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Abdominal Bruits: Sheri A. Keitz, MD, PhD, discusses the clinical examination for abdominal bruits.
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Abdominal Bruits: Sheri A. Keitz, MD, PhD, discusses the clinical examination for abdominal bruits.
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Language: EN.
Segment:0 .
>> I'm Joan Stephenson, editor of JAMA's Medical News and Perspectives section. Today, we'll be hearing from Dr. Sheri Keitz about abdominal bruits, a topic discussed in the Rational Clinical Examination. Dr. Keitz is Vice Chair for Clinical Affairs and Division Chief for General Internal Medicine in the Department of Medicine at the University of Massachusetts Medical School and UMass Memorial Healthcare. Welcome to the podcast, Dr. Keitz. >> Thank you, Joan. >> What is the prevalence of abdominal bruits in the general population and how does it compare with the prevalence in patients with hypertension and in patients with renal stenosis?
>> Abdominal bruits are actually quite common and can be an innocent finding in people without hypertension. We know from published studies that in populations without hypertension, the prevalence of abdominal bruits ranges from about 6.5% to 31%. In patients with hypertension, the prevalence of abdominal bruits is 28%, consistent with that upper end of the range with the general populations. However, studies that looked at patients with angiographically proven renal artery stenosis documented a much, much higher prevalence of abdominal bruits -- somewhere between 78- and 87%.
So, it is not recommended that the physical exam for abdominal bruits be done in the general population. Rather, the exam should be limited to patients with hypertension and patients for whom renal artery stenosis is being considered. >> How should a clinician examine for abdominal bruits? >> Well, the patient should be relaxed and in a supine position with the room quiet and with the examiner initially auscultating in the epigastrium with moderate pressure applied to the diaphragm of the stethoscope.
So, I want to clarify what I mean by moderate pressure. Remember that the distance between the surface and the renal arteries is fairly far, so moderate pressure may be briefly uncomfortable for the patient. The clinician should inform the patient that he or she will need to push down firmly with the stethoscope and ask the patient to relax and try to permit the examination. Once a bruit is detected, the clinician will also need to place the fingers of one hand over the carotid artery to be able to record the timing of the bruit.
Bruits can be correlated to the cardiac cycle by palpation of the carotid upstroke with the systolic-diastolic bruit being more prolonged and extending into diastole. So, next, a word about where to listen. So, following the epigastric area, all four quadrants should be auscultated anteriorly. The auscultation should continue over the spine and flanks in the areas between T12 and L2 to rule out bruits that may be heard best posteriorly.
However, no data exists that supports the routine auscultation of the back for abdominal or retroperitoneal bruits. If you hear a bruit, the location of a bruit can help guide differential diagnosis. Bruits heard in the epigastric area may represent renovascular disease, given that the kidneys lie retroperitoneally and the renal arteries leave the aorta in the area right above the umbilicus. Other processes may be associated with an epigastric bruit that might be pancreatic neoplasm or might be an innocent bruit.
The bruit of hepatic carcinoma has been heard in the right upper quadrant and the bruit related to splenic arterial venous fistula described in the left upper quadrant. Periumbilical bruits are sometimes heard in the setting of mesenteric ischemia and venous hums are from portosystemic hypertension. Finally, in older populations, an abdominal bruit may be associated with an abdominal aortic aneurysm. >> What are the auscultatory characteristics of bruits?
>> So, the physiologic basis of a bruit is turbulent blood flow within a vessel. That can be caused by intrinsic or extrinsic abnormalities and is characterized by pitch, timing with the cardiac cycle (specifically systole or diastole), amplitude, and location. Location, pitch, and intensity may help to differentiate the origin of a bruit, but there's limited data to support specific associations. We would suggest that clinicians not be overconfident in their ability to make specific diagnoses based on the characteristics of an auscultated bruit.
So, in general, high-pitched bruits may be more prevalent with renal artery disease compared to medium- or low-pitched bruits. Louder bruits may be associated with renal artery stenosis. Studies that actually looked at whether a clinician can predict the localization of the stenosis revealed correct localization only about 50% of the time. In the study with the largest correlation, 70% of the time. One of the studies included authors in which they were directly auscultating the artery using a sterile stethoscope in surgery.
So, even within that setting, there was still, you know, limited ability to be overly confident in what you hear. >> What is the accuracy of abdominal bruits for detecting renovascular disease? >> So, we like to use the likelihood ratio as a diagnostic test characteristic that will help move us from a pre-test to post-test probability of disease. In this case, the disease is renal artery stenosis. Conceptually, the likelihood ratio is how much more or less likely is a disease process because of a particular test finding.
So, the likelihood ratio is always calculated and reported for each test result. The presence of a systolic-diastolic bruit was demonstrated in one study to have a positive likelihood ratio of 39. This is a very, very high likelihood ratio which will substantially increase the probability of renal artery stenosis. In the general population, the prevalence of renovascular disease is between 1% and 5%. So, this would be your starting point, or otherwise known as pre-test probability.
