Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest films were obtained with patient in upright position . Comparison is made with the next preceding portable single view chest examination of ___ . Patient is not examined in upright position using PA and lateral projections . Moderate enlargement of heart silhouette in comparison with the preoperative chest examination of ___ . In addition to the previously existing bypass surgery , the patient has now received an aortic valve prosthesis ( metallic components identified suggest porcine valve ) located in appropriate position . On the lateral view prostheses replaces the previously identified star shaped heavy aortic valve calcifications . Present cardiac enlargement is likely the result of some postoperative pericardial effusion . The distance between surgical graft clips and outer cardiac contour has increased . On the frontal view , mild blunting of the lateral pleural sinuses is seen . On the right side , some fluid enters also the minor fissure . These findings are rather small and on the lateral view only mild blunting of the posterior pleural sinuses is noted . Linear density in the left lung base in retrocardiac position suggests presence of a left lower lobe posterior atelectasis . It was not present on the preoperative examination . There is no evidence of pneumothorax in the apical area and the pulmonary vasculature demonstrates no evidence of increased congestion at this time . The next preceding portable chest examination of ___ identified basal densities most likely represented pleural effusions that were partially layering in the posterior pleural compartments .
    OUTPUT:
    
Porcine aortic valve prosthesis is in place , postoperative enlargement of cardiac contours with no evidence of pulmonary vascular congestion . Bilateral small pleural effusions and partial atelectasis in left lower lobe posterior segment . No pneumothorax . Followup examination in a month or two is recommended to document resolution of these postoperative changes .