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 helica l computed tomography (CT) appearance of near-water-density structures situated posterior to the pulmonary trunk and right main pulmonary ar tery, and to consider the implications of these CT images. METHODS. Th ree-millimeter-thick helical CT scans of the mediastina of 133 patient s were reviewed to determine the incidence and range of appearance of near-water-density structures situated posterior to the pulmonary trun k 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 descripti ons 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 perica rdial cavity proper, The locations of the structures corresponded to t he 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 posterio r to the pulmonary trunk and right main pulmonary artery in patients w ithout obvious pericardial effusion were concluded to be physiologic f luid collections in the recesses of the transverse and oblique sinuses .