1. Introduction

1.1. Background

SNOMED CT terminology provides a common language that enables a consistent way of indexing, storing, retrieving, and aggregating clinical data across specialties and sites of care.

SNOMED International maintains the SNOMED CT technical design, the content architecture, the SNOMED CT content (includes the concepts table, the descriptions table, the relationships table, a history table, and ICD mappings), and related technical documentation.

1.2. Purpose

This document provides a summarized description of the content changes included in the February 2024 release of SNOMED Clinical Terms^® (SCT) International Edition.

It also includes notes detailing the known content or technical issues where the root cause is understood, the fix has been discussed and agreed to, but has yet to be implemented.

The SNOMED International release notes are available alongside the February 2024 International Edition.

1.3. Scope

This document is written for the purpose described above and is not intended to provide details of the technical specifications for SNOMED CT or encompass every change made.

1.4. Audience

The audience includes National Release Centers, WHO-FIC release centers, vendors of electronic health records, terminology developers and managers who wish to have an understanding of changes that have been incorporated into the February 2024 International Edition.

Please note, you may have to register for a Confluence user account in order to access the links included in these release notes.

1.5. Important Information

2. Content Development Activity

2.1. Summary

Continuous quality improvement and enhancement of existing content is an ongoing process undertaken by SNOMED International in preparation for every release. The February 2024 International Edition has seen a continuation of the work driven by contributions from: Kaiser Permanente i.e. Convergent Medical Terminology (CMT), Global Medical Device Nomenclature Agency (GMDNA), Orphanet and other domain specific collaborations as well as requests received via the Content Request System (CRS). 

Additionally quality improvement activities are advanced via project driven initiatives summarized below.  Additional work items impacting every release are updates to the SNOMED CT derived maps such as ICD-10 and ICD-O; details are included in these release notes.  

Information about editorial decisions may be found in the SNOMED CT Editorial Guide; mapping guidance for ICD-10 can be found here.

2.2. Quality Initiative

The Quality Initiative (QI) project is the implementation of the Quality Strategy. After a successful pilot project for the July 2018 Edition the next stage has been implemented for subsequent releases including February 2024. 

Quality improvement tasks are being deployed to improve internal structural consistency and ensure compliance with editorial policy related to the stated modeling of content. Additionally, correction or addition of defining relationships is being carried out to accurately reflect current clinical knowledge and ensure the semantic reliability of descriptions associated with a concept. 

2.2.1.  Replacement for En Dash 

40 published descriptions with an unexpected en dash have been replaced with a description with a hyphen and the Editorial Guide has been updated.

2.2.2. Update Umbilical Cord Clinical Finding and Disorder Concepts

The embryological origin of the umbilical cord is derived from the fetus and is thus a fetal structure. All disorders of the umbilical cord have been remodeled as disorders occurring in the fetal and /or neonatal period.

Number of concepts edited (approx): 125

2.2.3. Update Exteriorization Procedure Concepts

Concepts currently modelled with 129354008 |Exteriorization - action (qualifier value)| are under review and are being remodeled where appropriate.

Number of concepts edited (approx): 90

2.2.4. Update Grafting Procedure Concepts

Subtypes of 91157001 |Grafting of fascia (procedure)|, 71081000 |Grafting of muscle (procedure)|, 392323002 |Grafting of cartilage (procedure)| have been remodeled:

