An incidental bulge with a congenital cause: imaging clues to canine pericardial defects

Congenital partial pericardial defect affecting the right ventricle in a dog

K. Sugimoto; K. Sasaki; S. Yamamoto; M. Yonemaru; N. Shimada; K. Kutara; J. Hiroma

Background

Congenital pericardial defects (PDs) are rare cardiac anomalies in dogs and are often discovered incidentally, frequently at necropsy or during unrelated surgical procedures. Antemortem diagnosis is uncommon due to the absence of clinical signs and the difficulty of visualizing the pericardium with routine imaging. This report describes a case of a congenital partial pericardial defect involving the right ventricle in a dog, highlighting characteristic multimodal imaging findings and the diagnostic value of fluoroscopy.

Methods

A 1.8-year-old, 7.7-kg male mixed-breed dog underwent cardiovascular evaluation as part of a routine pre-castration examination. Diagnostic assessment included physical examination, complete blood count, serum biochemistry, electrocardiography, thoracic radiography, echocardiography, fluoroscopy, and non–ECG-gated contrast-enhanced computed tomography under general anesthesia. Imaging findings were interpreted to identify structural cardiac abnormalities and to differentiate among possible causes of an abnormal cardiac silhouette.

Results

The dog was clinically asymptomatic, with normal physical examination findings, laboratory results, and electrocardiography. Thoracic radiographs revealed mild cardiomegaly with a focal bulging of the cardiac silhouette. Echocardiography demonstrated partial absence of the pericardial line in the right ventricular outflow tract and right ventricular dilation, without evidence of other causes of right ventricular enlargement. Fluoroscopy identified a vigorous, paradoxically pulsating bulge in the right ventricular region. Computed tomography showed a balloon-shaped protrusion of the right ventricular lumen extending cranially near the pulmonary infundibulum. Based on these findings, a diagnosis of congenital partial pericardial defect with right ventricular herniation was made.

Limitations

This report describes a single clinical case, limiting generalizability. Long-term outcomes and the natural progression of right-sided partial pericardial defects in dogs could not be assessed. Additionally, advanced imaging modalities such as cardiac magnetic resonance imaging, considered the diagnostic gold standard in humans, were not performed.

Conclusions

Congenital partial pericardial defects in dogs may be clinically silent and detected incidentally during routine examinations. Multimodal imaging is essential for diagnosis, with fluoroscopy providing valuable dynamic information suggestive of pericardial defects. Computed tomography can confirm cardiac herniation and delineate anatomic details. This case underscores the importance of considering pericardial defects in the differential diagnosis of focal cardiac silhouette bulging, even in asymptomatic canine patients.

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