Transendoscopic Chemical Ablation of Progressive Ethmoidal Hematomas in Standing Horses

OBJECTIVE: To examine the response of horses with progressive ethmoidal hematoma (PEH) to intralesional injection of 4% formaldehyde solution. STUDY DESIGN: Nasal passages of horses affected with PEH were examined endoscopically at different intervals to determine the effects of intralesional injection of formaldehyde solution. ANIMALS: 21 horses with PEH. METHODS: PEHs were injected transendoscopically with 4% formaldehyde solution. Horses were examined endoscopically and retreated at different intervals until the PEH was eliminated or was so small that reinjection was not possible. RESULTS: Lesions diminished significantly in size or were eliminated after 1 to 18 injections (median, 5; mean, 7.0 +/- 5.62). Seventeen lesions (60.7%) resolved completely after 1 to 18 injections (median, 5; mean, 7.2 +/- 5.71). Five lesions decreased markedly in size but did not resolve after receiving 1 to 18 injections (median, 5; mean, 7.6 +/- 6.66). Injection of these lesions was discontinued 4.0 to 25.1 months (median, 9.5; mean, 11.02 +/- 8.446) after the first injection. The PEH of one horse was removed surgically after one injection. Three horses, one with bilateral PEH, were lost to follow-up. One horse developed signs of laminitis. No other complications were observed. CONCLUSIONS: Horses with a PEH can be treated effectively by transendoscopic, intralesional injection of 4% formaldehyde solution. CLINICAL RELEVANCE: Ablation of PEH using formaldehyde solution avoids general anesthesia and problems associated with ablation by conventional surgery or laser.