Evaluation of vena cava caudalis diameter in cats brought to theemergency room and its importance in prognosis

This thesis study was conducted to evaluate the intravascular volume status in cats presented to the Emergency Clinic of Selçuk University Animal Hospital with various health problems. In addition to clinical findings, the diameter of the caudal vena cava was measured before and after fluid replacement for stabilization, and the collapsibility (caval) index was calculated. In humans and other animal species, a reduction in the diameter of the caudal vena cava generally indicates hypovolemia, whereas an increase suggests hypervolemia. The collapsibility index provides valuable information in the assessment of fluid responsiveness. This study was conducted on a total of 50 client-owned cats (n=50) presented to the Emergency Clinic of Selçuk University Animal Hospital with various health problems, and 20 healthy cats (n=20) presented to the Internal Medicine Clinic for routine health examinations or vaccinations. In the decision-making process for fluid therapy aimed at patient stabilization, anamnesis, physical examination, and laboratory findings were evaluated in conjunction with ultrasonographic measurements of the caudal vena cava diameter. Subsequently, the collapsibility index was calculated. Statistically significant changes were observed in certain clinical and laboratory parameters when data from the diseased cats—both before (pre-fluid replacement, PFR) and after (post-fluid replacement, PoFR) fluid therapy for stabilization—were compared with those of the healthy control group. In the patient group, parameters such as age, body temperature, capillary refill time (CRT), skin turgor, pH, pCO₂, HCO₃⁻, base excess (BE), ionized calcium (Ca) concentration, hemoglobin (HGB) concentration, maximum and minimum diameters of the caudal vena cava (CVCmax and CVCmin) measured during expiration and inspiration, and the caval index (CI) showed statistically significant differences compared to the healthy control group (p < 0.05). Additionally, when pre- and post-fluid replacement values within the patient group were compared, significant improvements were observed in skin turgor, pH, pCO₂, HCO₃⁻, base excess (BE), lactate concentration, CVCmax, and CVCmin values following fluid therapy (p < 0.05). The caval index was significantly higher in the pre-fluid replacement period compared to the healthy group (p < 0.05); however, the change in caval index before and after fluid replacement was not statistically significant (p > 0.05). In conclusion, alongside routine physical clinical examinations, ultrasonographic measurement of the caudal vena cava diameter and calculation of the caval index may be useful in estimating intravascular volume and monitoring fluid therapy in both healthy and diseased cats. However, considering the small size and sensitivity of cats, we believe that certain technical challenges related to the use of ultrasonography and difficulties in interpreting the results may still exist.