The 123037004 |Body structure (body structure)| subhierarchy includes both anatomical structures and morphologic abnormalities

The body structure domain includes anatomical structures, as well as morphologic abnormalities, as follows:

• Body structure (body structure)

  • Anatomical or acquired body structure (body structure)

  • Anatomical organizational pattern (body structure)

When authoring in this domain, these are the approved attributes and allowable ranges.

See also the respective .

This section contains naming conventions for anatomical structures in SNOMED CT.

SNOMED CT is arranged as a polyhierarchy. A hierarchy is defined as an ordered organization of concept codes linked together through IS A relationships. Concept codes are linked to their more general parent concept codes directly above them in a hierarchy. Concepts with more general meanings are usually located at the top of the hierarchy and then at each level down the hierarchy the meanings become increasingly more specialized.

Selected SNOMED CT attributes have a hierarchical relationship to one another known as attribute hierarchies. In an attribute hierarchy, one general attribute is the parent of one or more specific subtypes of that attribute. Concepts defined using the more general attribute can inherit concepts modeled with the more specialized subtypes of that attribute.

The following are the 19 domains arranged in alphabetical order.

There are two types of abscesses:

1. septic

2. sterile

Most abscesses are septic, which means that they are the result of an infection.

If a concept's meaning, based on its FSN and text definition, does not specify whether the abscess is sterile or septic, then the concept should not be modeled as septic.

The ear includes the external, middle and inner ear. The external ear has two main parts, the auricle (also called the pinna) and the 84301002 |External auditory canal structure (body structure)|.

The external auditory canal has the synonym external auditory meatus. The external auditory meatus is not just the external opening of the canal, but rather the canal extending to the ear drum ( 42859004 |Tympanic membrane structure (body structure)|).

The 61671002 |Structure of internal acoustic meatus of temporal bone (body structure)| (SYN, internal auditory canal, is not part of the ear. As described in the FSN, it is an opening in the temporal bone, and is primarily a nerve conduit that anatomically parallel to the external auditory canal.

Provide Feedback

The endocrine system is composed of the endocrine pancreas, pineal body, paraganglia, paraaortic bodies, parathyroid glands, endocrine ovaries, endocrine testes, adrenal glands, pituitary gland, thyroid gland, juxtaglomerular apparatus of the kidneys, and some diffuse neuroendocrine structures. Certain parts of the thymus produce endocrine hormones, but the thymus itself is not part of the endocrine system.

Provide Feedback

Distinguishing consistently between lump and mass can be difficult in diagnostic contexts, as the terms are often used interchangeably or lack precise definitions. As a result, lump and mass have, in certain conditions, been treated as synonymous.

Avoid using 'lump' in new content, where more specific terminology is available.

Lump should not be added as a synonym for mass concepts in the Finding or Disorder hierarchies. Existing legacy synonyms and concepts will remain unchanged.

Provide Feedback

Death is an event, not a disorder.

Sudden cardiac death

Sudden cardiac death is a term used in clinical practice. It refers to an arrhythmia that results in sudden loss of cardiac function which, if not quickly reversed, will lead to actual death. The FSN Sudden cardiac death (disorder) is modeled as a subtype of 127337006 |Acute heart disease (disorder)|. It should not be classified as death. Individuals with sudden cardiac death have not necessarily been declared dead and are frequently revived. It is regarded as a subtype of cardiac dysrhythmia.

Provide Feedback

1. FSN must include the word 'structure', 'entire' or 'part' for concepts that are following the SEP model.

For example,

• Liver structure (body structure)

• Entire liver (body structure)

• Liver part (body structure)

For example,

For example,

S concepts are usually named x structure (body structure) or structure of x (body structure). E concepts are usually named entire x (body structure) or x entire (body structure). P concepts are usually named x part (body structure) or part of x (body structure).

Modeling of cells expressing antigens

As the cell hierarchy is primitive, careful attention is needed to manually identify and add the appropriate supertypes.

Undifferentiated cell concepts with a single positive or negative antigen expression (e.g. cell vs. lymphocyte or blast) are immediate subtypes of 362837007 |Entire cell (cell)|.

• For example,

  • 725316009 |Cell positive for CD1 antigen (cell)| Is a 362837007 |Entire cell (cell)|

Undifferentiated cell concepts with multiple positive or negative antigen expressions should be subtypes of the appropriate cell concepts with those same single and combinations of positive/negative antigen expressions.

Differentiated cells concepts with positive or negative antigen expression(s) should be subtypes of both: a) the differentiated cell concept of differentiation; and b) the appropriate undifferentiated cell concept with the appropriate positive or negative antigen expression(s).

• For example,

  • 117507002 |FMC7+ lymphocyte (cell)| should be a descendant of 56972008 |Lymphocyte (cell)| and also 1373072009 |Cell positive for FMC7 antigen (cell)|.

Choroid

Both subchoroidal and suprachoroidal refer to the same potential anatomic space between the choroid and the sclera. The term lamina subchoroidea of choroid is the same as the lamina suprachoroidea.

Retinal vein

There is not a vein actually named retinal vein. However, SNOMED CT has concepts with the phrase.

For example,

• 85003000 |Structure of retinal vein (body structure)| has the synonym retinal vein.

  • 280927000 |Entire central vein of the retina (body structure)| has the synonym entire central retinal vein.

371398005 |Eye region structure (body structure)| has a synonym of orbital region structure which subsumes bony orbit, entire eye, and ocular adnexa.

