The anatomy structures should only be precoordinated with laterality if they are lateralizable. All anatomy structures on the midline are not lateralizable. The Lateralizable Body Structure Reference Set has been developed and published as part of SNOMED International release. Please note that the refset requires an ongoing update for new additions.
Both Left and Right structures must be added when adding the new precoordinated concepts for anatomy structure with laterality. Lateralization should not be routinely applied to Entire and Part of anatomy concepts unless the concept model requires such lateralized anatomy structure.
Bilateral X anatomical structure (body structure) must not be added. The concepts under 422525002 |Structure of bilateral paired structures (body structure)| are no longer in use in the international edition of SNOMED CT because bilateral concepts are defined by two role groups. However, these concepts may still be in use by extensions, in postcoordinations, or as values in information models. We would recommend users to review their usage and provide feedback to us. Users will be consulted before these concepts are ultimately inactivated.
Following are the most common term patterns for the representation of laterality for anatomy structures. Preferred terms should have the same description without a semantic tag. In descriptions in hierarchies such as clinical finding/disorder, procedure, observable entity, and situation with explicit context, 'structure of' can be omitted when body site is not a concept of Entire anatomy entity.
Structure of left hand (body structure)
Structure of right lung (body structure)
Structure of left ring finger (body structure)
Structure of left renal artery (body structure)
Bone structure of left tibia (body structure)
Structure of right half of head (body structure)
Structure of right cerebral hemisphere (body structure)
Bone structure of left hand (body structure) - bone structure is constitutional part of hand
Bone structure of phalanx of left ring finger (body structure)
Skin structure of right foot (body structure) - skin structure is constitutional part of foot
Skin structure of left index finger (body structure)
Finger/toe is not sufficient - Laterality should be placed before hand/foot when finger/toe or any part of a finger/toe is not further specified to individual digit, e.g., ring finger, index finger, great toe.
Parts of symmetric structures should be symmetric. However, some body parts are exceptions. The laterality value in modeling is inherited from its lateralizable parent concept, e.g. left/right lung structure. Therefore, descriptions must clearly indicate such inheritances to avoid potential confusion. It is not accurate for a term such as "right middle lobe" because there is no "left middle lobe". The following are examples for correct description pattern. Note: existing content has not been following the term pattern.
Leave the new concept as primitive if concept 'Structure of half of Y lateral to mid-sagittal plane (body structure)' does not exist. The new concept for 'Structure of half of Y lateral to midsagittal plane' should not be added until the policy is developed.
The 'part of' relationship should not be used for concept modeling in anatomy. The laterality attribute should be the only attribute for the representation of laterality. The new concept model for anatomy has not been implemented, and the proximal primitive modeling style should not be applied.
For term pattern 1, the concept X or lateral half of Y should be used to fully define a concept with laterality, as shown in these examples:
For term pattern 2, the precoordinated concept {part} of X should be used to fully define the concept with laterality. Note: Concepts for which an identifier has not been assigned have been shown with an identifier of '1111111111'.
For example,
Please note that the concept modeling and utility of precoordinated concepts of 'structure of {part} of lateral half of Y' and 'structure of half of Y lateral to mid-sagittal plane' are still under investigation. Similar new anatomy concepts should not be added. The concept model should only use existing precoordinated concept {part} of lateral half of Y.
For example,
If precoordinated concept does not exist for '{part} of structure of half of Y' or 'structure of half of Y lateral to mid-sagittal plane', the concept can be defined by {part} of Y and the definition status should be primitive.
For example, concept |Structure of lateral half of lower back| does not exist, the concept 'Structure of left half of lower back' should be defined as a primitive concept. Two parent concepts are expected: 61379005 |Structure of left side of trunk (body structure)| and 37822005 |Lower back structure (body structure)|. The additional parent |Structure of left side of trunk (body structure)| is to ensure that any lateralized concept must be a subconcept of a lateralizable structure.
SNOMED CT uses a structure-entire-part triple, known as the SEP triple , to represent anatomical structures. The following Relationships provided a way for the anatomy in CTV3 to be mapped to RT:
The SNOMED CT anatomy hierarchy differentiates classes of entire anatomical entities from classes of parts of entire anatomical entities.
Entire concept : Denotes a class that is instantiated by entire anatomical entities of some kind: entire heart is instantiated by all individual hearts.
Entity Part concept: Denotes a class that is instantiated by all anatomical entities that are a proper part of some entity of a given kind: heart part is instantiated by all entities that are a proper part of some heart, e.g. my mitral valve, your right ventricle, Joe's sinus node. Heart part is not instantiated by any heart.
