When is screening for renal artery stenosis medically necessary?

After diabetes and hypertension, renal artery stenosis is the leading cause of kidney failure. Recent changes in the opinions of nephrologists and cardiologists, as well as new medical guidelines, are increasing doctors’ awareness of the need to screen for it.

"Our aging population, especially older patients with cerebrovascular, cardiac, and peripheral arterial disease increases the frequency of renal artery stenosis," said Dr. Skip Freedman, Executive Medical Director at AllMed Healthcare Management (http://www.allmedmd.com), a leading Independent Review Organization (IRO). "Many doctors are uncertain about the best way to screen for the disease or which patients to screen."

As a result, doctors either unnecessarily screen patients or order expensive and unneeded medical tests. This unneeded screening can result in an increased number of false-positive results. Following up on them often means invasive testing. These extra tests have both an inherent risk and increase the cost of treatment.

For a screening to be medically required, one of these conditions must exist:

• The patient is over 65-years old and diagnosed with high blood pressure (hypertension) for the first time.
• The patient has medically controlled blood pressure that is worsening.
• The patient has an acute kidney injury.
• The patient has a chronic kidney disease that’s not explained by diabetes, volume depletion or some form of vascular disease.

This approach excludes routine screenings for renal artery stenosis in low risk hypertensive patients — for example, a significantly obese young patient with no vascular disease, who also doesn’t have other diseases, such as diabetes or sleep apnoea would not need screening. The inability to control a patient’s hypertension who is not on more than two blood pressure medications doesn’t justify screening IF the patient doesn’t meet one of the above four conditions. Doctors should avoid screening low risk patients because most times the positive results are "false positives" so additional testing only leads down blind alleys.

When one of the reasons to do renal artery stenosis screening is present, a renal artery Doppler is the only initial medical screening needed. While it is less expensive than other tests, its drawbacks include its availability and the ultrasonographer’s skill. Also screening larger patients is more difficult.

For an obese patient whose body-mass-index (BMI) exceeds 35, a doctor might consider imaging for other reasons. In this case, a CT angiogram or magnetic resonance angiography (MRA) of the renal arteries is needed only if the Doppler test returned uncertain results or did not show the renal arteries clearly and is ordered by a cardiologist or nephrologists.

"Only when doctors find and document one of the four conditions in a patient is screening for renal artery fstenosis medically necessary," Dr. Freedman said. "Following these guidelines will help decrease the unnecessary and inappropriate testing for renal artery stenosis, and improve the care of patients with the disease."

(Source: AllMed Healthcare Management: December 2008)