Anatomy of Anatomical Location

Some time ago I intended to start blogging about clinical modelling insights and conundrums. It hasn’t happened for a while but, with recent reviews and publication of archetypes occurring as part of the openEHR Industry archetype sprint, we have started to make some clear progress.

Anatomical location seems pretty simple at first glance. In terms of scope though, it is huge and complex. In terms of use cases it is ginormous.

As a result of a number of reviews, the Anatomical Location archetype has recently been published – this means that the content is regarded as stable and fit for use in clinical systems. You can find the latest version here on the openEHR CKM.

In a mind map form, the archetype has the following data elements:

2015-06-18_16-02-52

It’s intended use is described as:

Use to record structured and consistent details about a single identified physical site on, or within, the human body.
This archetype is specifically designed to be used within the context of any appropriate ENTRY or CLUSTER archetypes which supply the context of the anatomical location.
As a fundamental part of clinical practice, clinicians can describe anatomical locations in a myriad of complex and variable ways. In practice, some archetypes carry a single data element for carrying a simple description of body site – for example, OBSERVATION.blood_pressure and CLUSTER.symptom when describing ear pain. In this situation, where the value set is predictable and simple to define, this single data element is a very accurate and pragmatic way to record the site in the body and to query at a later date. However in the situation where the anatomical location is not well defined or needs to be determined at run-time, it may be more flexible to use this structured archetype. For example, in the situation where any symptom can be recorded without any predefined scope of the type of symptom, then allowing the use of this archetype to specifically define an anatomical location in the body may be useful. In this case the CLUSTER.symptom archetype also carries a SLOT for ‘Detailed anatomical location’ which can include this archetype to support maximal flexibility in recording anatomical location data.
This archetype supports recording complex structured anatomical sites. For example, the apex beat of the heart is typically found at the fifth left intercostal space in the mid-clavicular line, tenderness at McBurney’s point on the abdominal wall or a laceration on the palmar aspect of the proximal right thumb.
A combination of the data elements in this archetype can be used to individually record each component of a post-coordinated terminology expression that represents the anatomical site.
The ‘Alternative structure’ SLOT allows inclusion of additional archetypes that provide an alternative structure for describing the same body site, such as CLUSTER.anatomical_location_relative or CLUSTER.anatomical_location_clock, should this be required. In the situation where this archetype can only be used to name a large and/or non-specific body part, the additional use of the CLUSTER.anatomical_location_relative archetype will support recording of a more precise location – for example, 2 cm anterior to the cubital fossa of the left forearm or 4 cm below R costal margin on the chest wall in the mid-clavicular line.
If this archetype is used within other archetypes where the specified subject of care is not the individual for whom the record is being created, for example a fetus in-utero, then the anatomical location will be identifying a body site on or within the fetus.

This is a clinical specification identifying a single location on the body, and is never used stand-alone, but nested within other CLUSTER archetypes – for example: CLUSTER.exam_skin to define the area of skin that is being examined, or CLUSTER.symptom to define where the symptom was experienced.

You will also note that this archetype alone may not be enough. We have created the ‘Alternative structure’ SLOT in which other anatomical location archetypes can also be nested, allowing for description of relative anatomical location and also referencing a clock face, typically used to describe the position of haemorrhoids! We anticipate that other CLUSTER archetypes (yet to be developed) will be used for specific situations such as inside the mouth for describing locations for oral medicine/dentistry, where there are unique ways to describe anatomical structures.

I received a question by email recently asking about why we specifically excluded unilateral/bilateral occurrences of an anatomical feature. Remember that this archetype is recording ‘where it was’ not the number of occurrences of a something.

My answer:

An anatomical location for a clinical condition is not usually recorded bilateral (or both sides) in its own right.  For example, something might have bilateral occurrence AND be located in the cubital fossa but it will not be recorded in the health record as located in the “bilateral cubital fossae”.

When we talk we often have to qualify a statement made about a bilateral ‘something’ as it is not exactly the same on both sides, and we probably wouldn’t record it as we say it, but record the subtleties of each side separately.

Do they bilateral anatomical sites or body locations exist? Yes, there are 42 results when searching for ‘bilateral’ in SNOMED CT body structures – bilateral lens, bilateral ears, bilateral eyes, bilateral breasts etc. But do clinicians refer to a lesion in the bilateral lens, ears, eyes or breasts – not in my experience!

Similarly, there are 136 results when searching for ‘both’ in SNOMED CT body structures – both legs, both eyes, both ears, both feet etc. We are still not likely to refer to a lesion in both breasts, rather describe each lesion in separate locations within one breast and then separately describe them in the other breast.

A rash could be on left & right (i.e. both) wrists. We may talk about a bilateral rash on the wrist but this is not usually recorded in data as a rash on ‘bilateral wrists’, rather a rash with a common morphology present to ‘x’ extent on the right wrist and to ‘y’ extent on the left wrist! In a similar way,  recording the rash observed on both wrists, shoulders, elbows and ankles really needs the ability to record each site and extent specifically.

An injury to the ankles might be bilateral but the site of the injury will not usually be recorded as “bilateral ankles” – the injuries on each ankle need to be described individually as the location might be lateral ligament on one and medial on the other. And further, even if it were lateral ligament damage for both, it would be weird to describe the location as bilateral lateral ligament of the ankle or, worse, lateral ligaments of bilateral ankles.

This reasoning is why ‘bilateral’ is specifically excluded from anatomical location and the scope of the archetype is restricted to a single site in a single archetype instance.

Most commonly when we use the term bilateral, we refer to bilateral conditions – for example “bilateral hemiplegia, worse on the right”. A diagnosis. This could be the diagnosis value recorded against the ‘Diagnosis name’ data element in the Problem/Diagnosis archetype but the more accurate recording will again be Hemiplegia on the left has ‘x’ attributes and Hemiplegia on the right side of the body has ‘y’ attributes. They occur as a result of different events and the effect on the body will not be mirrored.

Hearing problems could be experienced in both ears – the value set for the ‘Ear examined’ could be left ear, right ear and both ears, but again, I’m not convinced that this is good history taking. However, testing for hearing may validly have the value sets for ‘ear examined’ as left ear, right ear and bilateral as this reflects how the test was conducted  – specifically where the earphone or headset would be delivering the stimulus. Bilateral testing in a sound field is common in young kids and as a consequence the results for each ear cannot be differentiated  – a valid use for bilateral, even bilateral ears, although ears is somewhat redundant under the circumstances.

Thoughts?

It is not simple. We need to carefully identify where we need to record ‘bilateral’ and ensure that this is accurate.

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