Veterinary surgery : VS1998; 27(3); 175-181; doi: 10.1111/j.1532-950x.1998.tb00116.x

Transendoscopic chemical ablation of progressive ethmoidal hematomas in standing horses.

Abstract: To examine the response of horses with progressive ethmoidal hematoma (PEH) to intralesional injection of 4% formaldehyde solution. Methods: Nasal passages of horses affected with PEH were examined endoscopically at different intervals to determine the effects of intralesional injection of formaldehyde solution. Methods: 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. Conclusions: Ablation of PEH using formaldehyde solution avoids general anesthesia and problems associated with ablation by conventional surgery or laser.
Publication Date: 1998-05-30 PubMed ID: 9605229DOI: 10.1111/j.1532-950x.1998.tb00116.xGoogle Scholar: Lookup
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This research study tests the effectiveness of 4% formaldehyde solution injected directly into progressive ethmoidal hematomas (PEH) in horses, as a potential alternative to surgical or laser-based treatments.


  • The research concentrated on the usage of 4% formaldehyde solution for the treatment of a progressive condition seen in horses known as Progressive Ethmoidal Hematomas (PEH).
  • A total of 21 horses with PEH underwent the procedure in this research. Horses were treated while awake (standing) to avoid the need for general anesthesia.
  • PEH was injected transendoscopically, a procedure involving the placement of an endoscope and needle system into the nasal passage via the nostril to the site of the hematoma to deliver the formaldehyde solution.
  • The horses were monitored over a specific time period and were retreated at different intervals until the PEH was fully gone or was so small that additional injection was no longer possible.


  • The study results showed that the size of the lesions diminished significantly or were fully gone after 1 to 18 injections. The median number of injections required was 5, with an average of around 7 injections.
  • Results showed that 17 out of the 28 total lesions treated (approximately 60.7%) fully resolved after 1 to 18 injections.
  • Five of the lesions showed a marked decrease in size but did not completely resolve even after 1 to 18 injections. Treatments were discontinued in these cases after a certain period ranging between 4.0 to 25.1 months from the first injection.
  • In one case, after an injection, the horse’s PEH had to be surgically removed. Three horses, including one horse with PEH in both nasal passages, were lost to follow-up.
  • One horse developed signs of laminitis, a serious disease in horses that affects their feet. However, no other complications were observed in the study.


  • The study concluded that a transendoscopic injection of 4% formaldehyde solution could effectively treat horses with PEH.
  • Additionally, the approach provided the advantage of avoiding general anesthesia and potential complications associated with conventional surgical or laser ablation techniques for treatment of PEH.

Cite This Article

Schumacher J, Yarbrough T, Pascoe J, Woods P, Meagher D, Honnas C. (1998). Transendoscopic chemical ablation of progressive ethmoidal hematomas in standing horses. Vet Surg, 27(3), 175-181.


ISSN: 0161-3499
NlmUniqueID: 8113214
Country: United States
Language: English
Volume: 27
Issue: 3
Pages: 175-181

Researcher Affiliations

Schumacher, J
  • Department of Large Animal Medicine and Surgery, Texas Veterinary Medical Center, College of Veterinary Medicine, College Station, USA.
Yarbrough, T
    Pascoe, J
      Woods, P
        Meagher, D
          Honnas, C

            MeSH Terms

            • Animals
            • Endoscopy / veterinary
            • Ethmoid Sinus
            • Female
            • Formaldehyde / administration & dosage
            • Formaldehyde / therapeutic use
            • Hematoma / therapy
            • Hematoma / veterinary
            • Horse Diseases / therapy
            • Horses
            • Injections, Intralesional / veterinary
            • Male
            • Paranasal Sinus Diseases / therapy
            • Paranasal Sinus Diseases / veterinary
            • Solutions
            • Treatment Outcome


            This article has been cited 2 times.
            1. Burbery K, Simon O, Woolford L, Ferlini Agne G. Bilateral thyroid adenomas in an alpaca.. J Vet Intern Med 2021 Nov;35(6):2937-2942.
              doi: 10.1111/jvim.16285pubmed: 34626440google scholar: lookup
            2. Conti MB, Marchesi MC, Rueca F, Puccetti M. Diagnosis and treatment of progressive ethmoidal haematoma (PEH) in horses.. Vet Res Commun 2003 Sep;27 Suppl 1:739-43.