選択的腎静脈サンプリングが陰性であった思春期男子のレニノーマ：症例報告と文献レビュー

Juxtaglomerular cell tumor (reninoma) is a rare benign renal neoplasm causing secondary hypertension via autonomous renin over-secretion, which is extremely rare in children and adolescents. Here we report a 13-year-old boy with a two-year misdiagnosis of resistant hypokalemic hypertension, who underwent unnecessary left adrenalectomy based on ambiguous adrenal computed tomography (CT). Biochemical tests revealed hyperreninemic hyperaldosteronism with normal aldosterone-to-renin ratio. Renal artery CT identified a tiny low-density lesion in the upper pole of the left kidney, while contrast-enhanced ultrasound (CEUS) clearly displayed characteristic hypoperfusion of the mass. Selective renal vein sampling (SRVS) failed to demonstrate a lateralized renin gradient, a finding consistent with the known low sensitivity of this test for small juxtaglomerular cell tumors (JGCT). Laparoscopic nephron-sparing tumorectomy was performed, and histopathological and clinical features together supported the diagnosis of reninoma. Blood pressure and serum electrolytes normalized postoperatively without antihypertensive or potassium supplementation, with complete quantitative biochemical and imaging surveillance confirming stable remission over the 3-year follow-up. This case highlights that CEUS acts as a radiation-free auxiliary localization modality for suspected pediatric reninoma and provides complementary functional information when SRVS yields false-negative results; definitive diagnosis requires integrated assessment of clinical manifestations, biochemical markers, multimodal imaging, and pathological findings rather than relying on a single imaging technique. Clinicians should raise vigilance of reninoma in children with refractory hypokalemic hypertension to avoid misdiagnosis and unnecessary adrenal surgery.