Fluid collection in the pericardial sinuses and recesses - Thin-section helical computed tomography observations and hypothesis

RATIONALE AND OBJECTIVES. This study describes the thin-section helical computed tomography (CT) appearance of near-water-density structures situated posterior to the pulmonary trunk and right main pulmonary artery, and to consider the implications of these CT images. METHODS. Three-millimeter-thick helical CT scans of the mediastina of 133 patients were reviewed to determine the incidence and range of appearance of near-water-density structures situated posterior to the pulmonary trunk and right main pulmonary artery, Thin-section helical CT appearance was compared with that of fluid collection in the pericardial sinuses and recesses of patients with pericardial effusion, and with descriptions of the pericardial sinuses and recesses in the literature. RESULTS. Near-water-density structures showing varied appearance ranging from bands to mass-like densities were observed on thin-section helical CT images of 49 patients (37%) who had no obvious effusion in the pericardial cavity proper, The locations of the structures corresponded to the sites of recesses in the transverse and oblique sinuses, and their appearance was similar to that of fluid in the pericardial sinuses and recesses. CONCLUSION. Near-water-density structures situated posterior to the pulmonary trunk and right main pulmonary artery in patients without obvious pericardial effusion were concluded to be physiologic fluid collections in the recesses of the transverse and oblique sinuses.