Retinal vascular calibers and correlations with biomarkers in bitches with pyometra-induced systemic inflammatory response syndrome.

Abstract

Background and aim: Pyometra is a common uterine disease in intact bitches, frequently progressing to systemic inflammatory response syndrome (SIRS). While retinal vascular alterations have been observed in human SIRS cases, similar evaluations are lacking in veterinary medicine. This study aimed to evaluate retinal vascular calibers in bitches with pyometra-induced SIRS (P-SIRS) and explore correlations between retinal measurements and hematological, biochemical, vascular endothelial growth factor (VEGF), and interleukin-4 (IL-4) levels.

Materials and methods: A prospective observational study was conducted on 40 bitches diagnosed with P-SIRS and 30 clinically healthy controls. Retinal images were captured at admission using a smartphone coupled with a Volk iNView® (Volk®, Mentor, OH, USA) device. Retinal arteriolar and venular calibers within 0.5-1 disk diameter from the optic disk were measured using ImageJ software (https://imagej.net/ij/index.html). Concurrent hematology, serum biochemistry, VEGF, and IL-4 levels were analyzed. Statistical comparisons and correlations were assessed using non-parametric tests and Spearman's correlation.

Results: Retinal arteriolar calibers were significantly narrower (p = 0.0001) and venular calibers significantly wider (p = 0.0068) in P-SIRS patients compared to controls. Serum VEGF and IL-4 concentrations were markedly elevated in the P-SIRS group (p < 0.05). Retinal venular calibers positively correlated with band neutrophils (p = 0.02), monocytes (p = 0.04), and negatively with albumin (p = 0.008). Retinal arteriolar calibers negatively correlated with segmented neutrophils (p = 0.04) and VEGF (p = 0.0003). No ophthalmoscopically visible retinal lesions were detected.

Conclusion: Bitches with pyometra-induced SIRS exhibited significant retinal microvascular alterations characterized by arteriolar narrowing and venular dilation. These vascular changes correlated with systemic inflammatory markers and VEGF levels, suggesting that retinal vascular assessment may serve as a non-invasive biomarker for systemic inflammation in veterinary patients. Despite microvascular changes, no clinically visible retinal lesions were observed, warranting further longitudinal studies to elucidate their prognostic significance.