Clear Cell Renal Cell Carcinoma Metastases Visibility: Split-Bolus Single Scan vs. Portal Venous Phase CT

Objective To assess the impact of split-bolus (SB) single scan CT on the conspicuity of clear cell renal cell carcinoma (ccRCC) metastases compared to single-bolus injection. Methods This retrospective cohort study included consecutive patients with histologically proven metastatic ccRCC who underwent both SB and single-bolus portal venous abdominal CT within 6 months between 2017 and 2022 in a single tertiary center. SB CT utilized BMI-adjusted contrast dose and kVp (80-120) with concurrent arterial and portal venous phases. Single bolus CT utilized BMI-adjusted contrast dose at 120kVp at the portal venous phase. Wilcoxon rank test compared the conspicuity of metastases between the protocols. Results Of the 47 patients, 80.9% were male, with a mean age of 67 ± 10.4 years and a BMI of 27.1 ± 5.7. There were 48 paired CTs performed with a median interval of 93 days. Contrast dose was 143 ± 27 cc for SB and 108 ± 26 cc for single-bolus ( p < 0.001). 66 metastases were analyzed, with an average size of 2 cm: 48.5% in the pancreas, 28.8% in skeletal muscle, and 22.7% in the liver. The median contrast-to-noise ratio (CNR) was higher with SB compared to single-bolus for all metastases (3.0 vs. 1.4), pancreatic metastases (2.7 vs. 1.4), muscle metastases (5.2 vs. 2.0), and liver metastases (2.8 vs. 0.9), all p < 0.001. Conclusions SB scan provides dramatically higher conspicuity of ccRCC metastases as compared to single-bolus portal venous CT.