Delayed computed tomographic characterization of renal masses: preliminaryexperience

Background: To evaluate the performance of delayed contrast enhanced comput ed tomography (DCT) in characterizing renal masses. Methods: Twenty-four patients with suspected renal masses or indeterminate renal masses on previous imaging studies were prospectively evaluated with preintravenous contrast imaging, conventional contrast-enhanced computed to mography (imaging initiated 2 min after intravenous contrast injection), an d DCT (imaging initiated 13 min after injection of intravenous contrast). O nly lesions larger than 1.0 cm were evaluated, with scanning parameters kep t constant across the three scans. Results: All pathologically confirmed renal cell carcinomas (n = 6) were de tected on DCT using a threshold attenuation decrease of 10 Housefield units (HU). A significant decrease (p = 0.031) in attenuation occurred in renal cell carcinomas (mean = 29.6 +/- 23.6 HU) compared with the attenuation cha nge (mean decrease = 1.1 +/- 7.1 HU), which occurred in non-neoplastic rena l cysts (n = 34), Non-neoplastic renal cysts were correctly classified by D CT 32 of 34 times (94%). Conclusions: In this study, DCT distinguished renal cell carcinomas from no n-neoplastic cysts in a vast majority of cases and may aid in characterizin g incidentally discovered renal lesions on postcontrast CT.