What is the role of lab studies in the workup of otitis externa (OE) and what are the histologic findings?

Updated: Mar 09, 2020
  • Author: Ariel A Waitzman, MD, FRCSC; Chief Editor: Ravindhra G Elluru, MD, PhD  more...
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The patient’s history and physical examination usually provide sufficient information to allow the clinician to make the diagnosis of otitis externa (OE). Most persons with OE are treated empirically.

Thus, laboratory studies typically are not needed. However, Gram staining and culture of any discharge from the auditory canal may be helpful if the patient is immunocompromised, if the usual treatment measures are ineffective, or if a fungal cause is suspected. However, as many as 40% of all cases of OE do not produce a dominant pathogen. Adults with OE may benefit from a blood glucose check or a urine dipstick test to evaluate for occult diabetes.

Histologic examination of the skin of the external canal shows acute inflammation with exudate.

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