Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared to ___ , lungs remain clear . There may be a small left pleural effusion . No right pleural effusion . No pneumothorax . Unchanged mild cardiomegaly . Mediastinal and hilar contours are unchanged . No pulmonary vascular congestion . Unchanged deformity of the right posterior fourth rib .
    OUTPUT:
    
Possible trace left pleural effusion . Otherwise , no acute cardiopulmonary process .