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

At the level of pericardial reflections and near the great thoracic vessels, pericardial recesses (PRs) are present, where fluid can collect to increase the pericardial reserve volume. To date, these structures have not been described in vivo in veterinary patients. The aims of this observational and descriptive study were to describe the location and appearance of PRs in dogs, as seen with multidetector-row CT (MDCT), and to develop a dedicated imaging technique for their best visualization. Dogs who underwent MDCT examination of the whole body were included in the study and CT data were retrospectively evaluated. Dogs with any thoracic abnormality were excluded. MDCT analysis of the PR's was compared with the pathological features of PRs. PRs were identified as fluid-attenuating (10-30 HU), non-enhancing structures showing varied appearance. Two types of PRs were identified at the level of the transverse sinus of the pericardium and classified on the basis of their anatomic location: the aortic recess and the pulmonic recess. A third pericardial fluid-containing structure was seen in a little number of cases, at the level of the termination of the caudal vena cava into the right atrium. A dorsal, slight oblique multiplanar section through the aortic bulb resulted the best technique for visualization of all the recesses. Anatomo-pathological evaluation confirmed the location and the presence of pocket-like reflections of the pericardium identified with 3D-CT models. Knowledge of the CT appearance of the pericardial recesses is necessary in order to avoid their misinterpretation and subsequent unnecessary invasive investigations.