Multidetector-row CT features and histopathological analysis of pericardial recesses in dogs

Linda Negro, Alessia Cordella, Arianna Costa, Laura Nordio, Giovanna Bertolini

Background: Pericardial recesses (PRs) are fluid-filled pockets of the pericardium that can be mistaken for other mediastinal structures or pathologies. The aim of the study was to describe the location and appearance of PRs in dogs using MDCT and to develop a dedicated imaging technique for their assessment.

Methods: The study was a single-center observational and descriptive study that included 30 mesaticephalic dogs with pre- and postcontrast CT series, and 180 dogs of different breeds and morphologies that underwent thoracic CT scan for various purposes. The CT images were analyzed using multiplanar reformations and volume rendering techniques to identify and characterize the PRs. Two dogs that died for unrelated causes underwent necropsy and histological examination of the pericardium and PRs.

Results: Two types of PRs were identified at the level of the transverse sinus of the pericardium: the aortic recess and the pulmonic recess. A third pericardial fluid-containing structure was seen in a few cases, at the level of the termination of the caudal vena cava into the right atrium. PRs were identified as fluid-attenuating, non-enhancing structures showing varied appearance. A dorsal, slight oblique multiplanar section through the aortic bulb resulted the best technique for visualization of all the recesses. Histopathological evaluation confirmed the presence of pocket-like reflections of the pericardium lined by mesothelium.

Limitations: The study had some limitations, such as the relatively low number of cases included, the confirmation with histological exam only in two cases, and the lack of assessment of the prevalence and variation of PRs in different dog types or breeds, as well as the variation of PRs during different cardiac phases.

Conclusions: This study describesthe normal CT appearance of the pericardial recesses in dogs and developed a dedicated visualization technique for their assessment. Knowledge of the CT appearance of the pericardial recesses is necessary to avoid their misinterpretation and subsequent unnecessary invasive investigations.

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