We herein report the case of a patient with a juxtaglomerular cell tumor (JCT). Dynamic enhanced computed tomography revealed a small nodule on the surface of the lower pole of the right kidney. Selective renal venous sampling showed an elevated level of plasma renin activity (PRA) in the right lower pole renal vein only. We performed right partial nephrectomy and diagnosed the patient with JCT. Making a diagnosis of JCT is often difficult due to the small size of the tumor and the lack of

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... nd the lack of lateralization of the PRA on renal venous sampling. This case highlights the importance of performing selective renal venous sampling for the preoperative diagnosis of JCT. A 34-year-old woman with a family history of hypertension was referred to our hospital for a further examination of persistent hypertension lasting for over 17 years. At 18 years of age, although hypertension (180/120 mmHg) was first noted during an examination for headaches, the patient did not receive any diagnostic examinations or treatment. At 24 years of age, hypertension was again noted during an examination for urinary tract stones. At that time, a diagnostic examination to assess the hypertension was performed. The endocrine examination revealed that the PRA level was elevated (19 ng/mL/hr; normal level, 0.2-2.7 ng/mL/hr); however, the plasma aldosterone concentration (PAC) was normal (130 pg/mL; normal level, 36-240 pg/mL). Nonenhanced CT and MRI of the abdomen showed no abnormal findings, and magnetic resonance angiography (MRA) and Doppler ultrasonography demonstrated no evidence of renal