A 56-year-old woman presented to the author's hospital with microscopic hematuria detected at a medical check-up. Vital signs were normal, and the patient had no symptoms. Laboratory evaluation showed that hemoglobin and serum creatinine levels were 12.1 g/dL and 0.74 mg/dL, respectively. Urine cytology confirmed no evidence of malignancy. Ultrasonography (USG) revealed compression of the left renal vein between the aorta and the superior mesenteric artery, with impaired blood outflow accompanied by distention of the distal portion of the vein (Fig.