Approximately 5% of Americans with hypertension suffer from renal artery stenosis. Atherosclerotic ischemic renal disease accounts for most cases of renal artery stenosis. It typically occurs among persons over 45 years of age with additional risk factors such as CKD, diabetes mellitus, and tobacco use. Fibromuscular dysplasia is a less common cause of renal artery stenosis that most commonly occurs in young women.
Patients with atherosclerotic ischemic renal disease may have refractory hypertension, new-onset hypertension (in an older patient), pulmonary edema with poorly controlled blood pressure, and AKI upon starting an ACE inhibitor or ARB. Physical examination may reveal an audible abdominal bruit on the affected side. Unexplained hypertension in a woman younger than 40 years should raise suspicion for fibromuscular dysplasia.
BUN and serum creatinine may be elevated if there is significant renal ischemia. Patients with bilateral renal artery stenosis may have hypokalemia, a finding that reflects activation of the renin-angiotensin-aldosterone system in response to reduced blood flow (a “prerenal” state).
Abdominal ultrasound can reveal either asymmetric kidney size if one renal artery is affected more than the other or small hyperechoic kidneys if both are affected.
Screening with Doppler ultrasonography, CT angiography, or magnetic resonance angiography (MRA) is recommended if a corrective procedure would be performed when a positive test result is found. Doppler ultrasonography is highly sensitive and specific (85% and 92%, respectively) and relatively inexpensive but is extremely operator and patient dependent, and may be a poor choice for patients who are obese, unable to lie supine, or have interfering bowel.
CT angiography consists of intravenous contrast injection with digital subtraction arteriography. The sensitivities from various studies range from 77% to 98%, with specificities of 90–94%.
MRA is an excellent but expensive way to screen for renal artery stenosis, particularly in those with atherosclerotic disease. Sensitivity is 77–100% and specificity ranges from 71% to 96%. Turbulent blood flow can cause false-positive results. The imaging agent for MRA (gadolinium) has been associated with nephrogenic systemic fibrosis, which is discussed elsewhere under Nephrogenic Systemic Fibrosis.
Renal angiography is the gold standard for diagnosis, but it is more invasive than the three screening tests discussed above. Thus, it is performed after a positive screening test. CO2 subtraction angiography can be used in place of dye when the risk of dye nephropathy exists—eg, in diabetic patients with kidney injury. Lesions are most commonly found in the proximal third or ostial region of the renal artery. The ...