• 16 subtypes of 91157001 |Grafting of fascia (procedure)| (description updated to 91157001 |Grafting of fascial graft (procedure)|) have been remodeled:
  • For procedures involving grafting of fascial grafting material a new relationship of 363701004 |Direct substance (attribute)| = 289973005 |Fascia tissue material (substance)| has been added.
  • For concepts that are not specified as to recipient site of the fascial graft, then the procedure site has been removed. 2 concepts have been inactivated as ambiguous and replaced.
• 68 subtypes of 71081000 |Grafting of muscle (procedure)| (description updated to 71081000 |Grafting of muscle graft (procedure)|) have been remodeled:
  • 16 procedures relating to muscle graft have been remodeled.
  • For procedures involving grafting of muscle tissue material a new relationship of 363701004 |Direct substance (attribute)| = 1290282008 |Muscle graft - material (substance)| has been added.
  • 247909004 |Exenteration of orbit without skin graft, with temporalis muscle transplant (procedure)| has been inactivated with reason duplicate.
• 392323002 |Grafting of cartilage (procedure)| (description updated to 392323002 |Grafting of cartilage graft (procedure)|) has been remodeled:
  • For procedures involving grafting of cartilage a relationship of 363701004 |Direct substance (attribute)| = 1290296002 |Cartilage graft - material (substance)| has been added. The concept previously had 13 descendants and now has 21 inferred descendants after remodeling and classification.

2.2.5. Update 77465005 |Transplantation (procedure) and Descendants

Work has commenced to update 77465005|Transplantation (procedure)| and descendants:

• 77465005 |Transplantation (procedure) has been remodeled with 410820007 |Surgical transplantation - action (qualifier value).
• 410820007 |Surgical transplantation - action (qualifier value)| and 129407005 |Grafting - action (qualifier value)| are now siblings (not child-parent relationship) and subtypes of 129338005 |Surgical implantation - action (qualifier value)|.
• 129347002 |Surgical transfer - action (qualifier value)| is no longer a subtype of 410820007 |Surgical transplantation - action (qualifier value)|.
• 115956009 |Release (procedure)| has been inactivated and its subtypes remodeled.
• ‌The descriptions for << 422285003 |Solid organ graft - material (substance)| and its subtypes have been updated from 'graft' to 'transplant'. For example, 420291005 |Transplant heart (substance)|.
• Grafting procedures that were subtypes of transplantation procedure have been remodeled with 129407005 |Grafting - action (qualifier value)|.

Note: this QI project is still ongoing.

2.2.6. Update Endoscopy Procedure Concepts

Concept inactivations:

• 444137001 |Endoscopy of esophagus with endoscopic ultrasound of upper gastrointestinal tract (procedure)|
• 443021000 |Esophagogastroduodenoscopy with endoscopic ultrasound of upper gastrointestinal tract (procedure)|

New concept added 1297086000 |Echoendoscope (physical object)| to define 450556004 |Endoscopic ultrasonography (procedure)| and subtypes.

Number of concepts edited (approx): 60

2.2.7. Update 73632009 |Laparoscopy (procedure)| and Subtypes 

A bulk update has been implemented to align 73632009 |Laparoscopy (procedure)| and subtypes with the template.

These changes include the addition of INCISION ROLE GROUP and INSPECTION ROLE GROUP for all Laparoscopic procedures. 

2.2.8. Update Neurology Procedure Concepts

Procedure site 280369009|Brain tissue structure (body structure)| used in the modeling of neurological procedures has been replaced with 'brain structure' to improve consistency of modeling within the domain.

Number of concepts edited (approx): 60

2.2.9. Update for Diabetes Insipidus

Following a report from October 2022 by the Working Group for Renaming Diabetes Insipidus, concepts using the term “Diabetes insipidus” have been renamed or replaced with descriptions that more appropriately represent the pathophysiology of this condition. 

The top-level concept replacing 15771004|Diabetes insipidus (disorder)| is 1296758008 |Arginine vasopressin-related polyuria (disorder)| and the specific subtypes are represented by two renamed conditions: 

• 45369008 |Arginine vasopressin deficiency (disorder)| for central etiologies

• 111395007 |Arginine vasopressin resistance (disorder)| for nephrogenic etiologies

The legacy descriptions of "Diabetes insipidus", "Central diabetes insipidus" and "Nephrogenic diabetes insipidus" have been retained where appropriate to facilitate retrieval of concepts by their newer names. 

Number of concepts edited (approx): 18

2.2.10. Review 17423001 |Epiphysiodesis (procedure) and Remodel Subtypes Epiphyseal Stapling

Epiphyseal stapling concepts have been remodeled and are no longer a subtype of 17423001 |Epiphysiodesis (procedure)|. 