When modeling a concept requiring two role groups with the same finding site/body structure but two different morphologies (because a combined morphology does not exist), then those two morphologic abnormalities can be combined to create a new single, combined |(morphologic abnormality)| concept. Keep the newly created morphologic abnormality concept primitive as all morphologic abnormality concepts should be primitive. Limit the combination to two morphological concepts into a single concept; combining more than two morphological concepts into a single combined concept is not permitted.

Example, If 400067002 |Acantholytic epidermal nevus (disorder)| had the same Finding site of |Skin structure (body structure)| with two different morphologic abnormalities of |Epidermal nevus (morphologic abnormality)| and |Acantholysis (morphologic abnormality)|, then those two morphologic abnormality concepts can be combined to create a single, primitive, morphologic abnormality concept of |Acantholytic epidermal nevus (morphologic abnormality)|. This will prevent modeling with two relationship groups.

Instead of modeling as per this diagram in the stated view with two morphologies of the same finding site:

Model as in the stated view of this diagram with a combined morphology:

Morphologies can be combined to create a single morphologic abnormality concept where doing so creates a specialization of the morphology e.g. 55075001 |Bleeding ulcer (morphologic abnormality)|. Where morphologies are different e.g. abscess and cellulitis, they can not be combined.

Combining morphologies to create a specialization is done when modeling a concept that requires two role groups with the same body structure and two morphology values. Creating a combined morphology concept enables one role group to be used.

Subtypes of 108369006 |Neoplasm (morphologic abnormality)| are not to be combined. These morphologies represent histological cell types that are recognized internationally by pathologists, classified by WHO, and aligned with the ICD-O classification.

Disorders which involve congenital anomalies are defined with:

• Occurrence (attribute) = Congenital (qualifier value)

• Associated morphology (attribute) = Morphologically abnormal structure (morphologic abnormality)

• Pathological process (attribute) = Pathological development process (qualifier value)

Therefore, congenital does not need to be represented as the Associated morphology (attribute) target value. Congenital anomaly morphology concepts usually have non-congenital parents.

When considering the creation of a new morphological abnormality concept, consider the following:

• When the name of a potentially new morphology is the same as the disease, creation of that new morphologic abnormality concept may not be beneficial since it would not be very morphologically descriptive.

• Determine if there is benefit in creating a new morphology for a very small number of rarely used leaf nodes. If the new morphology is needed to differentiate two non-leaf concepts, that would be sufficient to create the new morphology. Otherwise, use the nearest existing morphologic abnormality.

• Including a body site in a morphological abnormality concept is forbidden unless there is a clear modeling and pathological need.

Concepts from the Morphologic Abnormality hierarchy should not be used in place of concepts from the Clinical Findings hierarchy, even though they appear to refer to similar clinical situations.

• For example

  • 4147007 | Mass (morphologic abnormality)| is not a finding, but 300848003 | Mass of body structure (finding)| is a finding

Morphologies are used as the values of the defining attributes of findings and procedures. Findings are used to represent the combination of a morphology and a location.

• For example

  • 300923002 | Cyst of scalp (disorder)| represents cystic type of morphology that has the location, scalp

Many morphologies have names that could be misinterpreted as implying a process rather than a structure.

Inflammation might mean the structural-morphologic features of inflammation, such as inflammatory cell infiltrates; or it might mean the process that causes the structural changes. Within the morphologic abnormality hierarchy, the structural interpretation is intended, not the process interpretation.

A disorder is always and necessarily an abnormal clinical state.

Disorder modeling information is as follows:

• Specific Clinical finding and Disorder Modeling

• Disorder Combination Modeling

Cardiologists noted confusion in the placement of Conduction disorder of the heart (disorder) as a broad grouping that subsumed arrhythmias and heart blocks. In common usage arrhythmia refers to a broad set of conditions that include conduction disorders, under which are heart blocks. The concept Cardiac arrhythmia (disorder) is a parent of Conduction disorder of the heart (disorder), and the active referent of the inactive concepts named dysrhythmia or arrhythmia.

For example,

• Arrhythmias, like 72654001 |Supraventricular arrhythmia (disorder)|, are under 698247007 |Cardiac arrhythmia (disorder)|

Conduction disorders include heart block, AV block, bundle branch block, conduction delay, and conduction defect, like 418341009 | Atrioventricular conduction disorder (disorder) |. Other arrhythmias were moved from under 44808001 |Conduction disorder of the heart (disorder)| and placed under 698247007 |Cardiac arrhythmia (disorder)|.

The term enteritis is broad and commonly refers to inflammation of the intestine, especially the small intestine. However, in some conditions, e.g. phlegmonous enteritis and regional enteritis, the term enteritis refers to any part of the digestive tract.

Thus, all descriptions of enteritis must stipulate the specific body structure that is affected to avoid potential misinterpretations and incorrect modeling.

For example,

• Enteritis of intestine

• Enteritis of small intestine

Order antigens numerically first.

• For example,

  • 732279009 |Cell positive for CD3 antigen and positive for CD4 antigen (cell)|

Many terms that refer to body systems or tracts are used imprecisely in clinical practice and in medical publications. Ambiguities frequently arise with many of these terms. We have made the following definitions and distinctions in order to achieve internal consistency of the terminology. We recognize that it may not be possible to get universal consensus for the names for each of these concepts. The goal is to be consistent and clear in defining the meaning of each concept and to allow users and system designers to present the terms that best reflect these meanings in their own implementations.

The genitourinary system includes the entire urinary system, as well as the genital system. The genital system includes internal genital organs and external genitalia.

The urinary system includes the organs that form and excrete urine, the kidneys, ureters, bladder, and urethra. The male urinary system includes the prostatic urethra (since it is a male urinary outflow structure).

