j Comput Assist Tomogr, Volume 32, Number 6, November/December 2008
Satomi Kawamoto, MD, Karen M. Horton, MD, and Elliot K. Fishman, MD
Objective: Renal calculi are sometimes incidentally detected on contrast-enhanced computed tomography (CT) scans. The purpose of this study was to evaluate the detectability of renal calculi on arterial phase CT.
Methods: One hundred thirty-three kidneys of 67 consecutive pa¬tients (one had prior unilateral nephrectomy) who underwent mul¬tidetector CT including noncontrast and arterial phase (acquired at 25 seconds from the start of 120 mL of intravenous contrast injec¬tion at a rate of 3 mL/s) scans were retrospectively evaluated. The detectability of renal calculi was determined by comparison of the noncontrast and contrast-enhanced scans.
Results: Sixty-three calculi in 25 kidneys were detected in 17 pa¬tients on noncontrast CT. Forty-seven (75%) of the 63 calculi were also detected on the arterial phase scans. The size and highest atten¬uation of calculi (measured on noncontrast CT) detected on arterial phase scans were 4.3 ± 3.0 mm and 556 ± 353 Hounsfield units, and those detected only on noncontrast CT were 2.8 + 0.8 mm (P = 0.053) and 181 ± 47 Hounsfield units (P < 0.0001), respectively. All calculi larger than 5 mm were detected on arterial phase scans.
Conclusions: On arterial phase scans, 75% of the renal calculi and all renal calculi larger than 5 mm were detected; the attenuation of the calculi had a significant correlation to detectability.