When Renal Artery Stenosis Screening is Medically Necessary

Renal artery stenosis is a common cause of hypertension, most commonly causing a worsening of blood pressure control in patients with underlying essential hypertension. It also commonly causes progressive renal disease and is likely to be the third most common cause of end-stage renal disease, following diabetes and hypertension.

Renal artery stenosis has become more prevalent and has been diagnosed much more commonly in recent years. This increase in incidence may be mostly attributed to an aging population, especially those patients with cerebrovascular, cardiac and peripheral arterial disease who have been the beneficiaries of current pharmaceutical agents and newer, more widely available percutaneous interventions.

National medical guidelines, a greater awareness in the medical community, and the opinions of leaders in the cardiology and nephrology communities have increased physicians’ awareness of the need for screening for renal artery stenosis. Many physicians feel uncertain about how to best screen for the disease or which patients to screen. As a result, many patients are screened unnecessarily. Unnecessary screening, however, can result in an increased number of false-positive results that require follow-up with more invasive testing. Additionally, more expensive initial studies than are necessary are commonly ordered without medical justification.

A physician should consider testing for renal artery stenosis when at least one of the following is present:

• new onset hypertension in a patient over 65
• lack of blood pressure control in patients with previously well-controlled hypertension
• acute kidney injury or chronic kidney disease otherwise unexplained by comorbidities such as diabetes or volume depletion
• the presence of other forms of vascular disease

At least one of these conditions should be present for a screening study to be medically necessary. Screening for renal artery stenosis in hypertensive patients who are at a low risk for having renal artery stenosis yields a low return.  For example, screening is not medically necessary in young patients with significant obesity and other related diseases (i.e. diabetes, sleep apnea) if they have no known vascular disease. Likewise, suboptimal control in a patient who has been treated with two or fewer antihypertensive agents is not typically a medical justification for screening for renal artery stenosis in the absence of the criteria listed above. In these cases, screening studies for renal artery stenosis would be considered experimental or investigational.

Screening for renal artery stenosis can be accomplished in the majority of patients with a renal artery doppler, which is much less expensive than other screening modalities. Significant obesity in the patient being screened, availability of the testing, and the skill variability among ultrasonographers are the primary drawbacks to the utility of a screening study. That said, only significant obesity (a BMI above 35) is an indication for an imaging study for screening other than a renal artery doppler. Despite this, the renal arteries cannot be sufficiently visualized in some patients who are not excessively obese.

Many physicians choose to screen patients for renal artery stenosis with a CT angiogram or an MRA (magnetic resonance angiography) of the renal arteries. Neither of these studies should be considered medically necessary for screening renal artery stenosis unless the patient’s BMI is above 35 and the physician feels that the doppler test will be of low yield, if a previously-performed renal artery doppler provided an equivocal reading for renal artery stenosis, or if the patient’s renal arteries could not be sufficiently visualized on renal arteriogram.

Once renal artery stenosis is identified on a screening study, a renal arteriogram can be performed when appropriate. Even if a stenotic lesion is found in a patient who has excellent blood pressure and a long period of stable renal function, intervention may not be necessary because it may not improve blood pressure control or renal function. Additionally, after percutaneous intervention most patients with renal artery stenosis still have hypertension. It is more common for a patient to require one or two fewer antihypertensive agents to maintain blood pressure control. Likewise, the most common scenario in patients with chronic kidney disease following percutaneous intervention is a mild improvement in or stabilization of renal function. It is likely that small-vessel ischemic renal disease still drives the blood pressure elevation to some degree and is responsible for intrinsic (as opposed to prerenal) renal failure. Due to the complexity of the decision making process, a renal arteriogram with or without percutaneous intervention should be found medically necessary if ordered by a cardiologist or nephrologist.

One of the above four clinical scenarios should be documented for any screening study for renal artery stenosis to be medically necessary. When at least one of the four criteria for screening for renal artery stenosis discussed above is present, a renal artery doppler is the only medically necessary screening study, unless the patient has a BMI above 35. A CT angiogram or MRA of the renal arteries should be found medically necessary only if an equivocal result is obtained or the renal arteries are not sufficiently visualized on renal artery doppler. A renal arteriogram would be medically necessary only if ordered by a cardiologist or nephrologist.

These guidelines should help reduce the volume of unnecessary and inappropriate studies ordered to assess for renal artery stenosis while improving the level of care for patients who justifiably should be screened for the disease.