Renal Artery Ultrasound Diagnosis
The kidneys not only eliminate waste, but are integral to electrolyte balance, homeostatic hydration, and blood pressure control. Renal artery ultrasound is indicated in
- Hypertension: when secondary causes are suspected (i.e., not “essential” hypertension): suspected renovascular hypertension.
- Elevated serum creatinine levels: when stenosis threatens the entire kidney.
- Atherosclerosis: 70-80% occlusions can lead to renal tissue hypoxia.
- Back pain attributable to renal disease
- Electrolyte disturbances: Such as hyperkalemia, hyperphosphatemia, hypocalcemia, etc., and associated metabolic acidosis.
- Computations of renal “resistive index”: A pre-operative measurement comparing systolic blood flow velocity with end-diastolic velocity, which correlates well with a predicted benefit of planned revascularization surgery.
Renal artery ultrasound is also part of a global assessment of kidney anatomy, which can distinguish differences in size between the pair when unilateral kidney disease is present. A perusal for calcifications and obstruction of the urinary tract is easily included when renal artery ultrasound is performed. Because renal artery ultrasound is not as sensitive as confirmatory imaging methods, such as CT and MRI, a negative result is not necessarily reassuring, but indicative of the necessity for the more involved imaging that uses contrast.
Other Imaging Used in Renal Artery Disease
While renal artery ultrasound is useful as a screen or for initial investigation into renal artery disease, from atherosclerotic obstructions to renal artery hypertension, confirmation is via more invasive methods.
- CT Arteriography: Invasive due to its intravenous contrast is highly accurate for and confirmatory of atherosclerotic renovascular disease
- Magnetic Resonance Arteriography: Used less often due to concerns with renal sensitivity to the contrast medium used (gadolinium)
Blood tests are generally non-specific in identifying any exact type of kidney disease, but they can indicate global kidney dysfunction when impairment reaches a threshold beyond which results become worrisome. Some components (e.g., serum creatinine) are useful for serial monitoring of disease stability or progression.