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Sinus Infection (cont.)

How Is a Sinus Infection (Sinusitis) Diagnosed?

The diagnosis of a sinus infection is made based on a medical history assessment and a physical examination. Adequately distinguishing sinusitis from a simple upper respiratory infection or a common cold is important.

  • Sinusitis caused by bacteria usually requires antibiotics for treatment. Sinusitis can also be caused by viruses (meaning antibiotics will not help).
  • Upper respiratory infections and colds are viral illnesses. Treating a viral infection with antibiotics is of no benefit and may cause antibiotic resistance to occur.

CT scan: In most cases, diagnosing acute sinusitis requires no testing. When testing is indicated, a CT scan will clearly depict all of the paranasal sinuses, the nasal passages, and the surrounding structures. A CT scan may indicate a sinus infection if any of the these conditions is present:

  • Air-fluid levels in one or more sinuses
  • Total blockage in one or more sinuses
  • Thickening of the inner lining (mucosa) of the sinuses
  • Mucosal thickening can occur in people without symptoms of sinusitis. CT scan findings must be correlated with a person's symptoms and physical examination findings to diagnose a sinus infection.

Ultrasound: Another noninvasive diagnostic tool is ultrasound. The procedure is fast, reliable, and less expensive than a CT scan, although the results are not as detailed.

If symptoms persist despite adequate therapy, a referral to an otolaryngologist (ENT) may be necessary.

  • The ENT physician can directly visualize the nasal passages and the connection to the sinuses with a nasopharyngoscope, or sino-nasal endoscope. This is a fiberoptic, flexible or rigid tube that is inserted through the nose and enables the doctor to view the passageways and see if the sinuses are open and draining correctly. Anatomical causes of breathing difficulties may also be found, such as a deviated nasal septum, nasal polyps, and enlarged adenoids and tonsils.
  • An ENT specialist may also drain the affected sinus to test for the presence of organisms. This is a more invasive test. During this procedure, a doctor inserts a needle into the sinus through skin (or gum) and bone in an attempt to withdraw fluid, which then can be sent to the lab for culture. Any present bacteria can be identified, often in less than two days. Antibiotics may be given for treatment. If necessary, discomfort is alleviated by local anesthesia. The draining procedure is seldom used, because the CT scan may suffice for the diagnosis of sinusitis, and standard antibiotics are usually effective even when the exact bacterial cause is not known.
Last Reviewed 9/5/2017
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Sinusitis, Acute »

Sinusitis is characterized by inflammation of the lining of the paranasal sinuses.

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