Entity Structure concept : Subsumes both the related Entire and Part concepts. Consequently, it denotes a class which is instantiated by anything that instantiates either the Entire or the Part. For instance, Heart structure is instantiated by my heart, my mitral valve, your heart, your right ventricle, Joe's sinus node, Joe's heart, etc.
The code named Liver structure in CTV3 is equivalent to Liver structure in the diagram above. Both the CTV3 code for Liver structure and the SNOMED RT code for Liver are interpreted to mean Some or all of the liver. Site attributes (PROCEDURE SITE, FINDING SITE) will usually take the value liver structure rather than entire liver , since typically the site of a liver disorder or procedure on the liver is not necessarily the entire liver.
Adding the Entity Structure codes is a convenience to assist with the logic-based aggregation of references to the entity or its parts. The implication of this view is that the E of the SEP triple is the code that should be regarded as the one that represents the real anatomical entity that is named.
For example, the code for entire liver is the one that should correspond to the code for liver in the Foundational Model of Anatomy (FMA). The subtype hierarchy __ for entire liver fits much better with the FMA hierarchies, and indeed it might be possible to completely reconcile SNOMED’s non-Structure components with FMA anatomy.
A database has been developed that categorizes codes in the physical anatomical entity hierarchy according to their status as S structure, P Part or E Entire, and provides the corresponding S and P code for each E code. This should provide some value to implementers. It can help with navigation, coordination with formal ontologies of anatomy, and selection of codes for postcoordination.
Where there were two concepts with the same name, the SNOMED RT code was to become the S code, and the CTV3 code was to become the E code. There are still instances of unrecognized pairing of the RT-CTV3 S-E pair, where neither codes FSN has been changed according to the naming conventions in this document. When these unmatched pairs are identified, it is our practice to change the FSNs accordingly, and to make the E code have a subtype IS-A link to the S code.
Some S codes do not currently have a corresponding E code subtype, and there was no policy that required that such E codes be created during the merger of SNOMED RT and CTV3. However, it is likely that such a policy will be enforced in the future.
The SEP triple may give the impression that all S codes have exactly two children, one E and one P , with all of the remaining descendants placed under P. Again, in the past this degree of modeling consistency was not always followed. Some codes were purposely made subtypes of the S that are not strictly part of the corresponding E.
For example, perirenal tissue is a kidney structure but not a part of the kidney. It is used to define perirenal abscess so that it is subsumed by renal abscess. While a perirenal abscess is not strictly within the substance of the kidney, it is still considered a kind of renal abscess, and the S anatomy hierarchy is used to support this inference.
This policy has introduced undesirable variation and arbitrariness into the terminology, and future revisions will seek to eliminate these variations. Where a code is needed for a site that is really meant to extend to entities that are not part of any kidney, this will be made clear in the name, e.g. Structure of kidney and perirenal tissue.
The E code needs to be interpreted with care when the x name refers to entities that do not have the property of identity, meaning that they are not countable wholes, or could be interpreted as non-countable. In this circumstance, the interpretation of E means some portion of the thing being named.
For example, tissue and types of tissue such as fascia, muscle, tendon, bone tissue, connective tissue, skin, mucosa/mucous membrane, nerve tissue, etc. Muscle, tendon, bone and skin can identify a type of tissue as well as an individual organ of that type. Bone tissue has no identity, but a particular bone does have identity.
To use skin as the archetypal example, the E code for skin of finger means a portion of the skin of a finger, so all of its subtypes must also be portions of skin. The S code for skin of finger then has a subtype P which would mean proper part of a portion of skin of finger. This admits subtypes that are not kinds of skin, but may be parts of skin, including layers, e.g. epidermis of finger (meaning a portion of epidermis of finger) could be a proper part of a portion of skin of finger.
We regard the E code for x tissue, x layer to have the meaning portion of X tissue , and therefore regional subdivisions of tissue types are direct subtypes.
For example, transitional epithelium of urinary tract, as an E kind of code, should be a supertype of transitional epithelium of urinary bladder. The reason is that (portion of) transitional epithelium of urinary bladder is a kind of (portion of) transitional epithelium of urinary tract.
We also deal with layers the same way.
For example, we regard serosal layer and serosa tissue as meaning the same thing, since all serosal tissue is conifigured as a layer, and it can’t be a serosa without being a layer; and their E codes mean portion of serosal layer or portion of serosal tissue.
As another example, layer of retina would be a supertype of nerve fiber layer of retina, and also a supertype of retinal epithelium, where retinal epithelium represents a portion of the epithelium of the retina and is therefore a kind of (portion of) a layer.
The identity/countability issue extends to a problem differentiating groups of entities from one of the group.