In common usage, urinary system and urinary tract are used interchangeably. However, in SNOMED CT, this is not they case, i.e., they are not synonyms. The two concepts are: 122489005 |Urinary system structure (body structure)| and 431938005 |Structure of urinary tract proper (body structure)|.

The urinary tract proper includes the organs involved in the excretion of urine including the renal pelvis (but not the rest of the kidney), ureters, bladder, and urethra. It is used for disorders affecting the flow of urine (as opposed to its formation) or the urothelium, the lining of the urinary tract.

For example,

Human genes are represented as cell structures (subcellular structures) within the Body structure hierarchy. This reflects the biological reality of genes as physical, organized, functional units within chromosomes.

This approach is consistent with the Foundational Model of Anatomy, the Sequence Ontology, and the HUGO Gene Nomenclature Committee's (HGNC) defining characteristic of chromosomal location. It enables participation of gene concepts in the full SNOMED CT concept model, including hierarchical classification, relationship-based definitions, and use with existing attributes such as FINDING SITE and INHERES IN.

Genes are named according to the HUGO Gene Nomenclature Committee (HGNC).

• FSN: <HGNC Approved Name> gene (cell structure)

This is an example of a body structure that is used to group related terms.

The concept 707861009 |Structure of skin and/or skin-associated mucous membrane (body structure)| intentionally employs disjunction (inclusive Or). It includes structures in the deep layers, but excludes non-skin mucosal epithelium, e.g., bronchial, gastrointestinal, and genitourinary sites of squamous cell neoplasms. The 400199006 |Structure of skin and/or surface epithelium (body structure)| concept is used to represent the sites of these neoplasms.

Skin and/or skin-associated mucosa is intended for use in dermatology. It is not intended to subsume all mucosal structures, which are under Mucous membrane structure (body structure).

Since the phrase skin of finger can mean some or all of the skin of finger (if interpreted as a structure, rather than entire in the The StructureEntirePart (SEP) model , we could use IS-A to represent the relationship between skin of finger and skin of hand. Thus, skin of finger IS-A skin of hand, IS-A

Set of structures through which lymph flows. It includes 59441001 | Structure of lymph node (body structure) | and 83555006 | Structure of lymphatic vessel (body structure) |. It supports the categorization of findings, disorders and procedures that relate to the flow of lymph.

Set of structures with groups of lymphoid cells, including those in the intestines, marrow, liver, and other locations, and the lymph nodes, spleen, thymus, and tonsils and adenoids; excludes the lymph vessels. It supports categorization of lymphomas.

All of the lymphoid system, as well as the mononuclear phagocytic system; the immune system also includes cellular and sub-cellular components involved in cellular and humoral immunity.

Collection of true macrophages, distributed widely in the body (splenic and lymphoid sinusoids, liver Kuppfer cells, pulmonary alveolar macrophages, osteoclasts, macrophages in serous membranes, and microgliocytes); also endothelial cells that line hematopoietic tissues.

Collection of antigen-presenting cells, including the following: epidermal Langerhans, dendritic reticulum, and interdigitating. Class I histiocytoses (Langerhans cell histiocytosis) are disorders of the dendritic cell system.

321667001 |Respiratory tract structure (body structure)|. In SNOMED CT, respiratory tract has the same meaning as the Nomina Anatomica term apparatus respiratorius , which includes the structures through which air passes from the nares to the alveoli. The oral cavity is not included. In common usage, respiratory system may have the same meaning as respiratory tract ; but not in SNOMED CT. Respiratory system does not mean the global respiratory system that might include the CNS components of breathing. Pleura are part of the lower respiratory system, but not a part of the lower respiratory tract.

This phrase has several meanings. The SNOMED CT concepts 119253004 |Upper aerodigestive tract structure (body structure)| and 361922007 |Entire upper aerodigestive tract (body structure)| have the meaning based on the following reference: Cancers of the upper aerodigestive tract constitute approximately 4% of all malignancies. These include cancer of the lip, tongue, major salivary glands, gums and adjacent oral cavity tissues, floor of the mouth, tonsils, oropharynx, nasopharynx, hypopharynx and other oral regions, nasal cavity, accessory sinuses, middle ear, and larynx (Upper aerodigestive tract cancers, Cancer 1995 Jan 1;75 (1 Suppl): 147-53). This definition matches the tumors included in the CAP Cancer Checklist for upper aerodigestive tumors. The esophagus, or at least the cervical esophagus, may be included, but not in SNOMED CT .

The morphologic abnormality subhierarchy is located two levels below the Body structure hierarchy with siblings Apoptosis and Structure resulting from tissue repair process:

• SNOMED CT concept

  • Body structure (body structure)

Multiple x morphologies, such as 125291005 |Multiple cysts (morphologic abnormality)|, are currently subtypes of the “X” morphology. The “X” morphology concept represents a class rather than a singular instance, and this arrangement follows the open world assumption of the description logic in SNOMED CT.

• For example,

  • Cyst of upper eyelid does not mean a single cyst on a single upper eyelid. It represents a class of cyst condition that at least appeared in an upper eyelid. This class would also include a cyst condition involving both upper and lower eyelids.

SNOMED CT accepts tumor concepts, as long as they are included in the International Classification of Diseases for Oncology (ICD-O). ICD-O has two coding systems for coding the site (topography) and the histology (morphology) of the neoplasm:

• Topographical - Anatomical site of origin or the organ system

• Morphological - Tumor cell type or histology and behavior, i.e. malignant versus benign

The topography code describes the site of origin of the neoplasms. The morphology code describes the cell type of the tumor and its biologic activity, in other words, the characteristics of the tumor itself. The morphology code, combined with the appropriate topography, expresses the complete morphological assessment as stated by the pathologist.