The test is listening for a bruit. So, if a clinician were to hear a systolic-diastolic bruit, that would increase the probability of renal artery stenosis from 1% to 5% to between 28% and 68%. So, what if the clinician doesn't hear a systolic-diastolic bruit? Well, there's also a likelihood ratio for not hearing a bruit. In this case, that negative likelihood ratio is 0.62. As for any ratio, a likelihood ratio less than 1 decreases the probability of disease, in this case renal artery stenosis.
So, a likelihood ratio of 0.62 is pretty close to 1, which really is not very different in terms of its ability to move your diagnosis. So, if a clinician were to not hear a bruit, the likelihood would decrease from -- if we take 5% as our starting point -- from 5% to 3%. So, bottom line is that doesn't help you very much. Using those same populations, we could look at a higher-risk population -- patients with medically refractory hypertension.
In this group, 20% of patients have renal artery stenosis. So, our starting point -- that pre-test probability -- is higher. In this higher-risk population, if a clinician hears a systolic-diastolic bruit and you apply that likelihood ratio of 39, the post-test probability of disease climbed to 91%. If the clinician doesn't hear the systolic-diastolic bruit, the probability decreases -- because remember that the likelihood ratio of 0.62 is less than 1 -- but it only decreases a small amount, to about 13%.
One more point about accuracy of abdominal bruits. Three studies, including one very large perspective study of over a thousand patients with hard-to-control hypertension, confirmed the usefulness of the finding of an abdominal bruit even when there's only a systolic component. Remember that that very high likelihood ratio of 39 was for the finding of a systolic and diastolic bruit. For a systolic bruit alone, the [inaudible] likelihood ratio is 4.3, which will still increase the probability of renal artery stenosis when it's heard.
But it increases that number from, let's say, 5% to 18%, or in the higher-risk population from 20% to 52%. >> Is there anything else you would like to tell our listeners about the clinical examination for abdominal bruits? >> So, I would say this is a very timely topic given the recent focus on hypertension management with the publication of the Ace Report on the Joint National Committee on Hypertension that was published in JAMA in February of this year, 2014.
JNC-8 did not directly cover recommendations concerning the clinical exam. Rather, they refer readers back to JNC-7 guidelines, which did recommend auscultation for abdominal bruits in all patients with hypertension. So, while our listeners may be rethinking some aspects of hypertension management, they should continue to examine all hypertensive patients for abdominal bruits. The take-home message is that the finding of any abdominal bruit in a patient with hypertension will increase the likelihood of renal artery stenosis.
>> Thanks very much, Dr. Keitz, for this helpful look at abdominal bruits. Additional information about this topic is available in the Rational Clinical Examination. This has been Joan Stephenson of JAMA talking with Dr. Sherri Keitz about abdominal bruits for JAMAevidence.
Segment:0 .
>> I'm Joan Stephenson, editor of JAMA's Medical News and Perspectives section. Today, we'll be hearing from Dr. Sheri Keitz about abdominal bruits, a topic discussed in the Rational Clinical Examination. Dr. Keitz is Vice Chair for Clinical Affairs and Division Chief for General Internal Medicine in the Department of Medicine at the University of Massachusetts Medical School and UMass Memorial Healthcare. Welcome to the podcast, Dr. Keitz. >> Thank you, Joan. >> What is the prevalence of abdominal bruits in the general population and how does it compare with the prevalence in patients with hypertension and in patients with renal stenosis?
>> Abdominal bruits are actually quite common and can be an innocent finding in people without hypertension. We know from published studies that in populations without hypertension, the prevalence of abdominal bruits ranges from about 6.5% to 31%. In patients with hypertension, the prevalence of abdominal bruits is 28%, consistent with that upper end of the range with the general populations. However, studies that looked at patients with angiographically proven renal artery stenosis documented a much, much higher prevalence of abdominal bruits -- somewhere between 78- and 87%.
So, it is not recommended that the physical exam for abdominal bruits be done in the general population. Rather, the exam should be limited to patients with hypertension and patients for whom renal artery stenosis is being considered. >> How should a clinician examine for abdominal bruits? >> Well, the patient should be relaxed and in a supine position with the room quiet and with the examiner initially auscultating in the epigastrium with moderate pressure applied to the diaphragm of the stethoscope.
So, I want to clarify what I mean by moderate pressure. Remember that the distance between the surface and the renal arteries is fairly far, so moderate pressure may be briefly uncomfortable for the patient. The clinician should inform the patient that he or she will need to push down firmly with the stethoscope and ask the patient to relax and try to permit the examination. Once a bruit is detected, the clinician will also need to place the fingers of one hand over the carotid artery to be able to record the timing of the bruit.
Bruits can be correlated to the cardiac cycle by palpation of the carotid upstroke with the systolic-diastolic bruit being more prolonged and extending into diastole. So, next, a word about where to listen. So, following the epigastric area, all four quadrants should be auscultated anteriorly. The auscultation should continue over the spine and flanks in the areas between T12 and L2 to rule out bruits that may be heard best posteriorly.
