Assessment of Hepatic Function and Parenchyma Attenuation with Indocyanine Green, Ultrasound and CT in a Rat Model: Preliminary Standardization of Baseline Parameters

Abstract

Purpose: Standardization in experimental animal models plays a crucial role in preclinical studies by providing useful information on the type and extent of liver disease. However, it is necessary to combine these determinations with functional dynamics imaging and testing techniques to implement a non-invasive protocol for liver evaluation. Method: Six healthy SD rats were followed for 4 weeks. The aim was to determine hepatic function, perfusion and parenchyma attenuation with biochemical blood parameters, indocyanine green, ultrasound and computed tomography. Results: Indocyanine green clearance 5 and 10 minutes after its injection was 80.12% and 96.59%, respectively. Hepatic perfusion evaluation with the high-frequency ultrasound was related to cardiovascular hemodynamic and renal perfusion. Portal area, hepatic artery resistance index and average between hepatic artery and porta was 3.41 ± 0.62 mm 2 , 0.57 ± 0.04 mm 2 /s and 4.82 ± 0.96 mm 2 /s, respectively. Heart rate, cardiac output, left renal artery diammetre and renal blood flow were 331.01 ± 22.22 bpm, 75.58 ± 8.72 mL/min, 0.88 ± 0.04 mm 2 and 13.65 ± 1.95 mm 2 /s. CT-scan hepatic average volume for each rat were 21.08±3.32, 17.57±2.76, 14.87±2.83 and 13.67±2.45 cm 3 with an average attenuation coefficient of 113.51±18.08, 129,19±7.18, 141,47±1.95 y 151,67±1.2 HU. Conclusion: Indocyanine green and high-frequency ultrasound could be used in rats as a suitable marker of liver function. Computed tomography help to characterize liver parenchyma, and could be a potential tool for early detection and linear follow-up of patients. Further studies in rats with liver disease are necessary to verify the usefulness of these parameters.Table 1Indocyanine Green plasma clearance (ICG) rateICG plasma concentration (μg/mL)Min 1Min 5Min 10Rat 1128.1±55.61819.45±2.285.41±3.32Rat 2161.47±65.8228.58±9.235.75±3.60Rat 3160.63±27.6833.14±6.957.44±0.52Rat 4189.16±51.0538.13±2.863.47±0.05Rat 5165.91±23.9147.51±8.822.90±0.76Rat 6130.65±10.2119.24±3.546.91±0.99Average ICG Concentration (μg/mL)155.99±23.1131.01±11.015.31±1.82Average Clearance %0.0080.1296.59 Open table in a new tab μg/mL: microgram/mililitre