Case reveal


  • The cardiac silhouette is severely enlarged with a rounded contour, dorsally displaces the trachea and carina, and is border effaced with the diaphragm.
  • Within the ventral aspect of the pleural space, there is a severe amount of soft tissue opaque material, that is border effacing with the cardiac silhouette and the ventral body wall.
  • There is mild increased soft tissue opacity in lung lobes caudodorsal to the cardiac silhouette, with decreased visualization of the pulmonary vasculature.


1. Severe globoid cardiomegaly with severe pleural effusion and caudodorsal unstructured interstitial pulmonary pattern. In combination with the pleural effusion, the presence of pericardial effusion and cardiogenic pulmonary secondary to right +/- left-sided heart is considered (r/o endocarditis, myxomatous valvular disease, or neoplasia). The presence of atelectasis within the lungs due to the pulmonary hypoinflation is also considered.

Thoracic and Abdominal Ultrasound

  • A large amount of anechoic effusion is identified within pericardial, peritoneal and pleural cavities. The lungs contain regions of consolidation. A brief echocardiogram did not reveal valve thickening.

Case outcome

  • 8 L of fluid was removed from the pleural space on the left side. Cytology of the
    pleural fluid and peritoneal fluid revealed increased neutrophils without evidence of sepsis
    (neutrophils nondegenerate, no bacteria seen).
  • Due to quality of life concerns and severity of disease, humane euthanasia was elected.


  • Pericarditis and epicarditis, fibrinous and suppurative, diffuse, chronic, severe, with massive effusion and pericardial enlargement. A thymoma was identified in the outer portion of the pericardium (confirmed with immunohistochemistry for cytokeratin). There was no connection between the thymoma and the effusion, and the thymoma seemed limited to the outer portion of the pericardium, so it was not determined if the thymoma could have been related to the effusion/inflammation.
  • Pleural and peritoneal effusion was consistent with right-sided cardiac compromise secondary to pericardial effusion.

A little bit more…

  • Pericardial effusion and right-sided heart failure is uncommon in horses (Freestone et al., Worth et al.)
  • Clinical signs may include tachycardia, ventral cervical/pectoral edema, jugular distention and muffled heart sounds and/or presence of pericardial friction rubs (Malalana et al., Freestone et al., Worth et al., Bernard et al.). The most common presenting clinical signs are not specific for pericarditis and include fever (in cases of septic pericarditis), anorexia and lethargy. Horses may also present with signs of colic.
  • Right-sided congestive heart failure in horses has been reported to occur secondary to tricuspid insufficiency, pulmonic stenosis, cor pulmonale, and congenital defects (Hargreaves et al.). Less commonly a consequence of pericardial effusion and cardiac tamponade (Hargreaves et al.).
  • Reported causes of pericardial effusion may include immune-mediated processes, bacterial infection, viral infection, trauma and neoplasia. Most often, a cause is not identified (Malalana et al.).
  • Hargreaves et al. identified multicentric lymphoma as a cause of pericardial effusion and right-sided heart failure in a case. Malignant thymoma has rarely been reported to affect horses; however, several case reports of horses with cranial mediastinal masses with pericardial involvement +/- pericardial effusion have been described. One of them was a Percheron mare with confirmed squamous cell carcinoma (Whiteley et al.) and a 18-year-old Tennessee Walking Horse diagnosed with a type A thymoma (Shahriar et al.).
  • Three forms described (may overlap) (Worth et al., Malalana et al., Bernard et al.):
    • Effusive pericarditis: accumulation of fluid in the pericardial sac.
    • Fibrinous pericarditis: accumulation of fibrin in the pericardial sac, along the parietal pericardial surface (with or without effusion).
    • Constrictive pericarditis: fibrosis and thickening of the pericardial sac, subsequently restricting diastolic filling and altering cardiac function (possible consequence of pericardial inflammation or the deposition of fibrin within the pericardial sac, or a complication of any insult to the pericardium). 
  • Pericardial effusion may be characterized as follows:
    • transudate
    • modified transudate
    • exudates (inflammatory, noninflammatory)
    • hemorrhagic
  • Thoracic radiographs are of limited value to identify pericardial effusion but may help screen for cardiomegaly and signs of failure (Malalana et al.). Ultrasound is the preferred modality of choice (allows identification of the pericardial fluid space and differentiation from pleural effusion).
Long axis 4 chamber view from the right side. The pericardial sac contains a large amount of anechoic effusion with subsequent partial collapse of the right ventricle (Malalana et al.)
  • Therapeutic pericardiocentesis is warranted in horses with cardiac tamponade +/- heart failure (Malalana et al., Bernard et al.).
  • Previously deemed to have a guarded prognosis; however, improved response noted with aggressive therapy (Worth et al., Bernard et al.). Partial pericardiectomy may be successful in some cases (Malalana et al.).


  • Malalana, F., D. Bardell, and S. McKane. “Idiopathic aseptic pericardial effusion with cardiac tamponade in a horse.” Equine Veterinary Education 23.2 (2011): 64-68.
  • Worth, Leila T., and Virginia B. Reef. “Pericarditis in horses: 18 cases (1986–1995).” Journal of the American Veterinary Medical Association 212.2 (1998): 248-253.
  • Bernard, William, et al. “Pericarditis in horses: six cases (1982-1986).” Journal of the American Veterinary Medical Association 196.3 (1990): 468-471.
  • Freestone, J. F., et al. “Idiopathic effusive pericarditis with tamponade in the horse.” Equine veterinary journal 19.1 (1987): 38-42.
  • Hargreaves, Laura, Lara Gosling, and Jonathon J. Dixon. “Pericardial effusion and congestive heart failure in a horse with multicentric lymphoma.” Veterinary Record Case Reports6.3 (2018): e000631.
  • Davis, E. G., and B. R. Rush. “Diagnostic challenges: equine thoracic neoplasia.” Equine Veterinary Education 25.2 (2013): 96-107.
  • Shahriar, Farshid, and Janet Moore. “Thymic epithelial tumor with heart metastasis in a horse.” Veterinary Medicine International 2010 (2010).
  • Whiteley, L. O., et al. “Malignant squamous cell thymoma in a horse.” Veterinary pathology 23.5 (1986): 627-629.