However, no data exists that supports the routine auscultation of the back for abdominal or retroperitoneal bruits. If you hear a bruit, the location of a bruit can help guide differential diagnosis. Bruits heard in the epigastric area may represent renovascular disease, given that the kidneys lie retroperitoneally and the renal arteries leave the aorta in the area right above the umbilicus. Other processes may be associated with an epigastric bruit that might be pancreatic neoplasm or might be an innocent bruit.
The bruit of hepatic carcinoma has been heard in the right upper quadrant and the bruit related to splenic arterial venous fistula described in the left upper quadrant. Periumbilical bruits are sometimes heard in the setting of mesenteric ischemia and venous hums are from portosystemic hypertension. Finally, in older populations, an abdominal bruit may be associated with an abdominal aortic aneurysm. >> What are the auscultatory characteristics of bruits?
>> So, the physiologic basis of a bruit is turbulent blood flow within a vessel. That can be caused by intrinsic or extrinsic abnormalities and is characterized by pitch, timing with the cardiac cycle (specifically systole or diastole), amplitude, and location. Location, pitch, and intensity may help to differentiate the origin of a bruit, but there's limited data to support specific associations. We would suggest that clinicians not be overconfident in their ability to make specific diagnoses based on the characteristics of an auscultated bruit.
So, in general, high-pitched bruits may be more prevalent with renal artery disease compared to medium- or low-pitched bruits. Louder bruits may be associated with renal artery stenosis. Studies that actually looked at whether a clinician can predict the localization of the stenosis revealed correct localization only about 50% of the time. In the study with the largest correlation, 70% of the time. One of the studies included authors in which they were directly auscultating the artery using a sterile stethoscope in surgery.
So, even within that setting, there was still, you know, limited ability to be overly confident in what you hear. >> What is the accuracy of abdominal bruits for detecting renovascular disease? >> So, we like to use the likelihood ratio as a diagnostic test characteristic that will help move us from a pre-test to post-test probability of disease. In this case, the disease is renal artery stenosis. Conceptually, the likelihood ratio is how much more or less likely is a disease process because of a particular test finding.
So, the likelihood ratio is always calculated and reported for each test result. The presence of a systolic-diastolic bruit was demonstrated in one study to have a positive likelihood ratio of 39. This is a very, very high likelihood ratio which will substantially increase the probability of renal artery stenosis. In the general population, the prevalence of renovascular disease is between 1% and 5%. So, this would be your starting point, or otherwise known as pre-test probability.
The test is listening for a bruit. So, if a clinician were to hear a systolic-diastolic bruit, that would increase the probability of renal artery stenosis from 1% to 5% to between 28% and 68%. So, what if the clinician doesn't hear a systolic-diastolic bruit? Well, there's also a likelihood ratio for not hearing a bruit. In this case, that negative likelihood ratio is 0.62. As for any ratio, a likelihood ratio less than 1 decreases the probability of disease, in this case renal artery stenosis.
So, a likelihood ratio of 0.62 is pretty close to 1, which really is not very different in terms of its ability to move your diagnosis. So, if a clinician were to not hear a bruit, the likelihood would decrease from -- if we take 5% as our starting point -- from 5% to 3%. So, bottom line is that doesn't help you very much. Using those same populations, we could look at a higher-risk population -- patients with medically refractory hypertension.
In this group, 20% of patients have renal artery stenosis. So, our starting point -- that pre-test probability -- is higher. In this higher-risk population, if a clinician hears a systolic-diastolic bruit and you apply that likelihood ratio of 39, the post-test probability of disease climbed to 91%. If the clinician doesn't hear the systolic-diastolic bruit, the probability decreases -- because remember that the likelihood ratio of 0.62 is less than 1 -- but it only decreases a small amount, to about 13%.
One more point about accuracy of abdominal bruits. Three studies, including one very large perspective study of over a thousand patients with hard-to-control hypertension, confirmed the usefulness of the finding of an abdominal bruit even when there's only a systolic component. Remember that that very high likelihood ratio of 39 was for the finding of a systolic and diastolic bruit. For a systolic bruit alone, the [inaudible] likelihood ratio is 4.3, which will still increase the probability of renal artery stenosis when it's heard.
But it increases that number from, let's say, 5% to 18%, or in the higher-risk population from 20% to 52%. >> Is there anything else you would like to tell our listeners about the clinical examination for abdominal bruits? >> So, I would say this is a very timely topic given the recent focus on hypertension management with the publication of the Ace Report on the Joint National Committee on Hypertension that was published in JAMA in February of this year, 2014.
JNC-8 did not directly cover recommendations concerning the clinical exam. Rather, they refer readers back to JNC-7 guidelines, which did recommend auscultation for abdominal bruits in all patients with hypertension. So, while our listeners may be rethinking some aspects of hypertension management, they should continue to examine all hypertensive patients for abdominal bruits. The take-home message is that the finding of any abdominal bruit in a patient with hypertension will increase the likelihood of renal artery stenosis.
>> Thanks very much, Dr. Keitz, for this helpful look at abdominal bruits. Additional information about this topic is available in the Rational Clinical Examination. This has been Joan Stephenson of JAMA talking with Dr. Sherri Keitz about abdominal bruits for JAMAevidence.
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