Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP portable upright view of the chest . Patient 's chin obscures the superior mediastinum and portions of the lung apices . The lung volumes are low also limiting evaluation . The heart is moderately enlarged though this appears unchanged . Retrocardiac space is poorly assessed . Otherwise , there is no evidence of pneumonia . No large effusion or pneumothorax . Mediastinal contour stable . Bony structures are intact .
    OUTPUT:
    
No convincing evidence for pneumonia though left lung base poorly visualized . Cardiomegaly unchanged .