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EQUINE VETERINARY EDUCATION / AE / OCTOBER 2014
right hindlimb. The distal aspect of the affected limb was bandaged and marked swelling was present around the right stifle and femoral area. Ultrasonographic evaluation revealed similar but more extensive pathology than previously: the haematoma-like structure extended from the caudal proximal femur to the caudal aspect of the proximal tibia. Treatment with ceftiofur (Excenel, 2.2 mg/kg bwt i.v. q.
12 h)5, phenylbutazone (2.2 mg/kg bwt i.v. q. 12 h) and i.v. crystalloid fluids (50 ml/kg bwt/24 h) was initiated. Haematological analysis revealed leucocytosis of 14.09 ¥ 109 cells/l with 12.79 ¥ 109 mature neutrophils/l. Prothrombin time was 11.2 s and partial thromboplastin time 37.5 s, matching those of a healthy control horse. Serum urea and creatinine were within normal limits. Morphine (0.12 mg/kg bwt q. 8 h) and xylazine (Chanazine 2%, 0.012 mg/kg bwt q. 8 h)9 were administered via an epidural catheter. To decrease the risk of gastrointestinal impaction, 4 l of liquid paraffin with 4 l of water were administered via nasogastric intubation. During the following 4 days the PCV oscillated between 15
and 21%. The right limb was maintained in a distal limb bandage with a plantar splint, although the horse would not bear weight on this limb. A support bandage and frog support with high-density polystyrene wedges were applied to the left hindlimb. The systemic antimicrobial coverage was extended by adding metronidazole (20 mg/kg bwt per rectum q. 8 h). By the second day after re-admission the horse showed increased levels of discomfort. Ultrasonographic examination revealed similar findings to the previous scan. Purulent exudate was observed draining from the incision site: the packing was removed and profuse bleeding from the incision occurred. The incision was re-packed with sterile gauze. The epidural catheter was no longer patent and was removed. Pain medication consisting of a constant rate infusion of ketamine (0.6 mg/kg bwt/h i.v.) was started. The following day the horse appeared more comfortable and would intermittently bear full weight on the affected limb. However, a day later the stallion became recumbent, showed severe signs of discomfort and was humanely destroyed.
Post mortem findings The right hindlimb had a comminuted mid-shaft femur fracture with regional haemorrhage. Muscle surrounding the fracture area had numerous small (0.1–1.5 cm) multifocal, red, poorly defined, slightly nodular lesions resembling haematomas (Fig 3); similar lesions were seen in the caudal internal abdominal wall (Fig 4), mesentery, on both diaphragmatic surfaces, in the endocardium and scattered in the myocardium. The multilobular right deep inguinal lymph node was enlarged (largest lobule approximately 6 cm in diameter), haemorrhagic and patchily necrotic on the cut surface (Fig 5). A large, elongated, clotted haematoma (70 cm in length and from 10–15 cm in irregular diameter) occupied the groove between 2 muscle bellies of the biceps femoris muscle and tapered off below the stifle and above the lateral aspect of the tarsus (Fig 6). The lungs, spleen and kidneys appeared macroscopically normal. Specimens of affected muscle from the right hindlimb, as well as the affected lymph node and a mesenteric serosal nodule were preserved in 10% neutral buffered formalin for routine sectioning and staining with haematoxylin and eosin. The disembodied femur was radiographed, showing moderate osteopaenic bone in the area of the severely comminuted fracture (Fig 7). Fracture-site
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Fig 3: Post mortem examination of the right hindlimb perifemoral musculature. Red and yellow mottling is present due to multifocal small haemangiosarcomas (white arrow) often embedded in fibrous connective tissue.
Fig 4: Post mortem: caudal abdominal wall showing multifocal small nodular metastatic haemangiosarcoma (white arrow) and some petechiae and ecchymoses (black arrow).
bone was decalcified in formic acid before sectioning and staining. Immunohistochemical (IMH) staining using a standard avidin-biotin technique (Haines and Chelack 1991) for factor VIII-related antigen was applied to representative sections from muscle, mesentery and fracture-site bone, and all sections examined by light microscopy.
Histopathological findings The right hindlimb muscular and abdominal serosal nodules comprised variably-sized irregular blood-filled spaces, which were either encapsulated or infiltrating into muscle. The nodules were lined by either a single layer of small or pleomorphic, plump, neoplastic endothelial cells, or multilayered, spindle-cell dense, irregularly thickened walls (Fig 8), sometimes thrown into folds, and with robust supporting connective tissue. The deep inguinal lymph node parenchyma was mostly replaced by large areas of
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