Assessment of Liver Function Using Multiphase Hepatic CT: Iodine Uptake and Volumetric Metrics

Overview

This study evaluates the correlation between multiphase hepatic CT parameters—including extracellular volume fraction (ECV), iodine washout rate (IWR), and hepatosplenic volume indices—and liver function measured by indocyanine green retention at 15 minutes (ICG-R15). The findings suggest that these CT-derived metrics may serve as noninvasive indicators of liver dysfunction, potentially complementing or substituting established tests like 99mTc-GSA scintigraphy.

Background

Accurate liver function assessment is critical for managing chronic liver disease, planning hepatectomy, and predicting postoperative outcomes. Traditional static biochemical markers and clinical scores such as the Child–Pugh score have limited predictive value for hepatic decompensation. Dynamic tests like ICG-R15 provide quantitative liver function evaluation but lack morphological imaging data and are time-consuming. Imaging-based methods such as 99mTc-GSA scintigraphy offer regional hepatocyte function assessment but have limitations including cost and availability. Multiphase hepatic CT, routinely used for tumor evaluation, can provide volumetric and iodine uptake parameters that may reflect liver fibrosis and function.

Data Highlights

The study retrospectively analyzed patients with hepatobiliary tumors who underwent multiphase hepatic CT, 99mTc-GSA scintigraphy, and ICG-R15 testing. Exclusion criteria ensured reliable functional and imaging data. ICG-R15 ≥ 20% was used to define severe liver dysfunction. CT parameters assessed included extracellular volume fraction (ECV), iodine washout rate (IWR), and hepatosplenic volume indices. The correlation of these parameters with ICG-R15 and 99mTc-GSA uptake was investigated to evaluate their diagnostic efficacy.

Key Findings

• Multiphase hepatic CT parameters (ECV and IWR) showed significant correlation with liver function measured by ICG-R15.
• Hepatosplenic volumetric indices derived from CT also correlated with liver functional status but had limitations in predicting dysfunction severity.
• ICG-R15 remains a reliable reference standard for liver function assessment, with values ≥ 20% indicating severe dysfunction and contraindication for major hepatectomy.
• 99mTc-GSA scintigraphy provides regional hepatocyte function evaluation but is limited by availability, cost, and radiation exposure.
• CT iodine uptake parameters may offer a noninvasive, readily available alternative to assess liver fibrosis and function during routine imaging.

Clinical Implications

Incorporating multiphase hepatic CT iodine uptake and volumetric metrics into clinical practice could enhance liver function assessment without additional invasive testing. These parameters may aid in preoperative risk stratification and surgical planning, especially when traditional dynamic tests are unavailable or contraindicated. Further validation could establish CT-based metrics as complementary tools alongside ICG-R15 and 99mTc-GSA scintigraphy.

Conclusion

Multiphase hepatic CT-derived iodine uptake and volumetric parameters correlate with established liver function tests and show promise as noninvasive markers of liver dysfunction. They may improve diagnostic accuracy and assist clinical decision-making in patients with chronic liver disease and hepatobiliary tumors.

References

1. Kudo et al. 2021 -- European guidelines on liver function assessment before hepatectomy
2. Makuuchi et al. 1993 -- Indocyanine green retention test for hepatectomy safety
3. Kobayashi et al. 2019 -- 99mTc-GSA scintigraphy in liver function evaluation
4. Saito et al. 2020 -- CT volumetry and liver fibrosis correlation
5. Tanaka et al. 2022 -- Iodine uptake parameters as liver fibrosis markers