SEVERE LAMENESS CAUSED BY METASTATIC RENAL ADENOCARCINOMA
OF THE THIRD PHALANX IN A WARMBLOOD MARE
Oosterlinck M.1, Verbraecken S.1,2, Maes S.³, Gielen I.², Raes E.²
Departments of Surgery and Anaesthesiology1, Medical Imaging² and Pathology³, Faculty of
Veterinary Medicine, Ghent University, Merelbeke, Belgium. E-mail:
maarten.oosterlinck@ugent.be
Introduction
Equine musculoskeletal neoplasia and osseous metastasis of a soft tissue tumour are very rare.
Objective
To describe the clinical and imaging findings in a warmblood mare with a primary renal
adenocarcinoma and metastases to the lungs, the myocardium, along the perirenal lymphatic
tract and to the third phalanx, characterized by progressive unilateral forelimb lameness.
Materials and Methods
An 19-year-old warmblood mare (515 kg) in a poor body condition and with a chronic history
of hematuria presumably attributable to renal neoplasia, was referred with acute, progressive,
unilateral forelimb lameness with marked pulsation and metacarpal oedema. The presumptive
diagnosis of a hoof abscess could not be confirmed after thorough inspection of the hoof. An
abaxial sesamoid block was positive. Radiographic examination revealed a well-defined
expansile osteolytic area of approximately 4 cm in diameter, involving the dorsomedial half
of the third phalanx and extending into the subchondral bone. The dorsomedial side of the
hoof wall was rasped until dermal tissue was exposed. These laminae showed a dark red
appearance with remarkably poor bleeding. Given the history of renal neoplasia, radiographic
examination of the thorax was performed, revealing several pulmonary nodules.
Results
Differential diagnoses of the radiolucency in the third phalanx included osteomyelitis,
neoplasia or a cystic lesion. Based on the history and the clinical and radiological findings,
osseous metastasis was suspected. The mare was euthanized. Post-mortem histopathological
examination confirmed the diagnosis of primary renal adenocarcinoma with metastases to the
lungs, the myocardium, along the perirenal lymphatic tract and to the third phalanx, with
extensive osteolysis in the latter location. Post-mortem computed tomography of the hoof
provided superb visualisation of the osseous metastasis.
Conclusion
Osseous metastatic neoplasia should be included in the differential diagnosis of severe
lameness in aged horses with a history of chronic renal disease.