4710. Postcontrast CT Liver Attenuation Alone is Superior to the Liver-Spleen Difference for Identifying Moderate Hepatic Steatosis
Authors * Denotes Presenting Author
  1. Alexander Moeller; University of Wisconsin Hospitals and Clinics
  2. Glen Blake; Kings College London
  3. John Garrett; University of Wisconsin Hospitals and Clinics
  4. Ronald Summers; National Institutes of Health
  5. Perry Pickhardt *; University of Wisconsin Hospitals and Clinics
The liver-spleen attenuation difference is often utilized to assess for hepatic steatosis on postcontrast CT, but recent data suggest that liver attenuation alone may be more reliable. We aim to assess the diagnostic performance of postcontrast CT for predicting moderate hepatic steatosis in an older adult cohort undergoing a uniform CT protocol, utilizing hepatic and splenic attenuation values.

Materials and Methods:
A total of 1676 adults (mean age, 68.4 ± 10.2 years; 1045 men, 631 women) underwent a CT urothelial protocol that included unenhanced, portal venous, and 10-minute delayed phases through the liver and spleen. Automated hepatosplenic segmentation for attenuation values (in HU) was performed using a validated deep learning tool. Unenhanced liver attenuation < 40.0 HU, corresponding to 15% MR-PDFF, served as the reference standard for moderate steatosis.

The prevalence of at least moderate steatosis was 12.9% (216/1676). The diagnostic performance of portal venous and delayed liver HU in predicting moderate hepatic steatosis (AUROC = 0.943 and 0.981, respectively) was significantly better than the liver-spleen HU difference (AUROC = 0.814 and 0.912, respectively) (<em>p</em> < 0.001). Portal venous phase liver thresholds of 80 and 90 HU had a sensitivity/specificity for moderate steatosis of 85.6% / 89.6%, and 94.9% / 74.7%, respectively, whereas a liver-spleen difference of -40 and -10 HU had a sensitivity/specificity of 43.5% / 90.0% and 92.1% / 52.5%, respectively. Furthermore, livers with moderate (or severe) steatosis demonstrated significantly less postcontrast enhancement (mean, 35.7 HU vs. 47.3 HU; <em>p</em> < 0.001).

Moderate steatosis can be reliably diagnosed on standard portal venous phase CT using liver attenuation values alone. Consideration of splenic attenuation adds little or no value and can be ignored. Moderate steatosis not only has intrinsically lower precontrast liver attenuation values (<40 HU), but also enhances less, typically resulting in postcontrast liver attenuation values of 80 HU or less.