For example, consider x = lymph node group , y = lymph node. In this case, the group should be linked to the member via an appropriate Relationship(not yet in SNOMED CT), such as has-member. In those cases where y is always necessarily a member of group x, it could be linked via a member-of Relationship(also not yet in SNOMED CT).
What does part of mean?
There are several possible ways of interpreting part of. In SNOMED CT, A part of B means that in normal anatomy, the entire structure A is structurally included in B. Another way of saying it is that A is part of B if there is no part of A that is not also part of B.
For example, the humerus is not part of the shoulder region, because the distal humerus is part of the humerus, and the distal humerus is not part of the shoulder region.
We do not use part of for non-anatomical meanings, such as grouping tests together in batteries, nor do we use it to indicate Relationships that are not strict anatomical inclusion.
Some recent work has begun to differentiate between part of that is reflexive (that is, an entity is in some sense a part of itself , much the same that a set can be viewed as a subset of itself), versus proper part of , where an entity cannot be a proper part of itself. For now, we regard part of Relationships as implying strict partonomy.
There is sometimes confusion about parthood as opposed to location.
For example, an embryo is not part of a mother's body, but a kidney is. The anatomy section is composed mainly of canonical parts; but a few abnormal parts are included to permit them to be used as the location of tumors or injuries.
For example, a Meckels diverticulum is a body structure that is part of the small intestine, and it is also a morphological abnormality. Likewise some stomas and other post-surgical structures are considered part of the body. A transplanted liver or kidney would be considered part of the body, as a post-surgical structure, even though the transplanted organ is not genetically identical. Likewise transplanted bone marrow is part of the body.
Non-living implants and devices, and foreign bodies, on the other hand, are considered to be located in the body, but not part of the body.
For more information on part of relationships in the anatomy concept model, please see .
The currently distributed part of Relationships need to be much more extensively modeled and quality assured. At present they are not defining , that is, their Characteristic Type in the relationship file is additional, and, therefore, they do not affect the classifier behavior. A substantial amount of effort has gone into a draft of the updated part of Relationships; these will require review and approval before incorporation into the release. This will eventually result in the SEP triplet structures and part of relations being strictly paralleled. It is a matter of time to implement and quality assure the changes.
The SEP structure, combined with the inference mechanism that is used with SNOMED CT, allows us to take advantage of anatomical Relationships to infer subsumption, IS_A Relationships between disorders, procedures, and other entities without reference to part of Relationships. The SEP structure also permits us to sufficiently define anatomical structures without reference to part of Relationships (making them necessarily true , but not among the necessary and sufficient conditions).
For example, the Structure of left hand can be sufficiently defined as a hand structure with laterality = left. This definition is sufficient. Converting the part of Relationships to have Characteristic Status = defining will require significant changes to the current model.
Points, lines, and surfaces can be considered to be massless. The FMA calls these immaterial. It is important to differentiate the codes/names for these entities from those that are intended to represent entities that have mass. At present, the concepts under anatomical spatial entity represent massless entities. Massless entities are not represented using the SEP model. It is conceivable that users may want to reference parts of a surface, and to enable this we would need to apply the SEP model to anatomical spatial entities, or else adopt defining part of Relationships.
This attribute provides information on whether a body structure is left, right, or bilateral. It is applied only to bilaterally symmetrical body structures which exist on opposite sides of the body.
With the addition of lateralized content in the International Release, the need for unspecified unilateral concepts is removed, as well as potentially dangerous, if used directly in a patient record. Unilateral concepts will not be accepted.
Bone structure of proximal right humerus (body structure) - proximal is regional part of humerus
Bone structure of shaft of left femur (body structure) - shaft is regional part of femur
Lateral half of Y
Y represents any anatomy structure that is symmetrical on the body's middle-line which cannot be lateralized. However, the lateral half of Y can have laterality, e.g. right half of head.
{Part} of X or Y
{Part} represents any constitutional or regional part of anatomical structure of X or lateral half of Y.
Structure of finger of left hand (body structure)
🟢 correct
Structure of left finger (body structure)
🔴 incorrect
Bone structure of phalanx of finger of left hand (body structure)
🟢 correct
Bone structure of phalanx of left finger (body structure)
🔴 incorrect
Structure of nail of toe of right foot (body structure)
🔴 incorrect , neither 'right nail' nor 'right toe' is correct
Note, hand/foot is redundant when an individually named finger, e.g. index finger, or the great toe has been specified in a description. For example,
Bone structure of phalanx of left index finger (body structure)
🟢correct
Bone structure of phalanx of index finger of left hand (body structure)
🟠 it is not wrong, but 'hand' is redundant
Bone structure of phalanx of left index finger of hand (body structure)
🟠 it is not wrong, but 'hand' is redundant