Epiphysiodesis is a fusion of the epiphyseal plate resulting in a permanent arrest of growth, whereas Epiphyseal stapling is a fixation of the epiphyseal plate in order to arrest growth and is often reversible once the staples are removed.  

2.2.11. Update Superficial Injury Disorder Concepts

Further improvements have been made to the area of superficial injury disorders to improve consistency of modeling within the domain.

2.3.  Body Structure 

2.3.1.  New Concepts Autonomic Nervous System

New concepts have been added for the autonomic nervous system:

• 1296727007 |Structure of autonomic nervous system of trunk (body structure)|
• 1296725004 |Structure of autonomic nervous system of pelvis (body structure)|
• 1296697009 |Structure of autonomic nervous system of thorax (body structure)|
• 1296722001 |Structure of autonomic nervous system of abdomen (body structure)|
• 1296687000 |Structure of autonomic nervous system of lower limb (body structure)|
• 1296693008 |Structure of autonomic nervous system of upper limb (body structure)|
• 1296729005 |Structure of autonomic nervous system of head and/or neck (body structure)|

The subhierarchy of 72167002|Autonomic nervous system structure (body structure)| has been reviewed, more than 100 hierarchical relationships have been improved by adding missing relationships or correcting inconsistencies in published relationships.

2.3.2. New Concepts for Brain Tract

New concepts relating to tracts of the brain have been added - specifically tracts that reside entirely within the brain (thus excluding those tracts that extend into the spinal cord).

Number of concepts edited (approx): 50

2.3.3. Inactivation of Congenital Morphologic Abnormality Concepts

The following concepts have been inactivated and replaced with a new concept that does not specify 'congenital' in the descriptions:

• 37764001 |Congenital abnormal fusion (morphologic abnormality)|
• 67798003 |Congenital premature fusion (morphologic abnormality)|

These concepts have been replaced by:

• 1297033003 |Abnormal fusion (morphologic abnormality)|
• 1297034009 |Premature fusion (morphologic abnormality)|

Clinical finding and Procedure concepts which were modeled using the inactive concepts have been remodeled using the two new concepts. Occurrence may be recorded separately, these changes align with the Editorial Guide.

2.3.4. SEP and Laterality Anatomy Reference Sets

The release file for the lateralizable body structure reference set has been updated and validated.

The release file for the SEP reference set has been updated and validated.

2.4. Clinical Finding

2.4.1. Inactivation of 106109006|Number of previous induced termination of pregnancy (finding)| and subtypes

106109006|Number of previous induced termination of pregnancy (finding)| and subtypes have been inactivated and replaced by a new concept in the situation with explicit context hierarchy:

• 1300163008 |Past pregnancy history of multiple induced termination of pregnancy (situation)|

This concept is already published:

• 713649008 |Past pregnancy history of induced termination of pregnancy (situation)|

2.4.2. Revision of 127575007 |Malignant neuroendocrine neoplasm, epithelial (morphologic abnormality)| and Subtypes 

127575007 |Malignant neuroendocrine neoplasm, epithelial (morphologic abnormality)|, its subtypes and related disorder concepts have been revised to align with the 5th edition of the WHO Blue Book chapter on Endocrine and Neuroendocrine Tumours as part of the Histology Quality Improvement Project.

Please see the relevant briefing note for more information on the changes.

2.5. Collaboration/Harmonization Agreements

2.5.1. Social Care

Six new concepts in the clinical finding hierarchy and have been added to support social care for older people.

2.5.2. Convergent Medical Terminology (CMT)

531 CMT concepts have been added. These are predominately in the areas of musculoskeletal and ophthalmology.

2.5.3. Orphanet

Working in collaboration with Orphanet (http://www.orpha.net/consor/cgi-bin/index.php), efforts are ongoing to update rare disease concepts in SNOMED CT to maintain alignment with Orphanet for the annual update of the SNOMED CT to Orphanet Maps.

