Otitis Externa 

 

Although clinicians often use the term otitis externa (OE) loosely to mean ear infection these are two different conditions.  Otitis externa is an inflammation of the external ear canal.  It is not a final diagnosis, but rather a clinical finding. Infection is often present with otitis externa, but is rarely the true cause of the inflammation.

 

Otitis externa is especially common in cocker spaniels and dogs with pendulous ears.  This condition is also reported in cats, but less frequently. 

 

The most common primary causes of OE are:

 

·        Hypersensitivity disorders (such as atopy, contact allergy and adverse food reactions)

·        Foreign body, trauma

·        Parasites (ear mites are most common cause in cats)

·        Keratinization defects

·        Neoplasia and masses

 

Certain conditions are thought to contribute to, but not directly cause, OE, such as:

 

·        Increased moisture in the ear canal

·        Increased cerumen production

·        Immunocompromized status of patient

·        Inappropriate ear cleaning

 

 

            Bacteria and fungi are usually Not a primary cause of OE but rather the result of the primary inflammatory process.   Normal flora in the ear canal includes staphylococcus and malassezia.  Inflammatory changes lead to overproliferation and establishment of infection. Care should be taken in reading microbiology results to ensure that what is reported is actually an overabundance rather than the normal amounts of flora for that species.

 

Otitis externa will not resolve until the underlying disease process is treated and the perpetuating factors (i.e., bacteria, yeast, stenosis, fibrosis, etc.) are controlled.

 

Interesting facts!  

 

1.            Cerumen (ear wax) is important for several reasons:

 

·        Traps debris and microorganisms so they can migrate their way out of the ear canal

·        Contains immunoglobulins important for immunity

·        Provides moisture for the tympanic membrane, which helps keep it pliable.

 

2.            Pathogenesis of ear infection in dogs and cats is different than in humans.  In

humans it is normally an ascending infection from the pharynx to the Eustachian tube to the middle ear.  Whereas in dogs, they become infected via the external canal first and then may rupture into the middle ear.

 

Coding Otitis Externa and Ear Infection using SNOMED CT

 

If the clinician writes ONLY otitis externa:

 

            Code the disorder concept, Otitis externa (disorder) 3135009  DA-91210.

 

            Note:  This is a pre-coordinated concept and already includes in its hierarchy “ear structure”.  Thus, adding a finding site of ear structure would be redundant.  However, the otitis externa concept may be further defined by using laterality (left, right or bilateral).

 

            Example 1:       Otitis externa (disorder) 3135009  DA-91210

                                                With laterality (attribute) 78615007  G-C220

                                                            Right (qualifier value) 24028007  G-A100

 

 

 

When coding for bacteria, yeast, or other microorganisms, note that the bacteria or yeast are descriptive terms for the OE (i.e., there is a pneumonia, and bacterial pneumonia vs. fungal pneumonia).  When coding an OE, and the microbiology report shows abnormal growth of a microorganism, the appropriate microorganism concept may be linked to the chosen disorder concept.

 

Coding can be captured in several ways depending upon the clinician’s documentation in the record. 

 

If the clinician clearly means otitis externa with secondary bacterial infection (whether written explicitly or established with the medical records department by convention), here is how it may be coded:

 

Example 2:       1) Otitis externa (disorder) 3135009 DA-91210

                        and

2) Secondary infection (disorder) 264569006  DE-000C0

       Causative agent (attribute)  246075003  G-C17D

Bacterium (organism)  41146007  L-10000

                Finding site (attribute) 363698007 G-C0E3

      Ear structure (body structure)  117590005  T-AB001

 

                                   

If the clinician intends “(primary) bacterial otitis externa” as the diagnosis in the case, OR, if there is no clear convention it may be coded as follows:

 

Example 3:            Otitis externa (disorder)  3135009  DA-91210

                                                Causative agent (attribute)  246075003  G-C17D

Bacterium (organism)  41146007  L-10000

 

If the diagnosis is written as ONLY ear infection, and there is no clear convention, it is recommended that the coder ask for further clarification as to it’s intended meaning.

 

Data Retrieval

 

Any of the 3 methods of coding above will capture “otitis externa” or “disorder of ear” in a retrieval.  The case in example 1 will not be retrieved using a search for “infection” unless the search also asks for otitis externa (which is an inflammation, not an infection) in conjunction with ear infection.   Thus, when searching for otitis or ear infection cases, it would be wise to search for both. 

 

An additional problem occurs if a search is done Specifically for “disease of right ear (example 1).  Systems must be sophisticated enough to know that ear structure is part of the definition of otitis externa, as the laterality must be applied to the anatomical structure NOT to the disorder if such a retrieval is to be successful.

 

 

By Kathy Ellis, 11/01/01

Thanks to Dr. John Angus, U of Illinois, Dr. Jeff Wilcke, Virginia Tech and Bobbi Schmidt, Ohio State for their assistance.   Also referenced  “Ear Disease of the Dog and Cat, by Harvey, Harari, and Delauche, IA State University Press, 2001”.