Sinus Infection (Sinusitis)

How is sinus infection diagnosed?

Sinus infection is most often diagnosed based on a history and examination made by a doctor. Because plain X-ray studies of the sinuses may be misleading and procedures such as CT and MRI scans, which are much more sensitive in their ability to diagnose sinus infection, are so expensive and not available in most doctors' offices, most cases of sinus infection are initially diagnosed and treated based on clinical findings on examination. These physical findings may include:

  • redness and swelling of the nasal passages,
  • purulent (pus like) drainage from the nasal passages (the symptom most likely to clinically diagnose a sinus infection),
  • tenderness to percussion (tapping) over the cheeks or forehead region of the sinuses, and
  • swelling about the eyes and cheeks.

Occasionally, nasal secretions are examined for secreted cells that may help differentiate between infectious and allergic sinusitis. Infectious sinusitis may show specialized cells of infection (polymorphonuclear cells) while allergic sinusitis may show specialized cells of allergy (eosinophils). Physicians prescribe antibiotics if bacterial infection is suspected. Antibiotics are not effective against viral infections; many physicians then treat the symptoms.

If sinus infection fails to respond to the initial treatment prescribed, then more in-depth studies such as CT or MRI scans may be performed. Ultrasound has been used to diagnose sinus infections in pregnant women, but is not as accurate as CT or MRI. Rhinoscopy or endoscopy, a procedure for directly looking in the back of the nasal passages with a small flexible fiber optic tube, may be used to directly look at the sinus openings (ostea) and check for obstruction of these openings by either swelling or growths.

It may sometimes be necessary to perform a needle aspiration (needle puncture) of a sinus to get infected material to culture to determine what pathogen is actually causing the sinus infection. Cultures of the nasal passages are rarely helpful in determining what bacteria or fungus is causing a sinus infection since the nasal passages are often colonized by non-infecting bacteria. The needle puncture procedure is usually done by an otolaryngologist when treatments have failed to alleviate the disease. The procedure requires local anesthesia to minimize any discomfort; some patients require general anesthesia. The sinus is aspirated, the contents sent for culture and staining, and the sinus may be flushed with a saline solution. This is technically the most accurate way to diagnose infectious sinusitis.

In addition, both rigid and flexible endoscopy has been used to obtain diagnostic material from sinuses. These procedures are usually done by an otolaryngologist after topical and local anesthesia. Occasionally, there may be a need to sedate the patient. Some investigators suggest that endoscopy specimens are comparable to those obtained by needle puncture.

Fungal infections are usually diagnosed by such biopsy procedures and tissue removed by a surgeon, or by fungal culture and microscopic identification by a microbiologist or pathologist trained to identify fungi. Allergic fungal sinusitis (emphasis on allergic) is an inflammatory response to fungal elements in the sinus cavity and is suspected based on certain CT imaging characteristics and physical exam.

Reviewed on 7/14/2014

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