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Second case of adrenal mass hypokalemia
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A 54-year-old woman was referred for the evaluation of an adrenal tumor with a history of hypertension since age 29 years and hypokalemia during the past 7 to 8 years. She was seen in the ED for abdominal pain.
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A CT scan with contrast identified a large ventral hernia as the cause of her pain and a 1.8 cm × 2.4 cm right adrenal nodule (Figure 1A). Her blood pressure was 158 mm Hg/84 mm Hg with a pulse of 60 bpm while taking atenolol 50 mg twice daily, nifedipine 60 mg 24-hour tablets daily and potassium chloride 20 mEq twice daily.
Laboratory testing showed the following: serum sodium 141 mmol/L; blood urea nitrogen 13 mg/dL; creatinine 0.66 mg/dL; potassium 3.6 mmol/L; chlorine 102 mmol/L; carbon dioxide 27.8 mmol/L; and aldosterone 42 ng/dL with a plasma renin activity (PRA) of 0.5 ng/mL/hour.
The serum aldosterone/PRA ratio was elevated at 84, consistent with primary aldosteronism. A repeat CT of the abdomen without contrast reported a normal-appearing left adrenal gland and a 2 cm × 1.9 cm right adrenal mass with low attenuation of 6.6 Hounsfield units (Figure 1B), consistent with a benign adrenal adenoma. Although the radiology report commented on a “normal” left adrenal gland, it appeared to be mildly “plump” to the endocrinologist (Figure 1).
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Aorta (Ao), inferior vena cava (IVC). All figures reprinted with premission from:
Stephanie L. Lee, MD, PhD |
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Bilateral adrenal vein sampling was performed with continuous IV cosyntropin 50 mcg/hour started 30 minutes before the procedure. A catheter was placed in the right femoral vein with fluoroscopic guidance to inferior vena cava (IVC), then into the right renal and right adrenal veins. A second catheter was placed in the IVC, then into the left renal vein and left adrenal vein (Figure 2).
Venogram of the right adrenal vein showed multiple venous branches draping around the right adrenal mass, whereas the venogram of the left adrenal was normal (Figure 3A, 3B). Venous blood samples were obtained from the right and left adrenal veins and the IVC and analyzed for aldosterone and cortisol. The cortisol ratio of the right adrenal vein to IVC (28.9) and the left adrenal vein to IVC (30) were identical (see Table below), which proves that both catheters were appropriately placed and drained in both adrenal glands. The aldosterone/cortisol ratio from the right adrenal vein (0.14) was the same as the left adrenal vein (0.21; Table).
This nonlateralizing test result is consistent with bilateral aldosterone secretion and a nonsecreting adrenal adenoma. She was treated medically instead of surgically. After starting spironolactone 50 mg daily, an aldosterone receptor antagonist, her BP is well controlled on this single agent, and her potassium is stable in the low 4s without supplementation. She had a repeat adrenal CT scan 2 years later showing the absence of growth of the low attenuation adrenal nodule consistent with a benign nonsecreting adrenal adenoma.
As discussed in the previous Imaging Analysis article in the March 2012 issue of Endocrine Today, primary aldosteronism should be considered when hypertension is associated with hypokalemia and/or resistant to medical therapies. In contrast to the primary aldosteronism caused by a unilateral adrenal aldosteronoma described in the March article, this patient has bilateral adrenal hyperplasia (BAH) with excess aldosterone secreted from both adrenal glands. She would not have benefited from adrenal surgery and should be treated medically with an aldosterone receptor blocker.
Initial radiologic investigation in the workup of primary hyperaldosteronism is high-resolution, thin-slice (2 mm-2.5 mm) adrenal CT scanning with contrast. Aldosteronomas tend to be small and may not always be seen on CT or MRI scans. In a systematic review, it has been estimated that CT and MRI scans would misdiagnose assigning unilateral vs. bilateral aldosterone secretion in 37.8% of patients. This error would lead to an inappropriate adrenalectomy in 14.6% of the patients, an inappropriate exclusion from adrenalectomy in 19.1% of patients and adrenalectomy on the wrong side in 3.9% of patients.
Adrenal venous sampling was first proposed more than 40 years ago by James Melby, MD, of Boston University Medical Center, to distinguish between BAH and a unilateral aldosteronoma. The accuracy of the test is more than 95% when the procedure is technically successful. The procedure must be performed by an experienced and skilled radiologist. The cannulation of the right adrenal vein is particularly difficult because of its small size. The complications of this procedure occur in about 2.5% or less of studies; they include adrenal hemorrhage or infarction and adrenal vein thrombosis but appear to be less common when smaller volumes of contrast are used.
The aldosterone-to-cortisol ratios are obtained in the right and left adrenal veins and the IVC. At the Mayo Clinic, the mean aldosterone/cortisol ratio is 18, but it is accepted because aldosterone/cortisol ratio from the high side to the low side of more than 4 is considered to be diagnostic for unilateral aldosteronoma secretion and less than 3 is consistent with BAH, as shown by this patient (right adrenal vein=0.67, left adrenal vein=1.5; Table).
Currently, adrenal vein sampling remains the gold standard to establish unilateral of primary aldosteronism that can be surgically cured. It is important to understand that CT/MRI imaging may misclassify as many as 37.8% of patients with primary aldosteronism.
Stephanie L. Lee, MD, PhD, is associate professor of medicine; associate chief, section of endocrinology, diabetes and nutrition; and associate professor of medicine at the Boston Medical Center.
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Disclosure: Dr. Lee reports no relevant financial disclosures.