĭn`ēəm), metallic chemical element; symbol Gd; at. no. 64; at. wt. 157.25; m.p. 1,312°C;; b.p. 3,233°C;; sp. gr. 7.898 at 25°C;; valence +3. , which has a low degree of nephrotoxicity neph·ro·tox·ic·i·ty
The quality or state of being toxic to kidney cells.
nephrotoxicity(ne·fr and can thus be utilized in patients with renal insufficiency, is used as a contrast agent. (24) Reconstructions of images are used to obtain detailed views of the renal arteries. Various small trials have reported sensitivities ranging from 83% to 100% and specificities of 92% to 97% (25, 26) Limitations include the high cost, limited availability, and substantial expertise needed to analyze images. Results for computed tomography with angiography angiography
X-ray examination of arteries and veins with a contrast medium to differentiate them from surrounding organs. The contrast medium is introduced through a catheter to show the blood vessels and the structures they supply, including are similar, but have the down-side of requiring contrast material with the attendant risk of nephropathy. (27)
Renal Arteriography arteriography /ar·te·ri·og·ra·phy/ (ahr-ter?e-og´rah-fe) angiography of an artery or arterial system.
catheter arteriography . This standard diagnostic test has the advantage of allowing for therapeutic intervention at the time of diagnosis. When the famous bank robber Willie Sutton was asked why he robbed banks, he replied, "I rob banks because that's where the money is. Many believe, following the axiom of Willie Sutton, "If you are looking for a lesion, look at the vessel." This axiom is particularly true for patients with highly suggestive clinical features in whom negative results on noninvasive tests would not be sufficient to exclude the possibility of RAS. Three main advantages are (1) arteriography provides an immediate answer; (2) angioplasty can be performed immediately, if needed; and (3) given new digital-subtraction techniques, small volumes of ionic-contrast or gadolinium-carbon dioxide contrast can be used to minimize the risk of contrast nephropathy. (28) However, angiography has significant potential risks, including contrast-induced renal failure, atheroembolism, local puncture site bleeding, p uncture site pseudoaneurysm formation, and anaphylaxis anaphylaxis (ăn'əfəlăk`sĭs), hypersensitive state that may develop after introduction of a foreign protein or other antigen into the body tissues. . (29) Furthermore, angiography is of relatively little value in predicting blood pressure response to an intervention. Measurement of renal artery pressure gradients may hold some promise in this regard. (30)
Table 1 lists the published sensitivities and specificities of these tests. All the diagnostic tests have limitations, ranging from low sensitivity and specificity to high cost and invasiveness. None of these tests could be used to screen an unselected population of hypertensive hypertensive /hy·per·ten·sive/ (-ten´siv)
1. characterized by increased tension or pressure.
2. an agent that causes hypertension.
3. a person with hypertension. patients. For instance, assuming a prevalence of RAS in hypertensive patients of 5%, a test with a sensitivity and specificity of 90%, if positive, would give a positive predictive value of only 20% to 30%. This illustrates the importance of defining clinically a population with a high prevalence of RAS. If we could use clinical factors to identify a population of hyper-tensive patients who had a prevalence of RAS of 50%, then the positive predictive value of this same test would approach 90%.
CLINICAL FEATURES PREDICTIVE OF RENAL ARTERY STENOSIS
Numerous retrospective and prospective studies have attempted to identify clinical factors that could be used to predict whether patients had a high likelihood of atherosclerotic RAS. The first and largest prospective study that examined clinical and radiographic radiographic (rā´dēōgraf´ik),
adj relating to the process of radiography, the finished product, or its use. features of patients with RVHT was the Cooperative Study of Renovascular Hypertension. (31) This study enrolled 2,442 patients with hypertension and subjected them to a battery of tests, including detailed histories and physical examinations, serum chemistries, and diagnostic and therapeutic tests, including renal arteriograms and revascularization, if warranted. From this population, 339 patients with essential hypertension were compared with 175 patients with RVHT, as defined by the presence of RAS and improvement in blood pressure with surgical revascularization. In this study, certain clinical characteristics stood out as highly prevalent in the population with RVHT. These included high-grade retinopathy, abdominal or flank bruits, the presence o f peripheral vascular disease Peripheral Vascular Disease Definition
Peripheral vascular disease is a narrowing of blood vessels that restricts blood flow. It mostly occurs in the legs, but is sometimes seen in the arms. , absence of family. history of hypertension, and recent onset of hypertension, especially after age 50. Laboratory findings that were more common in the population with RVHT included hypokalemia Hypokalemia Definition
Hypokalemia is a condition of below normal levels of potassium in the blood serum. Potassium, a necessary electrolyte, facilitates nerve impulse conduction and the contraction of skeletal and smooth muscles, including the heart. , metabolic alkalosis, and an elevated blood urea nitrogen blood urea nitrogen
n. Abbr. BUN
Nitrogen in the form of urea in the blood or serum, used as a indicator of kidney function.
Blood urea nitrogen (BUN) level (>20 mg/dL).
