Motivation: During this year, I have presumed renal artery stenosis in many people, tested some of them, and found none. Among so many with vascular disease just about everywhere, I have not discovered a single new case of renal artery stenosis. After the last patient in whom I was very sure of finding renal artery stenosis and found myself fooled once more when reading the radiology report, I wondered whether I am using the right test. The first-line test used - at least as far as I can tell from my experience - has been renal ultrasound with doppler. I wondered whether other imaging ways such as MRI might be better.
Paper: Solar, M., Zizka, J., Krajina, A., et. al. "Comparison of Duplex Ultrasonography and Magnetic Resonance Imaging in the Detection of Significant Renal Artery Stenosis." Acta Medica (2011) 54: 9-12.
Methods: In an academic hospital in Prague, 94 patients with high clinical suspicion of renovascular hypertension were examined by duplex ultrasound, MRA with contrast, and angiography. Angiography was performed last. The gold standard was angiography. For ultrasound, significant renal artery stenosis was defined by peak systolic velocity above or equal to 180 cm/sec (usual standard). For MRA and angiography, a cutoff of 60% stenosis was used.
Results:
Cohort: Of the 94 patients, 41 were women. Average age was 60 years with patients taking on average 3.8 anti-hypertensives. The mean systolic pressure was 153 mmHg (standard deviation of 31). About a third had diabetes. Based on angiography, renal artery stenosis was found in 61 kidneys among 186 kidneys examined (atherosclerosis in 58 and additional four had fibromuscular dysplasia - unexplained whether one case of fibromuscular dysplasia was overlap with atherosclerosis or did not cause significant stenosis).
Duplex Ultrasonography: Ultrasonography could be performed successfully in 81 patients (86%). The most common reason for inability was poor imaging quality. For ultrasound (among imaged kidneys), sensitivity: 85%, specificity: 84%. Positive predictive value: 70%, negative predictive value: 92%.
MRA: By MRA, adequate images could be obtained in 93 of 94 patients. Sensitivity: 93%, specificity: 93%. Positive predictive value: 86%, negative predictive value: 97%.
Discussion: Based on this direct comparison of ultrasound and MRA, testing for someone with high pre-test probability of renal artery stenosis should probably proceed by MRA given higher sensitivities. In cases with low to moderate pre-test probability, renal ultrasound may sufficiently decrease the probability. Neither method is, of course, perfect. While this study was done in Prague, it is likely that a regular American population might be more obese and have higher BMI - particularly in patients with sustained hypertension. The adequacy of an ultrasound examination may be further decreased in this group. A misconception that I had was that if an ultrasound examination could be performed well, it is just as good as MRA. But, even among kidneys that could be examined well, the sensitivity of ultrasound was lower than MRA. Some caveats of this study are that this was a single center study and that there is no verification that radiologists examining the MRA were blinded to the results of the ultrasound (although with MRA, more lesions were detected compared to US). So, from now, if I am really suspicious of renal artery stenosis, I will go ahead with the MRA. Maybe, I will find someone with renal artery stenosis.
Paper: Solar, M., Zizka, J., Krajina, A., et. al. "Comparison of Duplex Ultrasonography and Magnetic Resonance Imaging in the Detection of Significant Renal Artery Stenosis." Acta Medica (2011) 54: 9-12.
Methods: In an academic hospital in Prague, 94 patients with high clinical suspicion of renovascular hypertension were examined by duplex ultrasound, MRA with contrast, and angiography. Angiography was performed last. The gold standard was angiography. For ultrasound, significant renal artery stenosis was defined by peak systolic velocity above or equal to 180 cm/sec (usual standard). For MRA and angiography, a cutoff of 60% stenosis was used.
Results:
Cohort: Of the 94 patients, 41 were women. Average age was 60 years with patients taking on average 3.8 anti-hypertensives. The mean systolic pressure was 153 mmHg (standard deviation of 31). About a third had diabetes. Based on angiography, renal artery stenosis was found in 61 kidneys among 186 kidneys examined (atherosclerosis in 58 and additional four had fibromuscular dysplasia - unexplained whether one case of fibromuscular dysplasia was overlap with atherosclerosis or did not cause significant stenosis).
Duplex Ultrasonography: Ultrasonography could be performed successfully in 81 patients (86%). The most common reason for inability was poor imaging quality. For ultrasound (among imaged kidneys), sensitivity: 85%, specificity: 84%. Positive predictive value: 70%, negative predictive value: 92%.
MRA: By MRA, adequate images could be obtained in 93 of 94 patients. Sensitivity: 93%, specificity: 93%. Positive predictive value: 86%, negative predictive value: 97%.
Discussion: Based on this direct comparison of ultrasound and MRA, testing for someone with high pre-test probability of renal artery stenosis should probably proceed by MRA given higher sensitivities. In cases with low to moderate pre-test probability, renal ultrasound may sufficiently decrease the probability. Neither method is, of course, perfect. While this study was done in Prague, it is likely that a regular American population might be more obese and have higher BMI - particularly in patients with sustained hypertension. The adequacy of an ultrasound examination may be further decreased in this group. A misconception that I had was that if an ultrasound examination could be performed well, it is just as good as MRA. But, even among kidneys that could be examined well, the sensitivity of ultrasound was lower than MRA. Some caveats of this study are that this was a single center study and that there is no verification that radiologists examining the MRA were blinded to the results of the ultrasound (although with MRA, more lesions were detected compared to US). So, from now, if I am really suspicious of renal artery stenosis, I will go ahead with the MRA. Maybe, I will find someone with renal artery stenosis.
I was most excited to see this study because among other things, my acquaintance has begun a daily walking program and their symptoms have improved considerably since their training began. Urinary track remedies
ReplyDeleteMy husband was diagnosed with early onset Parkinson's disease at 57.his symptoms were shuffling of feet,slurred speech, low volume speech, degradation of hand writing, horrible driving skills, right arm held at 45 degree angle, things were tough for me, but now he finally free from the disease with the help of total cure ultimate health home, he now walks properly and all symptoms has reversed, he had trouble with balance especially at night, getting into the shower and exiting it is difficult,getting into bed is also another thing he finds impossible.we had to find a better solution for his condition which has really helped him a lot,the biggest helped we had was ultimatehealthhome they walked us through the proper steps,am highly recommended this ultimatehealthhome@gmail.com to anyone who needs help.
ReplyDelete