When modeling a concept requiring two role groups with the same body structure but two different morphologies (because a combined morphology does not exist), then those morphologic abnormalities can be combined to create a single morphologic abnormality concept. Keep the newly-created morphologic abnormality concept primitive, as all morphologic abnormality concepts are primitive.

For example

For those concepts that describe a congenital anomaly that has been repaired and subsequently acquired an abnormality, follow the naming convention of |Acquired abnormality of X following repair of congenital X (disorder)|.

• For example,

  • 871598001 |Acquired abnormality of common arterial trunk following repair of truncus arteriosus (disorder)|

Provide Feedback

Fully specified names and preferred names should use proper names of digits of hand and foot. The names by order of digits can be added as optional synonyms. The order of fingers is different from the order of digits of hand because the thumb is not a finger in SNOMED CT. Therefore, the order of the finger should not be used to avoid potential confusion.

Naming convention for the structure of digits of hand

The nervous system has two parts, central and peripheral.

• The central nervous system, sometimes also called the neuraxis , consists of the brain and spinal cord. The pyramidal system is a subdivision of the central nervous system; the extrapyramidal system is part of the brain.

• The peripheral nervous system includes all neural structures outside the central nervous system.

The nervous system is also divided as: autonomic, somatic, and enteric.

• The autonomic system is further divided as sympathetic and parasympathetic. The autonomic system is not entirely a part of the peripheral nervous system, but the autonomic nerves are peripheral.

The word nerve has multiple meanings according to the FMA:

• nerve trunk

• neural organ (trunk plus branches, excluding nuclei, ganglia, and roots)

• neural tree organ, including nuclei, ganglia, roots, etc.

A neural tree organ is defined in FMA as a nonparenchymatous organ which has as its parts an aggregate of neurons (nuclei or ganglia) and their axons which are grouped into fasciculi by connective tissue to form elongated, cable-like structures that are arranged into a tree. A nerve , according to FMA, is defined as a segment of a neural tree organ which has as its parts a nerve trunk and its branches; together with other nerves of the same tree, it constitutes a neural tree. The neural tree structure includes:

• Cranial nerve

  • Complex cranial nerve-tract

• Spinal nerve

Nerve , conventionally has two meanings:

• An anatomically distinct nerve trunk (without branches) that is identified in a dissection (e.g. the structure that student identifies when a pin is placed in the trunk of the vagus nerve, for instance located on the arch of the aorta)

• A larger anatomical entity which supports a related set of functions (e.g. all anatomical components of the vagus nerve that are necessary for it to execute its functions (e.g. when a student is asked which nerve is responsible for slowing the heart the answer, the vagus nerve , includes the vagal nucleus, as well as the trunk and branches of the vagus).

• Neural tree designates the second concept in order to distingiush it from the first which is only a part (subdivision of) the vagal neural tree.

A third meaning of nerve, defined by the FMA is: Segment of neural tree organ which has as its parts a nerve trunk and its branches; together with other nerves of the same tree it constitutes a neural tree.

• For example,

  • Chorda tympani, digastric branch of facial nerve, greater petrosal nerve, posterior cutaneous branch of posterior ramus of cervical nerve, superior lateral cutaneous nerve of arm.

  • If one severs the facial nerve, the meaning refers to the trunk. But if one has facial nerve palsy, the meaning refers to the entire distribution of the nerve and the functions served by it.

Cerebrum may refer to the supratentorial brain, which is everything except the midbrain, medulla, pons, and cerebellum. In this interpretation, the telencephalon and diencephalon are in the cerebrum. On the other hand, cerebrum may only refer to the parts derived embryologically from the telencephalon, the cerebral hemispheres and the intercerebral commissure (corpus callosum and anterior commissure).

Supratentorial brain may be used for categorizing tumors and for designating the location of swelling that can result in herniation. The telencephalon and diencephalon (including thalamus, geniculate bodies, pineal body, habenulae, and hypothalamus) are definitely supratentorial. The upper part of the midbrain (mesencephalon) is also supratentorial. SNOMED CT excludes all midbrain structures from the supratentorial brain.

Clinical findings or observations are the active acquisition of subjective or objective information from a primary source. This includes information acquired from human observers, through recording of data via the use of scientific instruments, or indirectly from samples taken from the source, and evaluated separately.

The default context for a Clinical finding concept is:

• Present (vs. being absent)

• Subject of the record (the patient)

• Current, if not specifically stated or specified to a time in the past by an entity linked to the concept

The Clinical finding hierarchy contains the subhierarchy of Disorder. Concepts that are descendants of Disease (disorder) are always and necessarily abnormal clinical states. The Disease subtype allows diseases to be subtypes of other disorders, as well as subtypes of findings.

Concepts with a semantic tag of disorder , must have a parent of Disease (disorder) or subtype of Disease (disorder).

• For example,

  • 95617006 | Neonatal cyanosis (disorder)| has the parent, Disease (disorder). Neonatal cyanosis is also a subtype of 3415004 | Cyanosis (finding)|

The distinction between a disorder and a finding may be difficult to define. There are, however, distinct characteristics of each.

In some cases the disease process is irrefutable, e.g., meningococcal meningitis. In others an underlying disease process is assumed based on the temporal and causal association of the disorder and its manifestation, e.g., nystagmus (disorder) is different from nystagmus present (finding). Nystagmus present (finding) may be a normal physiological response to head rotation. A person who spins around and has nystagmus present (finding), does not have nystagmus (disorder). Alternatively, a person may have nystagmus (disorder), but not nystagmus present (finding), i.e., they do not currently manifest nystagmus. Similarly, hearing loss (disorder) is different from perception of hearing loss (finding), which can be due to a number of temporary causes, such as excessive ear wax.

