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    Canine Chemodectoma

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    What Is A Chemodectoma?

    Chemodectoma is a relatively rare, usually benign (non-cancerous) tumor originating in chemoreceptor tissue. Also called an aortic-body tumor, carotid-body tumor, glomus jugulare tumor, Nonchromaffin Paraganglioma. It has been reported in a variety of domestic animals, but the neoplasm appears to develop most commonly in dogs. Although rare, chemodectoma is the second most common cardiac tumor after hemangiosarcoma.

    Aetiology

    The cause of chemodectomas is uncertain. However, the predisposition might be aggravated by chronic hypoxia in brachycephalic breeds of dogs.

    Susceptible Dog Breeds

    Dogs of bulldog ancestry:

    are at higher risk of developing chemodectomas. These tumors occur more commonly in males than in females.

    Function Of The “Bodies”

    Aortic bodies are located, as their name would suggest, in the aortic arch. The carotid bodies are closely related chemoreceptor organs, in terms of origin and function, that are located at the bifurcation of the common carotid artery. Together, these chemoreceptor organs monitor the partial pressures of oxygen and carbon dioxide (PO2 and PCO2, respectively) and hydrogen ion concentration, or acidity (pH), of arterial blood and have input to the midbrain for the regulation of respiration and circulation.

    Chemodectoma can develop from the aortic body at the base of the heart between the aorta and pulmonary artery, between the aorta and right atrium, between the pulmonary artery and left atrium, or from the carotid body in the neck. Aortic body chemodectoma account of nearly 80% of all chemodectomas in dogs.

    Tumor Growth

    Tumors of the cardiac base usually develop in older animals. A breed particularly predisposed to such tumors involves boxers. The manifestation of tumors of this type in boxers may be linked to the type of structure in the upper respiratory tract (brachycephalicairway syndrome -BAS).

    The primary features of BAS include stenotic nares, an elongated soft palate, and distortion of the pharyngeal soft tissues due to shortening of the skull. These abnormalities are seen in brachycephalic breeds, and they increase resistance to airflow in the upper respiratory tract. The increased negative pressure required during inspiration may result in changes, including laryngeal collapse. These abnormalities cause chronic hypoxia and are suspected of providing a cause of abnormal growth and, finally, tumor of chemoreceptor cells.2

    Unless these tumors are of sufficient size to cause impairment of the heart and large vessels, they often go unnoticed, and frequently they are found during routine clinical examination due to other diseases.

    Diagnosis

    Diagnosis and treatment of cardiac tumors continue to be difficult. The diagnosis takes advantage of the most modern imaging techniques, i.e., ultrasonography, radiography and magnetic resonance.

    Treatment

    Surgical removal aortic body chemodectoma is possible depending on the size, location and the degree of its spread to other tissues. However, many animals benefit from pericardiectomy (surgical removal of part or most of the pericardium) without surgical removal of the tumor.3

    References:

    1. Harm et al. – Investigating The Sudden Death Of A Dog – Can Vet J. 2010 Feb; 51(2): 210–212. PMCID: PMC2808292
    2. Noszczyk-Nowak et al. – Case Study Cases With Manifestation Of Chemodectoma Diagnosed In Dogs – Acta Veterinaria Scandinavica 2010, 52:35
    3. Theresa Welch Fossum – Small Animal Surgery Textbook

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