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© 2024 International Health Terminology Standards Development Organisation.  All rights reserved.  SNOMED CT® was originally created by the College of American Pathologists.

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Page At A Glance

Table Of Contents

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 January 2018 release of SNOMED Clinical Terms® (SCT) International Release.

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

This document is available alongside the January 2018 International Edition release.

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 during the release.

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 January 2018 International Edition release.


2 Content Development Activity

2.1 Summary

Continuous quality improvement and enhancement of existing content is ongoing based on requests received via the Content Request System (CRS). A review of the pre-coordination patterns that are blocking CRS tickets from progressing has commenced and will continue into 2018.

A review of requests currently in the 'In Inception' status in the CRS tool is underway and where it is feasible to progress a request prior to resolving the tracker issue, the request is being identified for progression. Given this work (and the pre-coordination patterns review) the number of requests in 'In Inception' status has decreased by over 1000. This work will continue into 2018.

The January 2018 International Release has seen a continuation of the work driven by contributions from: Kaiser Permanente Convergent Medical Terminology (CMT), Global Medical Device Nomenclature Agency (GMDNA), World Health Organization (WHO) ICD-11 Beta and International Classification for Nursing Practice ( ICNP®) to add new content to SNOMED CT.  

Additionally, member-identified priority projects, have driven enhancements in the anatomy hierarchy, while other project-driven changes have resulted in new content additions and enhancements to existing content detailed below.

Advance Warning

Inactivation reason of LIMITED/WAS A will no longer be allowed for any content after the January 2018 release. The WAS A association refset will not be updated thereafter.


In 2015, a proposal was made to inactivate 159083000 |WAS A (attribute)| relationship and stop updating the 900000000000528000|WAS A association reference set (foundation metadata concept)| at the Editorial Advisory Group.

Since these recommendations were made, a formal proposal for the technical approach to batch updating the terminology was created and a notice of the proposed inactivation sent to the Community of Practice.

The implementation of changes was postponed following feedback on utility for implementation and the potential impact to customers who were still using RF1.

The matter was discussed again at the meeting of the Editorial Advisory Group in Bratislava in October 2017. Since the requirements and potential issues can be addressed by deriving such information from the RF2 release format, the recommendation is to proceed the decision after the January 2018 release.

2.2 Content Quality Improvement

4979 new concepts were added

SCT StatisticsNew concept additions
Body structure (body structure)571
Clinical finding (finding)2005
Event (event)12
Observable entity (observable entity)52
Organism (organism)256
Pharmaceutical / biologic product (product)10
Physical object (physical object)171
Procedure (procedure)911
Qualifier value (qualifier value)420
Record artifact (record artifact)115
SNOMED CT Model Component (metadata)29
Situation with explicit context (situation)91
Social context (social concept)10
Specimen (specimen)35
Staging and scales (staging scale)13
Substance (substance)278

21080 changes were made to existing content

SCT Improvement Statistics to Existing ConceptsNumber
Total number of changes21080
Change to stated concept definition7597
Change to inferred concept definition15635
Change in concept definition status from Primitive to Sufficiently Defined 796
Description change6051
Inactivated concepts781
Inactivated descriptions4102
Reactivated concepts14

2.2.1 Anatomy 

New anatomy concepts: 571

        • 462 new lateralized body structure concepts and nearly 1000 new lateralized findings, disorders and procedures. There are over 5,000 lateralized concepts in SNOMED CT.
        • 30 new concepts for 736503009 | Structure of mucous membrane of nasal cavity and/or nasal sinus (body structure)| and descendants and refined the existing hierarchical relationships.
        • New concepts for transplanted cardiac values and structure of vertebral column and/or spinal cord to support concept modeling from ICD-11 content.

Reviewed and updated IS A relationships for 1,255 skin structure concepts according to the new anatomy model:

        • Identified and added 329 new IS A relationships. 
        • Inactivated 136 redundant or incorrect IS A relationships.

Updates for SEP refsets and Lateralizable body structure refset:

        • 42 changes to the SE refset.
        • 4 changes to the SP refset.
        • 42 new members for lateralizable body structure refset and 10 inactivations.

2.2.2 Clinical finding

New concepts for clinical findings and disorders: 2005

Work completed on the following Content Projects:

        • IHTSDO-418 - 84017003 | Bursitis (disorder).
        • IHTSDO-772 - Suspected - findings / disorders, should be situations.
        • IHTSDO-412 - Intra-operative complication.