In modeling some bacterial disorders, there will be situations where either the organism or the toxin (substance), or both values, are required for the causative agent attribute. The decision is often determined by whether or not the bacteria are considered endotoxins or exotoxins. The most common exotoxins are:

• Botulinum Toxin

  • Enterotoxin

  • Cholera Toxin

  • Diphtheria Toxin

  • Tetanospasmin

Exotoxins are more lethal in comparison to endotoxins, but there are vaccines against many exotoxins whereas there are no vaccines against endotoxins. There can be instances where an infection is present but the disease-causing toxins are not; in this case, model the concept only with the organism and not the toxin substance.

Example,

• 276202003 |Infection caused by Clostridium tetani (disorder)| is modeled with a causative agent of 30917009 |Clostridium tetani (organism)| only.

In the situation where a disease is caused by both the infection and the associated toxin, model with both the causative agent and the toxin substance.

Example,

• 76902006 |Tetanus (disorder)| is modeled with a causative agent of 30917009 |Clostridium tetani (organism)| as well as 26159005 |Clostridium tetani toxin (substance)|.

Fractures should be agnostic as to whether they are pathologic or not, unless specified in the FSN or could only be caused by trauma (e.g. open fractures). Although most fractures are traumatic, there are some pathological fractures. Based on its FSN and text definition, if the word pathological is present, use Pathologic fracture (morphologic abnormality).

Example: Modeling Traumatic vs. Pathological Fractures

The Property (qualifier value) hierarchy contains the following:

• 118538004 |Mass, a measure of quantity of matter (property) (qualifier value)|

• 726527001 |Weight (property) (qualifier value)|

Very rarely is the physics definition of weight used. When the term weight is used, it is most often referring to mass , as further demonstrated by the units of measure i.e., grams, kilograms, etc. Unless units specific to the physics definition of weight are specified using Newtons, assume that mass is implied.

To summarize, always use the mass qualifier value unless a concept is requested with Newton units that specifically refer to weight.

Naming conventions for the fully specified name (FSN) for observable entities and for naming evaluation procedures or observable entities that are submitted with names from the IFCC-IUPAC NPU systems are as follows:

General naming pattern: Property, Component, Direct Site

• First: Property

  • Property (the property type of the observable) is named first, when possible.

The terms 'spine' and 'vertebral column' in descriptions of conditions or procedures are often used loosely in clinical discourse but can relate to three different general anatomical concepts:

421060004 |Structure of vertebral column (body structure)| (synonym: Spinal column, ‘Backbone’, Spine)

• includes the bones of the spine and associated joints and ligaments

289959001 |Musculoskeletal structure of spine (body structure)|

• includes the vertebral column plus muscles and tendons associated with the spine

1141981001 |Structure of vertebral column region (body structure)|

• includes the musculoskeletal structure of spine plus spinal canal, meninges, spinal cord, roots and ganglia and immediate soft tissue including adjacent vascular structures where specified.

The last concept has been allocated the following definition: This volume includes the spinal column, its spaces and contents, notably the spinal canal, spinal meninges and spinal cord. It also includes the muscles associated with the spine within (and including) the anterior and posterior thoracolumbar fascia and its equivalent nuchal fascia in the neck. This region also includes the spinal ventral (anterior) and dorsal (posterior) roots, the dorsal root (spinal) ganglions and the spinal nerve trunks.

To emphasize the different volumes, cross-sections are shown below of (Figure 1) the vertebral column in yellow, and (Figure 2) the larger vertebral column region in amber color.

From the preceding descriptions, it is clear that Vertebral column region is a broader concept for 'spine', and it should be used when a procedure or condition could involve not only the bony component of the vertebral column, but also the spinal cord, nerve root, muscle, bone, or joint of spine.

For example,

• MRI of thoracic spine (procedure) is modeled with 1141986006 |Structure of thoracic vertebral column region (body structure)|.

• Pain in sacrum (finding) is interpreted as being related to the more general notion of 1144746008 |Structure of sacral vertebral column region (body structure)|.

When a procedure or disorder is exclusively related to musculoskeletal structures of the spine, the 'musculoskeletal structure of spine' should be used.

For example,

• Cervical traction (procedure), Manipulation of the cervical spine (procedure), and Rotational deformity of cervical spine (finding) are all modeled with 297166009 |Structure of musculoskeletal system of cervical spine (body structure)|.

Where a procedure or condition only effects the bone, joint, or ligament component (and not the muscles or tendons directly) the ‘vertebral column variant’ is used for modeling.

For example,

• Benign neoplasm of lumbar vertebral column (disorder) and Kyphoplasty of fracture of lumbar spine using fluoroscopic guidance (procedure) are both modeled with 122496007 |Structure of lumbar vertebral column (body structure)|.

The sacrum is considered equivalent to the sacral vertebral column, as it is composed of the bone structure of the sacrum plus the joint structure of sacrococcygeal junction of spine.

The spine is traditionally divided into the following regions:

• Cervical

• Thoracic

• Lumbar

• Sacral

The anatomy of these individual segments are structured in accordance with the description above.

The regions and joints between these identified segments are referred to as cervicothoracic, thoracolumbar, lumbosacral and sacrococcygeal. The meaning of these words are subject in common parlance and some literature to be ambiguous.