All of the concepts added for the Orphanet project have been mapped to ICD-10.

2.5.4. Cancer Synoptic Reporting

Cancer synoptic reports are used by many member countries to record pathology examination of cancer specimens including the College of American Pathologists (US and Canada), Royal College of Pathology (UK), Royal College of Pathology Australasia (Australia, New Zealand), PALGA (The Netherlands), Swedish Society of Pathology, and others.

For more information about this project, please see Cancer Synoptic Reporting Clinical Project Group 

2.5.5. International League Against Epilepsy (ILAE)

In line with approved harmonized terminology, this project is working on alignment including restructuring to update the hierarchy  << 313307000 |Epileptic seizure (finding)|.

For February 2024, work has been undertaken in the area of status epilepticus. Changes included concept inactivation and creation, change of semantic tag from (disorder) to (finding) and the addition of definitions. The finding site values for neonatal seizure concepts have been updated to Brain structure (body structure).

Further information about the changes is available here. 

2.5.6. Gravity Project

23 new Gravity concepts have been added:

• 19 Procedure concepts with a focus on education, evaluation and referral to different programs e.g. vocational education.
• 4 Clinical Finding concepts focusing on completion of education or skills training.

2.6. Internal Quality Improvement

2.6.1. Machine Readable Concept Model (MRCM) Changes

No  changes have been made for the February 2024 release.

Future changes that are currently in progress can be viewed via the MRCM Daily Build Browser

Please see early visibility for future planned changes to MRCM.

2.6.2. OWL Axiom Expressions for Annotation Properties

The new annotation properties should be represented in the OWL expression axiom refset as follows:

• The 1295447006 |Annotation attribute (attribute)| is correctly represented as subClassOf

  • 01300ccd-d1d7-417d-a70a-f688e72c4d8c 20231201 1 900000000000012004 733073007 1295447006 SubClassOf(:1295447006 :246061005)

• However, all subconcepts of 1295447006 |Annotation attribute (attribute)| should be represented as "SubAnnotationPropertyOf", instead of "subClassOf" as they currently are.

  • e6cd65fe-cb81-4db4-9ac4-040dc74fce28 20231201 1 900000000000012004 733073007 1295448001 SubClassOf(:1295448001 :1295447006)

  • 3729ce47-a96e-4dc7-9eff-83c34740c414 20231201 1 900000000000012004 733073007 1295449009 SubClassOf(:1295449009 :1295447006)

They should therefore be changed to:

• SubAnnotationPropertyOf(:1295448001 :1295447006)

• SubAnnotationPropertyOf(:1295449009 :1295447006)

However, the authoring tool will then need to be updated to ensure all new subconcepts of 1295447006 |Annotation attribute (attribute)| will be represented as SubAnnotationPropertyOf() in the future.  Numerous other tools will also need to be updated first in order to correctly consume the new format.

There are numerous systems that require updating, and that this will therefore need to be carefully tested and rolled out over the next few months.  As the potential impact was analysed and deemed to be low, the Annotations deployment will still go ahead as planned from the January 2024 International Edition release, whereas these axiom updates will be published in subsequent releases.  Please, therefore, be aware that this issue will persist for the first few International Edition releases of 2024.

2.7. SNOMED CT derived products

2.7.1. ICD-10 map

The SNOMED CT to the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (© World Health Organization 1994) 2016 Version map (SNOMED CT to ICD-10 Map) is included in the SNOMED CT International Edition as a Baseline. The SNOMED CT to ICD-10 Map was created to support the epidemiological, statistical and administrative reporting needs of SNOMED International member countries and WHO Collaborating Centers.

The SNOMED CT to ICD-10 Map is released in Release Format 2 (RF2) only. It is located in the file der2_iisssccRefset_ExtendedMapFull_INT_20200731.txt, which is in the Map folder under Refset, in each of the three RF2 Release Type folders. 

