Tomographic Evaluation of the Bronchial and Pulmonary Vascular Relationships in Cats Naturally Infected with Immature Dirofilaria immitis.

Feline heartworm disease (Dirofilaria immitis) often leads to early pulmonary lesions even in infections by immature stages. Diagnosis is challenging due to nonspecific signs and limited sensitivity of serological tests, particularly in immature infections. To evaluate the relationships between the bronchial lumen and the pulmonary vasculature, 38 cats were evaluated thought computed tomography (CT). Of them, 30 were seropositive for D. immitis antibodies with respiratory signs and 8 seronegative controls. Thoracic CT scans were performed, and bronchial and vascular structures were measured. Ratios analyzed included bronchus-to-artery (BA), bronchus-to-vein (BV), and pulmonary vein-to-artery (PV/PA) ratios. Statistical comparisons were conducted across groups and lung lobes. Median BA and BV ratios were significantly higher in seropositive cats across most lung lobes. PV/PA ratios did not differ significantly between groups. Differences across lobes were significant in infected cats for BA and BV ratios. These findings indicate early bronchial remodeling in naturally infected cats, whereas pulmonary arteries and veins were less affected at this stage. Thus, BA and BV ratios are sensitive indicators of early pulmonary involvement and may improve diagnostic accuracy when used alongside conventional serological and imaging tests, which could support early identification and management of feline heartworm disease in endemic regions.