For example,

• ‘Thoracolumbar’ sometimes refers to the thoracic spine and lumbar spine, or alternatively, it is used to express the junction between the thoracic spine and lumbar spine.

To avoid false assumptions, the junction of spinal segments in SNOMED CT have been made explicit by including the word junction in descriptions. This avoids potential misinterpretation as to whether a word such as ‘thoracolumbar' relates to both spinal segments or just the adjacent volume.

For example,

• The notion of 1145014005 |Structure of thoracolumbar junction of vertebral column (body structure)| is only used for modeling when it is explicitly stated in the target concept e.g. 281907005 |Fracture dislocation of thoracolumbar junction (disorder)|.

By contrast, in the circumstance where a dependent concept relates to the combination of two segments, e.g. 702487007 |CT of thoracolumbar spine (procedure), (FSN Computed tomography of thoracic and lumbar spine), the concept is modeled with two axioms, namely Structure of lumbar vertebral column region and Structure of thoracic vertebral column region.

The volume or extent of the junctional zones themselves are not defined consistently in the literature but most commonly relate to the junction between two segments and one vertebra above and below. So the convention used in the SNOMED CT anatomy hierarchy follows this guidance.

For example,

1145014005 |Structure of thoracolumbar junction of vertebral column (body structure)| includes the following concepts in its class:

• 66794005 |Bone structure of L1 (body structure)|

• 23215003 |Bone structure of T12 (body structure)|

• 714833001 |Structure of intervertebral syndesmosis of T12 and L1 (body structure)|

In addition, a further convention is required as to where segmental junctional joints belong, i.e. either to the cephalic or caudal segment. For instance, does the T12/L1 facet joint relate to the Thoracic spine joint structure or/and Lumbar spine joint structure?

The convention used (based on common criteria of spinal injuries) is that the junctional joints are included with the cephalic segment. So, in the case of the T12/L1 facet joint, it is included in the class of Thoracic spine joint structure (body structure).

Similarly, 8454000 |Lumbar spine joint structure (body structure)| subsumes:

• Intervertebral L5-S1 disc

• Structure of lumbosacral joint

• Structure of facet joint between L5 and S1

Right, left disorder concepts

When creating a lateralized disorder concept, two concepts should be created:

1. concept for the left side

2. concept for the right side

Descriptions

• FSN: <morphologic abnormality> of _right/left_ <body structure> (disorder)

• PT: Right/left

  • For example, 1089071000119109 | Inflammation of left mastoid (disorder)|

    • FSN: Inflammation of left mastoid (disorder)

When creating a lateralized disorder concept, if a non-lateralized parent does not exist, then it should be created as well. In other words, do not just create the right and left versions, but also create a concept to represent the laterality-agnostic parent.

• For example,

  • When creating Inflammation of left mastoid and Inflammation of right mastoid, also ensure a concept for Inflammation of mastoid exists.

Where the disorder is left/right of a specific anatomical site, and the preferred term naming pattern of Right/left causes a combination that does not sound like natural flowing English, the guidance above can be circumvented. See the section and Laterality section .

• For example,

  • Left interphalangeal thumb joint open traumatic dislocation should follow naming guidance of Open traumatic dislocation of interphalangeal joint of left thumb.

  • Left abscess of foot is an incorrect term; instead, this should read Abscess of left foot.

Where the bilateral disorder description causes a combination that does not sound like natural flowing English, the guidance below can be circumvented.

• FSN: of bilateral (disorder)

• PT: Bilateral

• SYN: of bilateral

• SYN: of both

• FSN: of bilateral (disorder)

• PT: of bilateral

• SYN: of both

Note the PT of Bilateral is not required. Bilateral is to describe the body site, not the morphologic abnormality.

• For example,

  15725081000119100 | Effusion of joint of bilateral feet (disorder) |

  • FSN: Effusion of joint of bilateral feet (disorder)

  • PT: Effusion of joint of bilateral feet

Also note that joint is singular. This is to denote that the joint may be singular on each side of the body; the plurality of feet will represent the laterality. Using joints as plural may incorrectly reflect that there are multiple joints affected in both feet.

Bilateral disorders should be modeled using two relationship groups, one for each lateralized body structure.

Overview

The following modeling and terming guidelines apply to concepts in the International Release.

Modeling

"Allergy to X vaccine" concepts shall be modeled using the proximal primitive modeling pattern. Due to the small number of concepts (n<25), no template will be created. The "Allergy to substance" template can be consulted for generalized modeling guidance.

Single or multiple ingredient vaccine

The following illustrates the stated view for top level grouper 863903001 |Allergy to component of vaccine product (finding)|:

The following illustrates the inferred view for top level grouper 863903001 |Allergy to component of vaccine product (finding)|:

The following illustrates the stated view for 294663006 |Allergy to component of vaccine product containing Hepatitis A virus antigen (finding)|:

The following illustrates the inferred view for 294663006 |Allergy to component of of vaccine product containing Hepatitis A virus antigen (finding)|:

The following illustrates the stated view for 294662001 |Allergy to component of vaccine product containing Measles morbillivirus and Mumps orthorubulavirus and Rubella virus antigens (finding)|:

The following illustrates the inferred view for 294662001 |Allergy to component of vaccine product containing Measles morbillivirus and Mumps orthorubulavirus and Rubella virus antigens (finding)|:

The concept 66091009 |Congenital disease (disorder)|, means present at birth. Though the word congenital may be applied to genetic disorders, the term genetic is preferred for those disorders.

The logical definition of a congenital disorder must include:

• Occurrence = Congenital (qualifier value).

