Increase in CT attenuation values of parapelvic renal cysts after retrograde pyelography

The differentiation of high-density parapelvic renal cysts from other renal masses by computerized tomography is reported. In this case, the high density renal cyst was seen after retrograde pyelography in which the contrast material artifactually raised the attenuation value temporarily. A repeat CT examination after a short delay can be diagnostic. (KRM)