Tomographic evaluation of the bronchial and pulmonary vascular relationships in cats naturally infected of heartworm

Abstract

Feline dirofilariosis mainly differs to canine dirofilariosis because of the great response of the animal against the worm infection (Dirofilaria immitis), producing an intense lung inflammatory reaction, developing what is known as “Heartworm Associated Respiratory Disease” (HARD). This inflammation can alter the vasculature and bronchial structure of the lung. Computed tomography (CT) is increasingly present in veterinary medicine, being helpful in the diagnosis of feline thorax pathologies. The measurement of the bronchial lumen to pulmonary artery (BA), bronchial lumen to pulmonary vein (BV) and pulmonary vein to pulmonary artery (PV/PA) ratios are of great relevance to recognise changes in the different pulmonary structures. The aim of this study was to analyse these ratios in cats naturally infected with D. immitis in order to evaluate the damages this disease generates in this species. Considering the age, breed and sex data, 24 animals were analysed to assess the BA, BV and PV/PA measurements with CT scan, differentiating between animals diagnosed with HARD (18) and healthy animals (6). Significant changes were not observed in the diameter of the arteries of infected cats, thus not showing signs of pulmonary hypertension. Contrarily, bronchi were affected, so the BA ratio could be used to determine those altered in cats with bronchiectasis due to respiratory pathologies. The BV ratio has not been previously described in cats, so these results could serve as reference values for future investigations. Furthermore, it was observed that 4 lung lobes were affected, so this ratio could also be useful to detect bronchial lumen alterations. The PV/PA ratio did not show significant differences for any of the lung lobes between the studied groups, since neither the artery nor the vein were affected by the disease. Therewith, BA and BV ratios could be of usefulness when the bronchial structure is altered by HARD, and might be practical in the diagnosis of the disease in endemic areas. Even so, more studies should be carried out to support these results.