ABSTRACT
BACKGROUND: Echocardiographic indices of the inferior vena cava have been associated with elevated right atrial pressures in humans. HYPOTHESIS/OBJECTIVES: Describe caudal vena caval (CVC) sonographic dimensions in healthy cats compared to cats with cardiogenic cavitary effusion (CCE), cardiogenic pulmonary edema (CPE), or non-cardiac causes of cavitary effusion (NCE). ANIMALS: 30 healthy control cats and 52 client-owned cats with CCE, CPE, or NCE examined at two university hospitals. METHODS: Sagittal 2-dimensional (2D) and M-mode CVC dimensions were acquired from the subxiphoid view. Caudal vena cava collapsibility index (CVC-CI) was calculated. Variables were compared between study groups using Kruskal-Wallis and Dunn's Bonferroni testing. Receiver operating characteristic curves were used to assess sensitivity and specificity for diagnostic categories. RESULTS: Healthy cats had sagittal 2D and M-mode (median, interquartile range) CVC maximal dimensions of 2.4 mm (1.3-4.0) and 3.4 mm (1.5-4.9) and CVC-CI of 52% (45.2-61.8) and 55% (47.8-61.3), respectively. The CVC maximal dimensions in healthy controls were smaller than in cats with cavitary effusions or pulmonary edema (all P<0.05). CVC-CI was different between CCE and NCE (P<0.0001) with cutoffs of CVC-CI ≤38% (2D) or ≤29% (M-mode) being 90.5% and 85.7% sensitive, and 94.4% and 100% specific for diagnosis of CCE, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: Caudal vena cava measurements are larger in cats with cavitary effusions and cats with CPE than healthy cats. In cats with cavitary effusion, decreased CVC-CI, ≤38% (2D) or ≤29% (M-mode), was helpful in distinguishing between cardiogenic and noncardiogenic etiology.