The SNOMED CT to ICD-10 Map is released as Refset 447562003 |SNOMED CT to ICD-10 extended map (foundation metadata concept).

The ICD-10 Mapping Technical Guide (including exemplars) is hosted here https://confluence.ihtsdotools.org/display/DOCICD10

2.7.2. Content Development Activity Summary

The map is a directed set of relationships from SNOMED CT source concepts to ICD-10 target classification codes.  The SNOMED CT source domains for the MAP are limited to subtypes of 404684003 |clinical finding|, 272379006 |event| and 243796009 |situation with explicit context|.  The target classification codes are ICD-10 2016 release. 

Mapped content for February 2024

The map provided for the February 2024 International Edition has been updated, and now represents a complete map from SNOMED CT International Edition to ICD-10 2016 version.

• 990 newly authored concepts have been added and mapped.

• The SNOMED to ICD-O (morphology) map has 7 additional concepts added as a result of the ICD-O 3.2 review or added due to CRS requests. 

We would welcome feedback on any issues that users of the map may detect when using the map. Issues should be submitted via mapping@snomed.org

2.7.3. SNOMED CT to OWL conversion and classification

The repository containing the toolkit enabling simple SNOMED CT to OWL conversion and classification can be found here, including documentation on its use: https://github.com/IHTSDO/snomed-owl-toolkit

Please contact SNOMED International at support@snomed.org if you would like to provide any feedback on ways to extend and improve the new toolkit.

3. Technical notes

3.1. Known Issues

Known Issues are content or technical issues where the root cause is understood, and the resolution has been discussed and agreed but has yet to be implemented.  This can be due to a number of reasons, from lack of time within the new monthly editing cycles, to the risk of impact to the stability of SNOMED CT if the fix were to be deployed at that stage in the Product lifecycle.  

For the current SNOMED CT International edition, the following Known Issues were identified, and agreed to be resolved in future editing cycles:

3.2. Resolved Issues

Resolved issues are Known Issues which were not fixed as part of the previous release lifecycle, but which have now been resolved in the latest release.  They can also be issues found during testing of the current release, which were resolved before the final deployment of the Production release.  Finally they can be issues which were reported or found during the testing phase, but which have been closed without any action taken.  

The Resolved Issues for the current SNOMED CT International edition can be found here:

3.3. Technical updates

3.3.1. RF2 package format

The RF2 package convention dictates that all relevant files are included, regardless of whether or not there is content to be included in each release.  Therefore, the package contains a mixture of files which contain both header rows and content data, and files that (intentionally) include only header records.  The reason that these "empty" files are included in the package is to draw a clear distinction between:

1. ...files that have been deprecated (and therefore removed from the package completely), due to the content no longer being relevant to RF2 in future releases 

2. ...files that happen to contain no data in this particular release (and are therefore included in the package with just a header record), but are still relevant to RF2, and could therefore contain content in future releases.

This allows users to easily distinguish between the two scenarios, as otherwise if files in option 2 were left out of the package it could be interpreted as an error, rather than an intentional lack of content in that release.

3.3.2. Changes to the International Edition package format

In line with the new implementation of Annotations, two new refsets have been added to the International Edition Release package, from December 2023 onwards:

• der2_scsRefset_ComponentAnnotationStringValueSnapshot_INT_20240101.txt
• der2_sscsRefset_MemberAnnotationStringValueSnapshot_INT_20240101.txt

These refset files are empty for the February 2024 release, whilst content is authored in future editing cycles.  However, they will then be populated with Annotations data from one of the future 2024 International Edition releases onwards (date to be confirmed).  These improvements were introduced in the December 2023 International Edition release, and will be used in all future International Edition releases until further notice.

If you have any feedback on the format of these new files please provide it URGENTLY, as changes can potentially be made now (subject to relevant approvals), before the files are populated. 

3.3.3. Proposed change to the Annotations Refset format

3.3.4. Early visibility of impending changes in the upcoming 2024 Monthly International Edition releases

Please see the early visibility Confluence page for details of forthcoming changes.