From the Guidelines
No, kidney asymmetry of greater than or equal to 1.5 cm is not diagnostic for renal artery stenosis and does not occur in over two-thirds of patients with renovascular hypertension. While kidney size discrepancy can be a finding in renal artery stenosis due to ischemic atrophy of the affected kidney, it is neither sensitive nor specific enough to be considered diagnostic, as noted in the guidelines for renovascular hypertension 1. Kidney asymmetry can occur in many other conditions including congenital differences, prior infections, trauma, or other vascular abnormalities. Additionally, early renal artery stenosis may not yet have caused significant atrophy. The gold standard for diagnosing renal artery stenosis involves imaging studies such as CT angiography, MR angiography, or conventional angiography, which directly visualize the arterial narrowing, as recommended by the American College of Cardiology and American Heart Association 1. Doppler ultrasound can also be used as a screening tool. Clinical suspicion should be based on factors such as sudden-onset hypertension, hypertension resistant to multiple medications, young age of onset, or abdominal bruits on physical examination, rather than kidney size discrepancy alone. Some key points to consider in the diagnosis and management of renal artery stenosis include:
- The importance of controlling hypertension as part of atherosclerosis risk reduction 1
- The use of percutaneous revascularization for patients with hemodynamically significant renal artery stenosis and accelerated hypertension, resistant hypertension, malignant hypertension, hypertension with an unexplained unilateral small kidney, and hypertension with intolerance to medication 1
- The role of clinical clues, such as resistant hypertension, in identifying patients who may benefit from directed evaluation for renal artery disease 1
From the Research
Diagnostic Criteria for Renal Artery Stenosis
- Kidney asymmetry by greater or equal to 1.5 cm is not explicitly mentioned as a diagnostic criterion for renal artery stenosis in the provided studies 2, 3, 4, 5, 6.
- The studies suggest that diagnostic work-up for hemodynamically significant renal artery stenosis should be restricted to patients suspected to be at moderate or high risk for renovascular disease 2.
- Patients at moderate risk should first undergo a screening test, like Doppler ultrasonography or captopril-enhanced scintigraphy, followed by renal artery imaging with either spiral computed tomography angiography or magnetic resonance angiography with Gadolinium if the screening test is positive 2.
Prevalence of Kidney Asymmetry in Renovascular Hypertension
- There is no direct evidence in the provided studies to suggest that kidney asymmetry by greater or equal to 1.5 cm occurs in over two thirds of patients with renovascular hypertension 2, 3, 4, 5, 6.
- The studies focus on the diagnostic accuracy of various imaging modalities for renal artery stenosis, such as color Doppler US, CT angiography, and GD-enhanced MR angiography, compared to digital subtraction angiography 5.
- A clinical prediction rule for renal artery stenosis has been developed, which can help select patients for renal angiography in an efficient manner 6.
Imaging Modalities for Renal Artery Stenosis
- Computed tomography angiography and gadolinium-enhanced, three-dimensional magnetic resonance angiography are preferred diagnostic tests for patients referred for evaluation of renovascular hypertension 3.
- Color Doppler US, CT angiography, and GD-enhanced MR angiography have been compared in a prospective intraindividual study, with CTA and GD-enhanced MRA showing comparable and satisfactory results with respect to the negative predictive accuracy of suspected renal artery stenosis 5.