Use of Acrylic Resin to Fill the Orbital Cavity after Exenteration in a Dog with Conjunctival Hemangiosarcoma

Abstract

Background: The hemangiossarcoma (HSA) is a malignant tumor originated from the alterations of vascular endothelial cells. As it has an aggressive behavior, it is indicated, as initial treatment, wide surgical excision, such as the exenteration, which results in the surgical removal of the ocular bulb and adjacent tissues. The referred technique has as a result a concave orbit and aesthetically unacceptable. Therefore, various materials, used as orbital implants, have been studied and used in several species. Thus, it was aimed to report the use of the polymethylmethacrylate (PMMA) to fill the orbital cavity after exenteration in a dog with conjunctival HSA.

Case: A 10-year-old male Pitbull dog was assisted, with a clinical history of growth of a reddish tissue in the left eye, causing constant hemorrhage, with an evolution of two months. At ophthalmic examination of the left eye, in the temporal bulbar conjunctive was found a reddish neoformation, with an irregular surface, measuring approximately 4x2x2 cm. The biopsy and aspiration cytology of the neoformation, revealed cells that inferred that they were those of conjunctival HSA. The hemogram revealed normocytic anemia; the biochemical profile was with the standards of normality and no metastasis were found in the ultrasonography and X-ray. The treatment of choice was the exenteration. Initially, the palpebral borders were approximated using continuous simple suture wit monofilament nylon thread. An incision was made in the skin, along the orbital rim and then was performed a rhombus dissection of the conjunctive and all the extraocular muscles. Next, the eye globe, together with the neoplasia, soft tissues of the orbital cavity and third eyelid were removed. The PMMA was obtained from a mixture of the powder (polymer) and of the liquid (monomer) in the ratio of 1:1 in a sterile recipient, in order to obtain a liquid suspension. Still in its paste-like form, the PMMA was molded in the orbit itself without going beyond its limits, filling in. At the moment of the polymerization of the PMMA, the site was irrigated with cold sterile saline solution for the reduction of the temperature caused by the thermal reaction. For the closing of the conjunctive, a continuous simple suture was performed, using 910 4-0 polyglactin thread and, in the suture of the skin, simple interrupted stiches were used with 3-0 monofilament nylon thread. After the surgery, tramadol hydrochloride was administered at a dose of 2 mg/kg/SC and meloxicam at a dose of 0.1 mg/kg/SC.  In the post-operative phase, the animal was treated with ampicillin suspension at a dose of 20 mg/kg/TID/PO during 10 days; metronidazole at a dose of 15 mg/kg /BID/PO during 10 days and the application of 0.5% chloramphenicol ocular ointment, 10.000UI of retinyl acetate and 2.5% amino acids on the stiches, SID, until their removal. After nine months, the owner reported a satisfactory result in relation to the aesthetic aspect, denying the presence of any ocular alterations or discomfort of the animal.

Discussion: The use of the PMMA implant proved to be an excellent alternative to fill the anophthalmic cavity after exenteration in a dog with conjunctival HSA, seen as it provided, most importantly, the maintenance of the orbital volume, granting an adequate aesthetic aspect, already established among some authors, without the presence of secretion, inflammation and local infection.  It is worth emphasizing that, despite the patient in question having been treat with a broad-spectrum antibiotic after the surgery, in other reports, the absence of local infection was associated to the high temperature that the PMMA reaches during the exothermic reaction in the polymerization stage. Furthermore, the referred implant is cost-effective, offers easy molding to the orbit and absence of extrusion. In light of this, it is therefore suggested that the referred implant is a pertinent alternative for use in similar cases.