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SNOMED CT Hierarchy & Structure

As mentioned in a previous tip of the month, SNOMED CT is not merely a large list of encoded medical terms. 

Its structure, hierarchy and relationships are significant in the definition and use of concepts. We often see duplicate terms in different hierarchies which can be confusing when implementing SNOMED CT (Figure 1). 


Abscess 44132006 Morphologic Abnormality
Abscess 128477000 Disorder
Wound 13924000 Morphologic Abnormality
Wound 416462003 Disorder
Wound Finding 225552003 Finding

               Figure 1: SNOMED CT Concepts in Different Hierarchies


Here are some tips when implementing these SNOMED CT terminology domains to facilitate semantic interoperability and secondary data use:

  • Body Structure is the high level domain that includes all (Morphologic Abnormality) concepts
  • Clinical Finding is the high level domain that includes all (Disorder) concepts

Morphologic Abnormalities are used to define the body location of the Finding or Disorder concepts. They are the ATTRIBUTES for the Clinical Findings hierarchy. Therefore, both Wound Finding (Finding)|225552003 AND Wound (Disorder)|416462003 have  ‘ASSOCIATED MORPHOLOGY’ Wound (Morphologic Abnormality) | 13924000. Remember morphologic abnormalities should never be used to populate a problems list or encode clinician observations.

It is recognized across the industry (as well as by SNOMED International) that it is often a challenge to differentiate between findings, disorders, events or situations.  However, there are some key differences between Finding and Disorder:

  • Disorders are always abnormal with an underlying pathological process
  • Disorders are manifested as findings
  • Findings can exist at a single point in time and depend on the observer (often times clinician) who is observing them (e.g. Normal Breath Sounds )

These simple take-aways can help you in remembering that concept meaning matters when mapping and implementing terminologies. We map SNOMED CT and offer services when implementing terminologies. Contact Us!