Work commenced on the following Content Projects:

        • IHTSDO-451 - Has definitional manifestation.
        • IHTSDO-703 - Inactivation of 'unilateral' concepts.
        • IHTSDO-614 - Rework hierarchy 441457006|Cyst (disorder)|.

Other content quality improvements:

        • Remodel and fully define 63491006|Intermittent claudication (finding) and subtypes.
        • Review and remodel of 128200000|Complex regional pain syndrome (disorder)| and subtypes.
        • 7 new laboratory finding concepts added along with 30 changes made to existing laboratory concepts.
        • Revision of spinal injury content - many concepts were primitives and represented as flat list under 26738009|Spinal cord injury without spinal bone injury (disorder)|. This sub-hierarchy has been reviewed and 85 concepts have been remodeled. Most concepts have been defined based on complete, incomplete injuries and levels. These changes have also addressed the reported duplication issues.
        • Remodel 3238004|Pericarditis (disorder)| and subtypes with primitive parent and changes to relationship groups where required to achieve consistency, approximately 100 concepts were remodeled.

2.2.3 Convergent Medical Terminologies (CMT)

New CMT concepts: 766

These were added across 3 domains:

        • CMT Neurology
        • CMT Musculoskeletal
        • CMT Radiology

2.2.4 Procedure Hierarchy

New concepts for procedure hierarchy: 911

Diagnostic Imaging - approximately 363 new concepts added including:

      • MRI 53
      • CT 38
      • Plain X-ray 15
      • Fluoroscopy 73
      • Imaging guided procedure (various modalities) 102
      • Ultrasonography 82

Work completed on the following Content Projects: 

        • IHTSDO-111 - Review of hierarchy 23968004|Colectomy (procedure) with inactivation of duplicate content, concepts remodeled with primitive parent and changes to relationship groups where required.
        • IHTSDO-691 - Remodel content 243185007 | Advanced life support (procedure) and subtypes.

Other content quality improvements:

        • Remodel and fully define 180081001|Correction of congenital deformity of hand (procedure)| and its descendants.
        • Fixed MRCM rule violation for 156 Evaluation procedures and removed Observable entities as values for Component Attribute.

        • Care program approach - realm specific concepts inactivated from International release.

2.2.5 Collaboration/Harmonization Projects Orphanet

As a result of collaboration with Orphanet ( 12 new SNOMED CT concepts have been created to represent rare diseases in the disorder hierarchy. ICD-11 Harmonization plan

Added 1100 concepts equivalent to ICD-11 Mortality and Morbidity Statistics (ICD-11-MMS) codes; review and additions are ongoing based on updates to ICD-11-MMS. LOINC

105 new SNOMED CT concepts created for LOINC - SNOMED collaboration project. International Classification for Nursing Practice ( ICNP®)

74 new SNOMED CT concepts created as a requirement for the ICNP-SNOMED CT Equivalence Table. Global Medical Device Nomenclature Agency (GMDNA)

165 new SNOMED CT concepts created in the Physical object hierarchy to support the GMDN collaboration agreement.

2.2.6 Morphologic Abnormality

New concepts added: 22

There are 8 updates for the ICD-O maps in 2018 January release.

2.2.7 Observable Entity

New concepts added: 52

Content quality improvements:

        • Inactivated 704318007 |Property type (attribute)| and replaced it with 370130000 |Property (attribute) for 162 modeled Observable entity concepts which had previously used 704318007 |Property type (attribute)|. Updated related MRCM rules and Editorial Guide.

2.2.8 Organism

New organism concepts added: 236

Changes to 29 existing concepts in the organism hierarchy.

2.2.9 Pharmaceutical / biologic product

Drug model project

For further details on the planned changes in this area, please refer to the Drug Model Working Group Directory section.

Please note, you may have to register for Confluence user account in order to access this project.

Summary of changes

New hierarchies
  • Basic dose form (basic dose form)
    • New concepts created (n ≈ 125)
  • Dose form administration method (administration method)
    • New concepts created (n ≈ 10)
  • Dose form intended site (intended site)
    • New concepts created (n ≈ 20)
  • Dose form release characteristic (release characteristic)
    • New concepts created (n ≈ 5)
  • Dose form transformation (transformation)
    • New concepts created (n ≈ 5)
  • Pharmaceutical dose form (dose form)
    • New concepts created or remodeled (n ≈ 250)
  • State of matter (state of matter)
    • New concepts created (n ≈ 5)
New semantic tags
  • (administration method)
  • (basic dose form)
  • (dose form)
  • (intended site)
  • (release characteristic)
  • (state of matter)
  • (transformation)