It may also include:

• Finding site = X (body structure)

• Associated morphology = X (morphologic abnormality)

• Pathological process = Pathological development process (qualifier value)

All of these defining relationships should be grouped to indicate that the abnormal morphology occurs at the finding site, results from a pathological development process, and is present at birth. Where a morphologic abnormality occurs at more than one finding site, or one body structure has multiple morphologic abnormalities, multiple relationship groups should be created and the pathological process and occurrence relationships included in each relationship group.

The following guidelines apply:

A disorder with the word congenital in the FSN should classify under 66091009 |Congenital disease (disorder)|.

Congenital X (morphologic abnormality) concepts are being inactivated hence Congenital anomaly disorder grouper concepts, such as 9904008 |Congenital anomaly of cardiovascular system (disorder)|, should be modeled with an Associated morphology (attribute) of 49755003 |Morphologically abnormal structure (morphologic abnormality)I and a Pathological process relationship.

Whether creating new or revising existing concepts, only use Congenital X (morphologic abnormality) concepts if no non-congenital supertype of that morphologic abnormality is active.

• For example, use 399898009 |Misalignment (morphologic abnormality)| not 102283003 |Congenital misalignment (morphologic abnormality)|

When modeling a congenital neoplasm disorder, the attribute-value relationship of Pathological process (attribute) = Pathological development process (qualifier value) is not used.

While some disorders are only congenital or only acquired, some disorders may be either congenital or acquired. The _ acquired_ form should only exist when there is a need to differentiate from the congenital form. Do not model a disorder as acquired if a congenital variant does not exist.

Congenital disorders are modeled using 246454002 |Occurrence (attribute)| of 255399007 |Congenital (qualifier value)|. If the FSN does not include congenital , it should not be modeled as congenital. The precise meaning of the FSN should be followed (e.g. many hereditary disorders have congenital appearances).

For example,

33534005 |Congenital bowing of femur (disorder)| is modeled with 246454002 |Occurrence (attribute)| of 255399007 |Congenital (qualifier value)|

Acquired disorders are those that originate and manifest after birth. The disorders are associated with a period of life, as opposed to a specific process or structure. All diseases (disorders) that occur after birth are considered acquired.

Generally, concepts that explicitly state acquired in the FSN or in a synonym should be modeled with Occurrence = 767023003 |Period of life beginning after birth and ending before death (qualifier value)|.

For example,

240253004 |Acquired abduction deformity of foot (disorder)| has acquired in the FSN and is modeled with Occurrence = 767023003 |Period of life beginning after birth and ending before death (qualifier value)|.

Congenital absence can represent at least three different classes of absence:

1. Total developmental absence of the affected organ/structure

2. Partial absence of the affected organ/structure

3. In utero amputation of all or part of the affected organ/structure

Conventional use of the terms aplasia and agenesis often regard these as synonymous. However, proper definitions of these terms suggests a distinction that should be made in the terminology when included in the FSN.

• Aplasia - defective development resulting in the absence of all or part of an organ or tissue.

• Agenesis - absence of an organ due to nonappearance of its primordium in the embryo. (implies complete absence)

In order to conform to the intended meaning of the FSNs as described by the original source, the following modeling patterns are proposed for congenital absence terms:

Congenital absence of X

• Associated morphology = Absence (morphologic abnormality)

• Occurrence = Congenital (qualifier value)

• Finding site = Structure of X (body structure)

Aplasia

• Associated morphology = Aplasia (morphologic abnormality)

• Occurrence = Congenital (qualifier value)

• Finding site = Structure of X (body structure)

Partial absence of X

• Associated morphology = Aplasia (morphologic abnormality) or Transverse deficiency (morphologic abnormality)

• Occurrence = Congenital (qualifier value)

• Finding site = Part of X (body structure)

Agenesis of X or Complete absence of X

• Associated morphology = Agenesis (morphologic abnormality)

• Occurrence = Congenital (qualifier value)

• Finding site = Entire X (body structure)

• Acquired abnormality of congenital anomaly

• Malformation, deformation, anomaly

Digestive tract is the same as alimentary tract, and includes the entire passage for food through the body, including mouth, oral cavity (both vestibule of mouth and cavitas oris propria), oropharynx, esophagus, stomach, duodenum, jejunum, ileum, colon, rectum, and anal canal.

Digestive system includes the digestive tract, as well as the associated organs of digestion, including tongue, teeth, salivary glands, liver, exocrine pancreas, gallbladder, and biliary tract.

Gastrointestinal tract has two meanings in common usage. One that does and one that does not include the esophagus. The usage that includes the esophagus would more correctly be named esophago-gastrointestinal tract. Endoscopists frequently use this meaning, even though it is contrary to some dictionary definitions and does not follow strict lexical interpretation (which does not include the esophagus).

Upper gastrointestinal (GI) tract. When describing upper GI bleeding and upper GI radiographic and endoscopic procedures the upper GI tract includes the esophagus, stomach, and duodenum. The upper GI tract does not include the more restricted stomach-intestine entity.

Lower gastrointestinal (GI) tract. When describing lower GI bleeding, lower GI radiographic and endoscopic procedures, and lower GI output from ileostomies and colostomies, the lower GI tract includes the jejunum, ileum, cecum, colon, rectum and anal canal. The ligament of Treitz may be used as the division between upper and lower GI tracts (and the division between the duodenum and jejunum).

Also, since the upper GI tract is said to end at the duodenum-jejunum junction, and there is no concept meaning middle GI tract, the jejunum can be inferred to be in the lower GI tract.

• See J Vasc Interv Radiol 9:747 for an example of inclusion of the jejunum and distal tract as part of the lower GI tract.

