An 84-year-old man presented at our hospital with complaints of severe gross hematuria and lower right abdominal pain. A right renal mass was detected by ultrasound sonography and plain computerized tomography (CT) scan, but an exact diagnosis was not obtained. Because the patient presented with moderate renal dysfunction and severe gross hematuria, we were unable to perform imaging studies using contrast material or ureteroscopic instruments. Finally, mercaptoacetylglycyl-glycylglycine (MAG3) scintigraphy and magnetic resonance imaging (MRI) demonstrated renal cell carcinoma, and we performed transarterial embolization (TAE) therapy using ethanol and gel foam. Based on their efficacy and noninvasiveness, we conclude that MAG3 scintigraphy and MRI are the optimal modalities for imaging in patients with renal dysfunction.