Introduction

The aim of the study was to establish reference intervals (RI) for ultrasonographically-derived caudal vena cava (CVC) parameters in healthy cats.

Methods

Prospective, observational, experimental single-center study involving 110 cats. Two trained operators scanned cats placed in lateral recumbency, in a randomized order. Two sets of cineloops per cat were recorded by each operator. A blinded observer measured the narrowest inspiratory (CVCinsp) and widest expiratory (CVCexp) CVC diameter over two separate breath cycles for each operator (4 measurements total) at the point the CVC crosses the diaphragm. The CVC collapsibility index (CVC–CI) was calculated. Outliers were identified and removed. A D’agostino-Pearson test was used to assess normality. Reference intervals were calculated according to CLSI guidelines.

Results

Three hundred eighty-four measurements were included for each parameter. CVCinsp and CVCexp were normally distributed; CVC–CI was not. The calculated RIs were 0.7–5.1 mm (90% CI lower limit = 0.5–0.8 mm; upper limit = 4.9–5.2 mm,), 1.9–6.1 mm (90% CI lower limit = 1.8–2.1 mm; upper limit = 5.9–6.2 mm) and 2.8% to 71% (90% CI lower limit =2.0–3.3%; upper limit =64.2–76.5%) for CVCinsp, CVCexp, and CVC–CI, respectively.

Conclusion

Based on this study, the CVC RIs determined from the subxiphoid site in cats appear to be wider than those reported in dogs, particularly for the CVC–CI. Further data analysis is needed to determine inter- and intra-rater variability, and to determine the clinical value of these RIs to identify hyper and hypovolemic cats.

E-mail: t.m.hultman@massey.ac.nz