New attribute types

  • Has basic dose form
  • Has concentration strength denominator unit
  • Has concentration strength denominator value
  • Has concentration strength numerator unit
  • Has concentration strength numerator value
  • Has dose form administration method
  • Has dose form intended site
  • Has dose form release characteristic
  • Has dose form transformation
  • Has state of matter
  • Has ingredient
  • Has precise active ingredient
Medicinal Product (MP)

Updated ≈ 1100 existing concepts in accordance with new modeling and/or terming guidelines

  • Existing concept IDs, stated parents and definition status were retained
  • Missing |Has active ingredient| attributes were added; errors in existing content were corrected as they were identified
Medicinal Product Form (MPF)
  • Negligible number of changes.
Clinical Drug (CD)

Updated ≈ 3000 existing concepts changing terming from "Product containing X" to "Product containing only X"

  • Note that the terming for these concepts was updated in the 2017-July release to reflect "Product containing X"; upon advice from the Working Group, we elected to notifiy the Member Forum, Project Group, and Working Group of the retraction/substitution rather than inactivate/replace these concepts.
New or updated concepts to support future simple map refset development

For SNOMED CT to EDQM simple map refset:

  • 741068007|SNOMED CT to European Directorate for the Quality of Medicines & HealthCare simple map reference set module (core metadata concept)
  • 735233007|European Directorate for the Quality of Medicines & HealthCare simple map reference set (foundation metadata concept)

For SNOMED CT to UCUM simple map refset:

  • 741814003|SNOMED CT to Unified Code for Units of Measure simple map reference set module (core metadata concept)
  • 733900009|Unified Code for Units of Measure simple map reference set (foundation metadata concept)
Content maintenance including
  • Content:
    • Inactivation of concepts that are missing strength denominator
    • Inactivation of concepts that refer to color
    • Inactivation of concepts containing caplet
    • Inactivation of concepts containing "controlled-release"
  • Documentation created or updated:
    • Position Statement
    • Briefing Paper re: update terming for Clinical Drug concepts changing "Product containing X" to "Product containing only X"
    • Editorial Guidelines for Modeling and Terming for Dose Form related hierarchies, including including identification of |Pharmaceutical dose form| concepts to be used for modeling concepts in the International Release moving forward
    • Editorial Gudielines for Modeling and Terming for Product hierarchy

2.2.10 Veterinary Extension

2 concepts were moved to the Veterinary Extension. 

2.2.11 Situation with Explicit Context

Number of concepts added to Situation hierarchy: 91

Work completed on the following Content Projects:

        • artf222723 - 19 new concepts for situation hierarchy to replace inactivated concepts in the event hierarchy 398033008|Death of relative (event)|.

Work commenced on the following Content Projects:

        • IHTSDO-703 - The inactivation of 'unilateral' concepts with creation of lateralised replacement concepts where not already present in the terminology has commenced. This work will continue into 2018.

2.2.12 Record Artifact

New concepts added: 82. This number includes 5 new concepts for 'care plan' which replace inactivated concepts in the qualifier value hierarchy.

2.2.13 Specimen

New concepts added: 30

2.2.14 Substances

The following changes will be included in the 2018-January International Release.

New hierarchies
    • Disposition (disposition)
      • New concepts created (n ≈ 250)
New semantic tags
    • (disposition)

New attribute types

    • Has disposition
    • Is modification of

Documentation created or updated including:

      • Editorial Guidelines for Modeling and Terming for Substance hierarchy.
      • Editorial Guidelines for Modeling and Terming for Disposition hierarchy.

Content updates include:

      • Populated new Disposition hierarchy with approximately 250 new concepts as descendants of 726711005|Disposition (disposition).
      • Updated terming and modeling for approximately 200 existing concepts that represent disposition groupers, making the concepts fully defined and removing stated descendants. As a result, approximately 9000 stated descendants were remodeled with new stated parents.
      • Added new Has disposition attribute for approximately 4200 concepts.
      • Completed review of concepts as a result of gap analysis to identify missing concepts representing hydrates, with 14 new concepts added. (Note: there were 87 new concepts added for 2017-July Release.) Three concepts were rejected (e.g. out of scope, duplicate of existing concept).

Release plans, Substance hierarchy

For further details on the planned changes in this area, please refer to the Substances project.

Please note, you may have to register for Confluence user account in order to access this project.

