Sounds like you had a CT scan, or an MRI. Air-fluid levels indicate that there is fluid sitting stagnant in the sinuses, which is abnormal and suggests that they are not draining well. Thickening of the mucosa lining the walls implies inflammation, often chronic.
Sinuses are normally air-filled spaces, lined with a mucus-secreting tissue. The mucus drains out of the sinuses into the nasopharynx and is normally swallowed, or in disease states, sneezed or coughed out. When the orifices of the sinuses become blocked by swelling due to allergy or viral disease, fluid accumulates in the sinuses. The fluid is protein-rich, and the sinuses are not sterile environments, so they often turn into bacterial culture sites, thus acute sinusitis.
The treatment of sinusitis involves two things -- controlling the bacterial overgrowth, and getting the fluid in the sinuses to drain. This often involves addressing the underlying cause of the blockage, by treating allergies with desesitization or with topical steroids, and by treating congestion with decongestants. Antibiotic treatment for sinusitis is generally prolonged, as there is not good penetration of antibiotics into the sinus spaces. Two to four weeks of antibiotic therapy is often required, and multiple courses of antibiotics may be necessary.
Surgery for chronic sinusitis is aimed at increasing the openings between the sinuses and the nasopharynx, and thus permitting fluid drainage.
In addition to pharmacologic therapy, some people seem to get good results with saline nasal irrigations. I know some SBers recommend a Neti pot for doing this.
The big risk of sinus disease and diving is failure to equalize, whether descending or ascending. This can be extremely painful, and a cause of post-dive headaches.
I would guess that your PMD will most likely start you on antibiotics, and possibly nasal steroids. Those would be typical approaches. If your condition does not respond to basic therapy, a referral to an ENT doc would be in order.
Obviously, this is not specific advice aimed at you individually, but simply a brief discussion of the main points about sinusitis. Hope it's helpful.