The frequency of RVHT in patients with high-grade (grade III or IV) retinopathy has been further investigated, Of 123 patients identified with high-grade retinopathy, 93 had renal angiography, and renovascular disease was detected in 31% of these patients. (32) Thus, severe retinopathy seems to identify a patient population at higher risk.
Numerous studies have examined the prevalence of abdominal and flank bruits in patients with hypertension. Proper ausculation requires that the patient be supine and in a quiet room. Since the kidneys are located retroperitoneally, with the renal arteries leaving the aorta just cephalad cephalad /ceph·a·lad/ (sef´ah-lad) toward the head.
Toward the head or anterior section. to the umbilicus umbilicus /um·bil·i·cus/ (um-bil´i-kus) [L.] the navel; the scar marking the site of attachment of the umbilical cord in the fetus.
n. pl um·bil·i·ci
See navel. , auscultation auscultation
Procedure for detecting certain defects or conditions by listening for normal and abnormal heart, breath, bowel, fetal, and other sounds in the body. The invention of the stethoscope in 1819 improved and expanded this practice, still very useful despite the should begin in the epigastrium epigastrium /epi·gas·tri·um/ (ep?i-gas´tre-um) the upper and middle region of the abdomen, located within the sternal angle.epigas´tric
n. pl. and should include all four quadrants. (33) Auscultation should continue over the spine and flanks in the areas between the twelfth thoracic and second lumbar vertebrae. Finally, the bruit needs to be timed to the cardiac cycle and characterized as a systolic, systolic-diastolic, or venous hum. The differential diagnosis of an abdominal bruit other than RAS includes splenic splenic /splen·ic/ (splen´ik) pertaining to the spleen.
Of, in, near, or relating to the spleen.
pertaining to the spleen. arteriovenous fistula, hepatic cirrhosis, hepatoma hepatoma /hep·a·to·ma/ (hep?ah-to´mah)
1. a tumor of the liver.
2. hepatocellular carcinoma (malignant h.).
n. pl. , abdominal aortic aneurysm abdominal aortic aneurysm A focal aortic dilation of ≥ 50% ↑ in diameter, accompanied by distension and weakened aortic wall Epidemiology Incidence is rising 12/105–1951; 36/105 , celiac artery compression syndrome, intestinal ischemia, and pancreatic carcinoma. (33) Abdominal bruits have a prevalence of 6.5% to 31% in the healthy population, (34) and a prevalence of 28% in patients with all-ca use hypertension. (35) However, in patients with angiographically proven RAS, the prevalence ranges from 78% to 87% (33) Two studies have investigated the sensitivity and specificity of finding a systolic-diastolic abdominal bruit in the diagnosis of RAS. (33) Sensitivity ranged from 39% to 63%, with specificity of 90 % to 99%. Thus, the presence of a systolic-diastolic bruit is highly suggestive of RAS and should be screened for, while the absence of a bruit does not exclude RAS.
As expected, RAS is prevalent in patients with underlying peripheral vascular disease. In an analysis of 300 autopsies, in those cases with aortic aortic
pertaining to or emanating from the aorta. See also aortic arch.
occurs most often in dogs, where it is caused by Spirocerca lupi larvae, turkeys and primates, causing dyspnea, cyanosis and coughing. atherosclerosis, the prevalence of reno-vascular disease was 40%. (36) Furthermore, 33% of patients having abdominal aortography aortography /aor·tog·ra·phy/ (a?or-tog´rah-fe) radiography of the aorta after introduction into it of a contrast material.
n. for either peripheral vascular disease or aortic aneurysm were found to have clinically unsuspected RAS. (37) Finally, 1,235 patients having cardiac catheterization had concurrent angiography, and 187 patients (15.2%) had significant RAS, with 93 patients having lesions > 76%. (38) Only half of this population had hypertension, and none had clinically suspected RVHT. Factors in this study that were predictive of RAS included older age, peripheral vascular disease, coronary artery disease coronary artery disease, condition that results when the coronary arteries are narrowed or occluded, most commonly by atherosclerotic deposits of fibrous and fatty tissue. , congestive heart failure congestive heart failure, inability of the heart to expel sufficient blood to keep pace with the metabolic demands of the body. In the healthy individual the heart can tolerate large increases of workload for a considerable length of time. , serum creatinine > 1.4 mg/dL, female sex, and smoking.
Few prospective studies use clinical criteria alone to select patients for renal arteriography. Svetky et al, (39) in 1990, studied 100 hypertensive patients with renal arteriography who met any one of six entry criteria. These included abdominal or flank bruit, refractory hypertension (blood pressure > 160/95 mm Hg while receiving three or more medications), accelerated hypertension (increase in blood pressure of > 15% in 6 months), severe hypertension (diastolic blood pressure Diastolic blood pressure
Blood pressure when the heart is resting between beats.
Mentioned in: Hypertension > 115 mm Hg or high-grade retinopathy), recent-onset (within the last 2 years) hypertension, and onset of hypertension before age 25 or after age 45. In this study, the only prospective feature that was predictive of RAS that met statistical significance was the presence of an abdominal bruit. There was a trend toward refractory hypertension being statistically significant.
