Key Clinical MessageAlthough resection of multilobular tumors of bone can be associated with a good prognosis and long disease‐free intervals in dogs, osteosarcomatous transformation should be considered a cause for rapid recurrence of clinical signs.

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Summary A 17‐year‐old Irish Draught cross gelding with a history of chronic recurrent right hindlimb cellulitis was evaluated due to acute onset of severe lameness affecting this limb. Scintigraphic examination identified marked radiopharmaceutical uptake within the central and third tarsal bones and the lameness improved following tibial and peroneal nerve blocks. Distal intertarsal joint collapse was observed but the radiographic changes were considered insufficient to explain the lameness severity. Magnetic resonance imaging revealed marked bone pathology affecting both the central and third tarsal bones. A subcutaneous abscess developed on the dorsolateral aspect of the limb, but clear evidence of joint infection was not established. Computed tomography showed lytic lesions affecting mainly the third tarsal bone, so the animal was treated surgically for suspected osteomyelitis involving this bone by implantation of gentamicin impregnated polymethylmethacrylate. Shortly following surgery the horse developed gastric rupture and was euthanased. Osteonecrosis of the third tarsal bone was identified, but sepsis was not demonstrated to be the cause. It is hypothesised that osteonecrosis developed as a sequel to chronic osteomyelitis which may have responded to previous antimicrobial treatment. The report also highlights the importance of gastric disorders as a differential for discomfort in animals undergoing treatment for orthopaedic disease.

In humans, idiopathic orbital inflammation (IOI) is a diagnosis attributed to benign, inflammatory orbital conditions without identifiable local or systemic cause. We describe the clinical signs, imaging and histopathological findings, management and outcome of four dogs diagnosed with IOI. Methods: Multicentric retrospective study.Results: A total of four dogs (five orbits) of three different breeds (three cases were English Springer Spaniels [ESS] or ESS-cross) and ages ranging from 3 to 12 years were included. Initial presenting signs were unilateral and included exophthalmos, enophthalmos, globe deviation, thickening and protrusion of the third eyelid and conjunctival hyperemia. Computed tomography and magnetic resonance imaging identified heterogeneous space-occupying, contrast-enhancing orbital lesions in all cases. Sparing of the retrobulbar space was detected in four of five orbits. Histopathology revealed mixed inflammatory infiltrates of lymphocytes, plasma cells, and histiocytes. Immunohistochemistry was performed in two cases highlighting the presence of histiocytes and lymphocytes, predominantly T cells.Resolution of clinical signs was achieved in two cases managed with oral immunosuppressant medication (corticosteroids alone or combined with cyclosporine or azathioprine), one went into spontaneous remission, one resolved with topical corticosteroids, and one underwent exenteration. Recurrence occurred in two cases within 15 months of initial diagnosis and required further immunosuppressant medication. One case developed signs in the contralateral orbit within 8 months of presentation.Conclusions: IOI is an uncommon condition in dogs. Its diagnosis relies on the combination of advanced imaging and histology. As in humans, it appears that spontaneous remission and recurrence may occur requiring long-term immunosuppressant medication.