Introduction: Blood flow of liver with dual supply from the portal vein and the hepatic artery is very unique among other parenchymal organs. Doppler ultrasonography (US) is the most feasible, easiest, non-invasive method for hepatic artery screening after liver transplantation (LT). The morphologic and hemodynamic assessment of the hepatic artery posttransplantation is enabled by using Doppler US. However, due to the complex hemodynamics of the liver and vascular complications after LT, it becomes a challenge to screen the hepatic artery properly. The aim of this study is to assess the efficacy of fasting on Doppler US screening of the hepatic artery relying on changes in splanchnic circulation.
Materials and Methods: Liver transplant follow-up patients who admitted to the general surgery transplantation clinic were prospectively referred to radiology department, from September 2017 to October 2017. All the patients were evaluated twice with Doppler ultrasonography, first with a minimum fasting period of 8 hours and 30 minutes after a standard meal of 15 grams of chocolate. Patients with diabetes, vascular thrombosis or stenosis of either hepatic artery or portal vein, and pediatric patients were excluded. Diameter of the hepatic artery, hepatic arterial peak systolic velocity (HAV, cm/s), hepatic arterial blood flow (HABF, L/min), hepatic arterial resistive index (HARI) and portal vein peak velocity (PVV, cm/s) were documented before and after the meal.
Results: The mean HABF of 19 patients was found 0.244 L/min after fasting and 0.118 L/min after meal. The mean postprandial HARI was increased from 0.66 to 0.71. The mean hepatic arterial diameter and HAV were observed to decrease after meal, respectively from 4.2 mm to 3.2 mm and from 110 cm/s to 86 cm/s. On the other hand, mean postprandial PVV was increased  from 49 cm/s to 54 cm/s (p<.05).
Conclusion: The prandial effect on hepatic artery in patients with LT is similar to that of healthy patients, where HABF decreases and HARI increases after meal. Compared to hepatic arterial diameter, velocity and RI, hemodynamic flow changes in hepatic artery is more likely to be affected by meal intake. To the best of our knowledge, this effect has not been studied in transplanted livers in English literature so far. This study shows that due to excess splanchnic circulation after meal, it is more difficult to evaluate hepatic artery of a transplanted liver sonographically. Therefore, in cases where imaging hepatic artery by Doppler US becomes unsuccessful, the examination should be repeated after a fasting period of minimum 8 hours.