Hypertension and hypokalemia in a 15-year-old boy: answer

Excerpt

During any evaluation of patients with hypertension and hypokalemic metabolic alkalosis, hormones, including plasma renin activity (PRA), serum aldosterone, and serum cortisol concentration, should be checked [1]. The results of these hormone analyses can indicate the specific area requiring a more specific evaluation. We therefore assessed PRA and aldosterone level once again after all of the antihypertensive drugs had been withdrawn. We found PRA and alderstone levels of 44.8 ng/ml/h (normal range: 0.5–1.9 ng/ml/h) and 140 ng/dl (normal range: 0.8–17.2 ng/dl), respectively, when the patient was in the supine position. These results allowed us to rule out true mineralocorticoid excess, such as primary aldosteronism or glucocorticoid-remediable aldosteronism. We also ruled out non-aldosterone mineralocorticoid excess, which is observed in patients with congenital adrenal hyperplasia or in apparent mineralocorticoid excess, because the suppression of both PRA and serum aldosterone concentration is expected in these diseases [1]. The results steered us towards a diagnosis of secondary aldosteronism with excess renin secretion, a condition that can occur in renal parenchymal disease associated with inflammation or scarring, renovascular diseases, or aortic coarctation [2]. However, our previous clinical, laboratory, and radiological findings did not indicate any of these diseases. Our plan, therefore, was to repeat the renal ultrasound and renal arterial Doppler ultrasound and, if the results were normal, to perform a conventional angiography. Renal ultrasound revealed a 3-cm, solid, exophytic mass in the upper pole of the left kidney. The mass was isoechoic to the renal parenchyma, and it could not be demarcated from the parenchyma other than by the bulging of the renal contour. Magnetic resonance imaging (MRI) of the abdomen showed a 3.5-cm well-circumscribed mass in the posterolateral upper pole of the left kidney. The lesion was slightly heterogenous and isointense to the renal medulla on both T1- and T2-weighted images (Fig. 1). Dynamic contrast-enhanced imaging revealed rapid enhancement in the early arterial phase, which subsequently became isointense with the surrounding normal parenchyma in the delayed phase. While these evaluations were being carried out, the hypertension of the patient once again became apparent, and antihypertensive therapy was restarted. The patient was transferred to the Department of Pediatric Urology for excision of the lesion, and the mass was subsequently removed by nephron-sparing surgery. Gross examination of the specimen demonstrated a well-encapsulated, cortically based lesion measuring 3 cm in diameter. The cut surface was gray-white in color, and hemorrhagic areas were identified. Histologically, the tumor was composed of a uniform population of round to polyhedral cells with granular cytoplasm. The nuclei were generally round to oval and hyperchromatic. Vascular structures were prominent. Immunhistochemical analysis revealed that the tumor cells were positive for vimentin, CD34, smooth muscle actin, and CD31. These cells were nonreactive for PanCK. The pathological diagnosis was compatible with a juxtaglomerular cell tumor (reninoma) (Fig. 2). One week after tumor resection, the results of the laboratory tests were as follows: Na, 139 mEq/L; K, 4 mEq/l; pH, 7.37; pCO₂, 37 mmHg; HCO₃, 21 mEq/l; base excess, −3.3; PRA, 1.2 ng/ml/h (normal range: 0.5–1.9 ng/ml/h); aldosterone, 31 ng/dl (normal range: 0.8–17.2 ng/dl). The ambulatory blood pressure monitoring was completely normal without any antihypertensive agent.

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