Sonography is useful for evaluating feline splenic pathology. Normal feline sonographic splenic measurements are not well characterized. Unlike the dog and Cheetah, sonographic response of the feline spleen to drugs and hemorrhage has not been established. The study aims included; evaluating normal splenic sonographic size, assessing the effect of sevoflurane and non-splenic hemorrhage on the sonographic appearance and size of the feline spleen, and correlating splenic findings with packed cell volume (PCV), total protein (TP), and regenerative response, as indicated by a complete blood count (CBC).
Sixty healthy blood donor cats were enrolled in the study. Sevoflurane was used for anesthetic induction and maintenance. Transverse images of the splenic mid body (13 MHz) were made and splenic sonographic measurements (height, width and cross sectional area [CSA]), echogenicity relative to the left renal cortex and echotexture were recorded at four time periods. Sonographic evaluation was performed at baseline prior to anesthesia and blood donation, following anesthesia induction, following completion of blood donation while under anesthesia, and 7-10 days after blood donation. PCV, TP, and CBCs were obtained prior to blood donation and 7-10 days following blood donation, with PCV and TP evaluated in eight cats immediately following blood donation.
Height, width, CSA, PCV and TP were compared across time periods using linear mixed effects models. The models included period as the primary factor, with additional covariates such as age, gender, and total blood donated. Differences in CBC values between days were assessed using the Wilcoxon Rank Sum test. Holm’s method was applied to adjust for multiplicity and control the overall Type 1 error rate at α=0.05.
In these clinically normal cats, the means ± standard deviation for transverse splenic size at baseline were: height 8.2 ± 1.4 mm, width 26.7 ± 4.4 mm, and CSA 1.6 ± 0.5 cm2. The spleen was diffusely homogenous and subjectively isoechoic or mildly hyperechoic relative to the left renal cortex. Height significantly increased from baseline after anesthetic induction, with a decrease in size at the post-blood donation period. Width was significantly decreased at recheck compared with post anesthetic and post-blood donation periods for castrated male cats. CSA was significantly increased from baseline for castrated male cats after anesthetic induction and post-blood donation. Width or CSA were not significantly different at any time period for spayed female cats. PCV and TP were significantly reduced immediately following blood donation and TP was significantly increased at recheck. Reticulocytes, mean corpuscular volume and red cell distribution width were all significantly increased at recheck, with a significant decrease in hemoglobin concentration at the same time period.
Normal sonographic splenic measurements and appearance in healthy cats are reported. While there were statistically significant changes in splenic height, width, and CSA after sevoflurane anesthesia and/or blood collection, these changes were of low magnitude and likely not clinically relevant. Sevoflurane anesthesia and blood donation did not alter the subjective echogenicity and echotexture. A regenerative bone marrow response was present in all cats, and normal PCV was reached 7-10 days following moderate non-splenic hemorrhage.