Pseudoenhancement is an artifact in postcontrast CT evaluation of renal cysts.
A renal cystic lesion is considered "enhancing" when there is at least a 20 HU increase in attenuation from the precontrast series to the postcontrast series. An increase in attenuation of 10-20 HU is considered indeterminate.
Caution must be exercised, however, when using this criteria in small (<1 cm) intraparenchymal renal cystic lesions. These small lesions may actually be water attenuation (<10 HU), but because of the intense enhancement of the surrounding renal parenchyma, the Hounsfield unit reconstruction algorithm may artificially increase the attenuation in the benign cyst, making it appear as a possibly malignant enhancing cystic lesion.
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