Hepatic Doppler Perfusion Index in Healthy Adults: Standardization, Physiological Reference Limit, and Clinical Perspectives

Background/Objectives: The Doppler perfusion index (DPI) quantifies the ratio of arterial to total hepatic blood flow and reflects hepatic hemodynamic balance. Its clinical applicability is limited by insufficient standardization and the absence of clearly defined physiological reference conditions. This study aimed to establish an upper physiological reference limit for the DPI and to assess its dependence on standardized physiological conditions in healthy adults. Methods: In this prospective study, 44 healthy adults underwent Doppler ultrasonography under standardized conditions (fasting/resting, post-exercise, postprandial). Volumetric blood flow was measured in the portal vein and via the proper hepatic artery and, where feasible, the common hepatic artery. The DPI was calculated as the ratio of arterial to total hepatic inflow. Nonparametric statistical methods were applied. Results: After exclusion of participants with non-standard hepatic arterial anatomy, 39 individuals were analyzed. The DPI varied across physiological conditions, reflecting changes in the relative contributions of arterial and portal venous inflow. Under fasting/resting conditions, values based on the proper hepatic artery showed low variability (mean 0.242 ± 0.057) and normal distribution (Shapiro–Wilk p = 0.625). The empirically derived 90th percentile was 0.30. Measurements based on the common hepatic artery were higher and more variable. Conclusions: The DPI is a physiologically dynamic parameter whose clinical use requires standardized measurement conditions. Under defined protocols, a value of approximately 0.30 may be considered an upper physiological reference limit. Standardization of acquisition and use of the proper hepatic artery enable reproducible and interpretable measurements. This provides a methodological basis for further clinical applications, including oncological contexts in which functional alterations of hepatic perfusion may be relevant.