Is atelectasis an emergency? i have wedge shaped density at right base. right lower lung.

Not usually.: it is probably an old issue,, but follow up with your doctor, especially if having any breathing issues.

Not really: Atelectasis just reflects the level of inflation of a part of the lung. If you did not take a deep breath during the x-ray, if you had a little mucus plugging, if your lifestyle has you quiet & sedentary , these all can give you a mild atelectasis that would disappear with more activity or deeper breathing. It is not a sign of bad disease or something worrisome.