The SNOMED CT concepts 119253004 |Upper aerodigestive tract structure (body structure)| and 361922007 |Entire upper aerodigestive tract (body structure)| have the meaning based on the following reference: Cancers of the upper aerodigestive tract constitute approximately 4% of all malignancies. These include cancer of the lip, tongue, major salivary glands, gums and adjacent oral cavity tissues, floor of the mouth, tonsils, oropharynx, nasopharynx, hypopharynx and other oral regions, nasal cavity, accessory sinuses, middle ear, and larynx (Upper aerodigestive tract cancers, Cancer 1995 Jan 1;75 (1 Suppl): 147-53). This definition matches the tumors included in the CAP Cancer Checklist for upper aerodigestive tumors. The esophagus, or at least the cervical esophagus, may be included, but not in SNOMED CT.

Biliary tract includes the gallbladder, intrahepatic and extrahepatic bile ducts, and common bile duct. It does not include the liver. SNOMED CT uses biliary system as a synonym for biliary tract. SNOMED CT has another concept that does include the liver, 732049009 |Entire liver and biliary system (body structure)|.

Mouth has several different meanings including mouth region, oral region of the face, and rima oris.

Mouth region includes structures surrounding the oral cavity, as well as structures of the oral region of the face.

• Use mouth region for most disorders with a finding site of mouth.

Oral region of face includes the skin and subcutaneous tissue of the lips and perioral region, the orbicularis oris muscle, and the vessels and nerves in these structures.

Rima oris is the opening of the mouth.

The four regional parts of the tongue are the ventrum (inferior surface), dorsum, root, and body. The root of the tongue is the posterior third, the dorsal surface of which forms the anterior wall of the oropharynx. The root of the tongue rests on the floor of the mouth. The nerves and vessels that supply the intrinsic muscles of the tongue traverse the root of the tongue.

The terms colorectal and colorectum , commonly used by pathologists, are included in descriptions for concepts referring to neoplasms modeled with 1285733009 |Structure of cecum and/or colon and/or rectum (body structure)|. 1285733009 |Structure of cecum and/or colon and/or rectum (body structure)| is needed because neoplasms are the same from the cecum to rectum and are considered as a group in cancer synoptic reporting protocols. Note, there is no consensus concerning the definition of colon in the literature and between different domains.

The anatomy structures should only be pre-coordinated 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 pre-coordinated 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 post-coordinations, 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.

SNOMED CT uses the Foundation Model of Anatomy (FMA) definition of body part and body part subdivision for some concepts. For example, the joint regions discussed below are classified as body part subdivisions, since that is what is intended by the diseases and procedures that use these terms in their definitions. They are not body parts because they are defined, not by a set of bones, but rather by a particular joint and its surrounding structures. However, our interpretation of the word region is based on common usage and is intended as a three-dimensional structure, not the FMA two-dimensional definition of body region. In other words, these regions are not simply surface regions (skin), but also include the three dimensional underlying structures (subcutaneous tissues, bones, muscles, tendons, fascia, vessels and etc.).

Many concepts contain the phrase surface region. These could be interpreted as massless (immaterial) mathematical surfaces, but a clinical terminology would have no direct use for such meanings in clinical records. They could be interpreted as having mass (not immaterial), but the depth then is arbitrary. Should it be just skin deep, or should it include deeper layers of the surface? If only skin deep, the meaning of these concepts would overlap with concepts for skin regions. If deeper, the meaning would possibly be the same as the generic structure concepts.

The named regions of the abdomen are by tradition divided horizontally by the transpyloric plane and the interspinous plane, and vertically by the midclavicular plane. The lateral regions are therefore bounded above by a plane that is inferior to the ribs. In contrast, the flank is the lateral region of the abdomen bounded above by the ribs. Thus some parts of the hypochondriac regions, which are superior to the transpyloric plane but inferior to the ribs, would be considered also part of the flank. The hypogastric region is also sometimes called the pubic region.

The Structure-Entire-Part (SEP) model

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.

There are a number of concepts in the anatomy hierarchy that represent congenital cardiac malformations. This content was developed in cooperation with IPCCC (International Pediatric and Congenital Cardiac Code).

The following pairs of cardiac valve concepts do not represent the same thing and are siblings, not super- or subtypes, to each other:

• 11124005 |Atrioventricular valve (body structure)| vs. 279316009 |Atrioventricular (non-mitral, non-tricuspid) valve structure (body structure)|

• 91134007 |Mitral valve structure (body structure)| vs. 312523009 |Left (non-mitral) atrioventricular valve structure (body structure)|

The following modeling and terming guidelines apply to concepts in the International Release.

"Adverse reaction to X vaccine" concepts shall be modeled using the proximal primitive modeling pattern. Due to the small number of concepts (n<50), no template will be created. The "Adverse reaction to substance" template can be consulted for generalized modeling guidance.

Single or multiple ingredient vaccine

The skeletal system (systema skeletal in Nomina Anatomica) includes bones and cartilage. The bony skeleton includes bones only. The vertebral column is part of the skeletal system and includes the intervertebral discs (fibrocartilage). Individual vertebrae are part of the bony skeleton.

In ordinary usage, bone combines the meanings bone organ and bone tissue.

The 5 anatomical concepts related to bone are:

1. 3138006 |Bone (tissue) structure (body structure)|. Tissue type that makes up bones; a quantity of regular connective tissue consisting of osteocytes and related cells, the intercellular matrix of which is ossified; or any part thereof.

When authoring in this domain, these are the approved attributes and allowable ranges.

See also the respective .