There are multiple old left-sided rib fractures with associated pleural thickening and blunting of the left costophrenic angle. An ill-defined opacity measuring approximately 18 mm in maximal diameter is seen over the anterior end of the left fourth rib, likely representing callus formation around a healing rib fracture, as there is no corresponding abnormality on the lateral view.
Acute rib fracture (Absent) Pleural scarring (Present)