The Descending Aorta Distinguishes Between Pleural and Pericardial Fluid

This week’s image is brought to us by Drs. Patrick Thomas and Scott Kurpiel. It is a parasternal long axis image with evidence of both a pericardial effusion and a left pleural effusion. 

The view is obtained by placing the probe at the left sternal border in the 3^rd or 4^th intercostal space. The indicator is pointed toward the patient’s right shoulder.

 The ideal image in this axis will show us a cross section of both the mitral valve and the aortic valve- achieving this may require some slight fanning or rotation of the probe. This still image is taken in diastole- the MV leaflets are open and the septal leaflet is slapping the septum (a marker of good LV function).  Beneath the heart we see the descending aorta in cross section. Make sure that you have enough depth to see this key landmark. It is vital for  distinguishing a left pleural effusion from a pericardial effusion. The pericardium tracks anterior to the descending aorta and thus a pericardial effusion will do the same. Pleural effusion will track posterior to the aorta within the pleural space as seen in this image.  Making these  diagnoses correctly can be life saving in the patient with undifferentiated hypotension or dyspnea.