Evaluation of caudal vena cava size using computed tomography in dogs under general anesthesia

This study investigated the association between caudal vena cava (CVC) size and circulatory dynamics in dogs using computed tomography (CT) under general anesthesia. The subjects were 104 dogs who had undergone CT under general anesthesia in the past. The ratio of short diameter of the CVC to aortic diameter (CVC_S/Ao) and the ratio of long to short diameter of the CVC (CVC_L/CVC_S) in the thorax and abdomen, respectively, were calculated using factors such as mean blood pressure (MBP), shock index (SI), anemia, hypoproteinemia, presence of intra-abdominal mass, and cardiac disease. There was a significant but negligible negative correlation between CVC_S/Ao and MBP. In contrast, no significant correlation was found between CVC size and SI. The low MBP group had significantly higher CVC_S/Ao of the thorax than the normal MBP group. The group with intra-abdominal mass had significantly lower CVC_S/Ao of the abdomen than the group without intra-abdominal mass. The group with cardiac disease had significantly lower CVC_L/CVC_S of the thorax than the group without cardiac disease. In multiple regression analysis, low MBP, cardiac disease, intra-abdominal mass, and anemia were significant factors for CVC_S/Ao of the thorax, CVC_L/CVC_S of the thorax, CVC_S/Ao of the abdomen, and CVC_L/CVC_S of the abdomen, respectively. In conclusion, CVC size assessment using CT in dogs under general anesthesia is influenced by various factors.