Whay does this mean " the lung fields are clear and consider perihilar pneumonitis, bilateral? can my son still go with his operation/surgery?

Depends on situation: If the kid will be placed under an inhaled general anesthesia, such a reading on an x-ray might lead the treatment team to delay an elective operation. A lung disorder can be aggravated by inhaled anesthetics & lead to worsening of the lung status. Discussion of the findings with your doc is indicated.

See below: Your anesthesiologist will want to know more information. This will include temperature elevations, elevated white counts, and symptoms. Why did they do a chest x-ray in the first place. If everything else looks okay, we might proceed.