What Does the following chest X-ray Indicate? 

Dear Doctor,

I fractured my left anterior fifth rib, near the costochondral junction (nondisplaced, nonangulated). This was followed by atelectasis due to splinting. My chest x-ray shows mild blunting of the left pleural angles and appears to represent a small pleural effusion.

I am 51 years old and in otherwise good health. How serious is this condition and what is the best treatment to pursue?

Thank you