COMPANION ANIMALS
Post-surgical death and acute thymic hemorrhage in a young dog
Jan Shapiro, Kris Ruotsalo
A 6-mo-old male Golden Doodle dog was submitted to the Animal Health Laboratory in Kemptville for postmortem. Three days prior to death, the dog had undergone surgery for routine castration, had recovered from anaesthesia uneventfully, and was discharged from the clinic the same day. Pre-anesthetic hematology had shown no abnormalities. The day after surgery, the dog was re-presented to the clinic, as the owner was concerned about continuous dripping of blood from the castration incision. On clinical examination, the attending veterinarian noted excessive bruising of the scrotum, and when questioned, the owner mentioned that they felt that the dog had experienced excessive bleeding when it was teething. The following day, bleeding from the surgery site seemed to have stopped, but the dog was weak, lethargic, and had an increased respiratory effort. Oral mucosa was pale, and scrotal bruising was worse. A CBC showed low values for red blood cell counts, and low hematocrit, hemoglobin, MCHC, and total protein, with a platelet count within the normal range. Anemia due to blood loss was diagnosed, and the decision was made to send the dog to a referral clinic, but the dog died en route.
At postmortem, there was extremely marked generalized pallor. The thoracic cavity held ~ 175 mL of unclotted blood. In the left cranial thorax, there was an 8 x 5 x 2 cm solid hematoma dissecting throughout the thymus (Fig. 1), leaving various sized islands of compressed pale lobules. The adjacent mediastinum and the pericardial sac were markedly expanded with clotted blood, and ~ 2 mL of unclotted blood was in the pericardial sac. Dissecting hemorrhage extended cranially in the soft tissue encircling the distal 1/3 of the trachea. Dissecting hemorrhage also encircled the intra-thoracic aorta, vena cava, and esophagus. No abdominal hemorrhage was observed. There was marked swelling of the scrotum with a large solid hematoma, and the scrotal skin, including the incision which had focally dehisced, was covered with dried blood. Hemorrhage extended cranially for several cm into the subcutis and fascia of external abdominal oblique muscle and into the soft tissue around the penis, but did not extend into the abdominal or pelvic cavities. A specific vascular site of origin of the scrotal hemorrhage could not be found.
The postmortem diagnosis was severe anemia associated with post-castration scrotal hemorrhage, and thymic hemorrhage, with severe secondary hemothorax, hemopericardium and hemomediastinum. Histopathology of the thymus showed hemorrhage.
Severe thymic hemorrhage or thymic hematoma is a well-recognized condition of young dogs that is often fatal because of hypovolemic shock secondary to massive mediastinal hemorrhage. Reported causes of thymic hematoma include severe trauma directly to the thorax, or to the thymus by over-extension of the neck or excessive pulling on the dog’s collar, dissecting aortic aneurysms, bleeding thymic neoplasms, and various coagulation disorders, including vitamin K- responsive coagulopathy and anticoagulant rodenticide toxicosis. Spontaneous idiopathic thymic hemorrhage of young dogs 3-9 mo of age is a rare disease, diagnosed by exclusion of other causes, with the underlying predisposing factor being fragility of the thymus associated with age-associated atrophy.
The reason for the thymic hemorrhage could not be confirmed in this dog. A pre-existing coagulation disorder was suspected, based on the owner’s comment about previous excessive teething hemorrhage, but could not be proven without corroborating clinical pathology and coagulation profile data. Toxicology testing was not performed. AHL
References
Liggett AD, et al. Thymic hematoma in juvenile dogs associated with anticoagulant rodenticide toxicosis. J Vet Diagn Invest 2002;14:416-419.
Williams LJ, et al. Pathology in Practice. J Am Vet Med Assoc 2014;244:905-907.
Figure 1. Acute thymic (arrow), mediastinal, and pericardial sac hemorrhage