Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A rounded retrocardiac opacity likely represents a small hiatal hernia . Atelectasis is noted at the left lung base . The right lung and left upper lung appear clear without lobar consolidation , pleural effusion , pneumothorax , or pulmonary edema . The cardiomediastinal silhouette is unchanged appearance .
    OUTPUT:
    
Small retrocardiac hiatal hernia with adjacent atelectasis . Otherwise , no evidence of acute cardiopulmonary process .