2.3. Internal Quality Improvement

2.3.1 Case Significance Indicator

In order to align in accordance with the RF2 specification, a technical batch change was made to the case significance value for approximately 1400 descriptions.

2.3.2 Logic Profile Enhancements

Content changes have been made to support the logic profile enhancements.

New OWL expression reference set type will have OWL ontology refset and OWL axiom refset.

New attributes |Concept model object attribute| and |Concept model data property| have been added to make clear distinction between object attribute and data attribute.

All existing attributes under concept model attribute are moved under |Concept model object attribute|. The data properties in national extensions should be moved under the new attribute |Concept model data property|

2.3.3 Dentistry Odontogram Refset

63 new concepts added to support Dentistry.

The first production release of the Odontogram Refset was made available in October 2017.

2.3.4 Machine Readable Concept Model (MRCM)

17 new changes or updates in the MRCM refsets and authoring platform. 

The majority of changes were required to support development of the concept model for drugs and observable entity. 

2.4 SNOMED CT derived products

2.4.1 ICD-10 map

The SNOMED CT to the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (© World Health organisation 1994) 2016 Version map (SNOMED CT to ICD-10 Map) is included in the SNOMED CT International release 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 Centres.

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_20170131.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 |ICD-10 complex map reference set (foundation metadata concept)|. 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 January 2018

The map provided for the January 2018 release has been updated, and now represents a complete map from SNOMED CT International release to ICD-10 2016 version.

    • 2207 new concepts added

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


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 capacity within the current editing cycle, 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 Snomed CT January 2018 International edition, the following Known Issues were identified, and agreed to be resolved in the next editing cycle (to be published in July 2018):

Key Summary Description

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 - in this case the January 2018 International Edition.  They can also be issues found during the Alpha and Beta testing of the current release, which were resolved before the final deployment of the associated Member 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 Snomed CT January 2018 International edition can be found here:

Key Summary Description Resolved

3.3 Technical updates

3.3.1  Association Reference set naming convention

The naming convention of the Association Reference file is being improved for the January 2018 International Edition.

It will no longer be named using this convention:


Instead it will be named as follows:


Therefore, the three files in the January 2018 International Edition release package will be called:

  • der2_cRefset_AssociationDelta_INT_20180131.txt
  • der2_cRefset_AssociationFull_INT_20180131.txt
  • der2_cRefset_AssociationSnapshot_INT_20180131.txt

3.3.2  RF2 package naming convention

In order to differentiate between the different versions of the Production release package, the fourth element in the naming convention of will now state "MEMBER" for Member releases, and "PRODUCTION" for the final Public releases.

Thus the Member release published on 31st December 2017 for the January 2018 International Edition will be called:

Whilst the Public release published on 31st January 2018 for the January 2018 International Edition will be called: 

3.3.3  RF2 package format

For future reference, the RF2 package convention dictates that it contains all relevant files, regardless of whether or not there is content to be included in each particular release.  Therefore, the package contains a mixture of files which contain both header rows and content data, and also files that are intentionally left blank (including only a header record).  The reason that these files are not removed from 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 this or future releases, and 
  2. ...files that just happen to contain no data in this particular release (and are therefore included in the package but left blank, with only a header record), but are still relevant to RF2, and could therefore potentially contain data in future releases.

This allows users to easily distinguish between files that have purposefully been removed or not, as otherwise if files in option 2 above were left out of the package it could be interpreted as an error, rather than an intentional lack of content in that release.

3.3.4  Early visibility of impending change in the July 2018 International edition

Please see the following page for details of all upcoming changes planned for July 2018 and beyond:  January 2020 Early Visibility Release Notices - Planned changes to upcoming SNOMED International Release packages

NOTE:  To access any of the links in the pdf document, please visit the Release Notes online here:



Final Version




Lesley MacNeilLMA Approved
 Maria BraithwaiteMBR approved - Section 3.0 Technical notes to be completed by AAT

Donna MorganDMO Approved
Jim Case/Paul Amos LMA Approved - via email in absence to document access


Rory DavidsonSigned off


Maria BraithwaiteSigned off


Lesley MacNeilSigned off





Draft Amendment History








Andrew Atkinson

First draft for review and comment


20171115Lesley MacNeilAdded Paul Amos for Approval in absence of Jim Case - Also notes to MBR to add advance notice of WAS A usage new policy
1.020171120Andrew AtkinsonFinal technical updates completed
1.120180129Andrew AtkinsonUpdated with latest Member release package updates




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