atelectasis

A month ago, I had a chest x-ray because the doctor thought I had
pneumonia.. The radiologist's impression was "Minor subsegmental areas of atelectasis are suspected along the left lung base, without definite evidence of vascular decompensation or acute infiltrate"  
I was to have a follow-up x-ray done in a month, which I did, and the impression rather than being normal was "There is a slight increase in the disk atelectasis at the lung bases.  There is no acute pneumonic process or pulmonary vascular congestion."  Could you please tell me what a "disk atelectasis" is, and what this might mean.. or the possible causes?
I am a little worried..
Thank you..

[National Jewish]

Disk or platelike atelectasis is collapsed areas of the lung that have a linear or horizontal appearance.  They look like a CD, viewed from the side.  They occur with a blood clot or clots to the lung, but more often they occur without any significant lung disease.
You should discuss this with your doctor.  You should have another X-ray in a month and, if these findings persist, it may be necessary to do further testing, such as a CT scan or a Lung Scan.