Should adrenal vein sampling be the test for surgical management of primary aldosteronism?
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Simply put, adrenal vein sampling carries high accuracy.
Cross-sectional imaging with CT or MRI does not.
The accurate localization of the unilateral forms of primary aldosteronism is essential for curative surgical intervention. The main reason adrenal vein sampling has been challenged as a gold standard is because many centers fail to successfully collect samples from both adrenal veins. That primarily relates to the lack of dedicated and interested experience of the interventional radiologist. The conclusion is often that adrenal vein sampling is fraught with issues and we should not use it.
In centers like mine, where we have invested time and energy and have a very interested, talented and engaged interventional radiologist, we have a very successful adrenal vein sampling program, happy patients and good outcomes. It is fine if centers say they cannot do it — that is their decision. To apply that across the board to others does not make any sense.
In July I observed adrenal surgery in one of my patients with primary aldosteronism. Adrenal vein sampling localized to the left adrenal gland, but with the CT scan, the adrenal glands looked normal. Our endocrine surgeon took out the left adrenal gland, the pathologist cut it up, and there was a 4-mm tumor. No scan will reliably tell you that your patient has an adrenal tumor that is smaller than one-fifth of an inch. These aldosterone-producing tumors are small but mighty. The accuracy of CT is about 56%. It’s not much better than flipping a coin.
A myth persists among endocrinologists that adrenal vein sampling is too difficult a procedure to be practical and generalizable. That simply is not true. The key is for the endocrinologist to develop a partnership with a single trusted interventional radiologist with a consistent protocol. Technology has also improved, making the process easier than adrenal vein sampling procedures 15 years ago.
Endocrinologists who want to develop an endocrine hypertension or adrenal program need to be able to offer adrenal vein sampling to provide high-level care for patients with primary aldosteronism. It takes dedication and interest. It takes coordinating with the laboratory so that all the samples and dilutions are labeled correctly, and there are no sample mix-ups. It requires engaging an interventional radiologist who recognizes how important successful bilateral sampling is to patient outcomes — someone who will not give up after 15 minutes. Then you need to send patients with primary aldosteronism to that interventional radiologist so they gain experience.
William F. Young, MD, MSc, is an endocrinologist and professor of medicine at the Mayo Clinic College of Medicine in Rochester, Minnesota.
Imaging innovation — and not adrenal vein sampling — will likely provide the way forward in managing primary aldosteronism.
There are several questions to ask when it comes whether adrenal vein sampling should be considered a gold-standard procedure. Is it easy to do? Is it noninvasive? Is it accurate in terms of sensitivity and specificity? Is it standardized and reproduceable? Most important, does it improve clinical outcome? The answer to most of those questions, if not all, is still no.
The term “gold standard” is often used glibly. Adrenal vein sampling is not easy to perform. It is not safe or noninvasive. There is a complication rate, and the radiation exposure through fluoroscopy is six times that of coronary angiography.
For most patients, a pragmatic solution should include considering surgery for patients aged 35 years and younger, and possibly up to age 50 years, when there is a typical adrenal lesion observed on a fine-cut CT scan and the contralateral adrenal gland appears normal. Mineralocorticoid receptor blockade therapy is highly effective as an alternative to surgery, provided a non-suppressed plasma renin activity measurement is used as a biomarker.
We do not need to operate on everybody. The challenge is to address the mass population with this disease, with stratification of this diagnosis enabling effective medical treatment and attacking the wider cardiovascular risk profile. My contention is adrenal vein sampling is rarely indicated. Logistics are also an issue when it comes to adrenal vein sampling. These patients with primary aldosteronism are all over the U.S., not just clustered around a center of excellence. That is the real challenge — making a diagnosis to ensure we can provide the most appropriate therapy and avoid the potential misleading consequences of performing adrenal vein sampling.
Adrenal vein sampling is invasive, hard to do, frequently fails, is costly and is without evidence base in terms of improving outcome for patients with primary aldosteronism. There is no unified agreement over the protocols to be used, nor over its interpretation. So why do it?
Paul Stewart, MD, FRCP, is faculty dean of medicine and health and professor of medicine at the University of Leeds, United Kingdom.
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