In 1998, Dutch investigators analyzed the clinical characteristics of 477 patients with either drug-resistant hypertension (mean diastolic blood pressure >95 mm Hg on three visits while treated with either amlodipine/atenolol or enalapril/hydrochlorothiazide, or the requirement of three antihypertensives) or an increase in the serum creatinine level to >0.23 mg/dL while receiving an ACE inhibitor. (40) The patients were subjected to renal angiography, and the clinical characteristics of the population were analyzed to determine a clinical predictive score for the probability of renovascular disease. Renal artery stenosis was found in 22% of these patients, 84% of whom had atherosclerotic disease and 25% of whom had bilateral RAS. Univariant and multivariant analyses were done on clinical variables and their association with RAS and a scoring index was formed. Not surprisingly, the most informative variables were the presence of an abdominal bruit, an elevated serum creatinine concent ration, obesity, smoking, and advanced age. This scoring index was used to determine a predicted probability of RAS. A 70-year-old female smoker with an abdominal bruit and a body mass index >25 kg/[m.sup.2] who had drug-resistant hypertension would have a predicted probability of RAS of approximately 50%. Unfortunately, this scoring system has not yet been validated in a large number of patients. However, its potential usefulness can be seen in Table 2. By increasing the pretest probability, analysis of clinical variables allows a positive captopril renogram to be more informative. Furthermore, if validation of a scoring system can be determined, then clinicians may be able to reliably determine a level of pretest probability in which it is both safe and cost-effective to begin with invasive diagnostic testing.
Renovascular hypertension is a common cause of secondary hypertension. Its importance lies in the fact that it is potentially correctable, but the diagnosis requires invasive and expensive tests. Thus, it is imperative that patients at highest risk for RVHT be selected from the hypertensive population. Doing so renders noninvasive diagnostic testing more informative. Kaplan (41) published an algorithm for the diagnosis of RVHT that allows for clinical suspicion of RVHT to guide diagnostic testing. In his algorithm, patients at highest risk should have angiography, while those with moderate risk should have captopril renography or duplex ultrasonography (depending on the expertise of the institution). How should we best define patients who are at high or moderate risk for RVHT? Clinical studies indicate the best predictors are abdominal or flank bruit, high-grade retinopathy, peripheral vascular disease elsewhere, hypertension refractory to treatment with three antihypertensive antihypertensive /an·ti·hy·per·ten·sive/ (-ten´siv) counteracting high blood pressure, or an agent that does this.
Reducing high blood pressure.
n. agents, and elevated serum creat inine level. Patients with any of these features should be screened for RVHT using a noninvasive test. The best test often depends on the expertise of the institution, but the best options are duplex ultrasonography, captopril-renogram, or magnetic resonance angiography. Patients with more than three of these clinical features are at high risk and represent a group that may benefit from immediate renal angiography (Table 3). No diagnostic test should be offered without a thorough clinical assessment and determination of risk. The lack of sensitivity and specificity of these diagnostic tests yields little predictive information in unselected hypertensive patients. Unfortunately, we still are unable to accurately predict which patients with hypertension will benefit from revascularization, though measurement of renal artery pressure gradients and renal resistive resistive /re·sis·tive/ (re-zis´tiv) pertaining to or characterized by resistance. indices may prove useful in the future.
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ce·li·ac or coe·li·ac
Of or relating to the abdomen or abdominal cavity.
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TABLE 1. Sensitivities and Specificities of Diagnostic Tests for Renal Artery Stenosis Test Sensitivity Specificity Likelihood Ratio Renogram 75% 75% 3.0 Captopril renogram 83% 93% 11.8 Peripheral renin level 57% 66% 1.7 Captopril-augmented 96% 55% 2.1 plasma renin activity Ultrasonography Any lesion 95% 90% 9.5 Lesion > 60% 90% 62% 2.4 MR angiography 88%-95% 94% 14.7 TABLE 2. Influence of Determining the Prevalence of Disease on the Posttest Probability for Renal Artery Stenosis Posttest Probability for Prevalence Test Likelihood Ratio 5% 15% Renogram 3.0 15% 30% Captopril Renogram 11.8 35% 60% Posttest Probability for Prevalence Test 30% 50% Renogram 55% 75% Captopril Renogram 85% 90% TABLE 3. Risk of Renovascular Hypertension Based on Clinical Features Moderate Risk (10% to 20%) High Risk (> 20%) Any one or two of the following Any three of the following Abdominal or flank bruit High Grade retinopathy Signs or symptoms of peripheral vascular disease Hypertension refractory to 3 or more medications Elevation of serum creatinine after ACE inhibitor (*) Serum creatinine > 1.4 mg/dL Age > 60 Incidental finding of asymmetrically sized kidneys (*)Must exclude rise in serum creatinine due to volume depletion, hypotension, or concomitant diuretic use. (42)