Introduction

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.

Purpose

This document provides a summarized description of the content changes included in the May 2025 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 May 2025 International Edition.

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.

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 May 2025 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.

Content Development Activity

Summary

Continuous quality improvement and enhancement of existing content is an ongoing process undertaken by SNOMED International in preparation for every release. The May 2025 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). 

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

Quality Initiative

The Quality Initiative (QI) project is the implementation of the Quality Strategy. After a successful pilot project for the July 2018 Edition release, the next stage has been implemented for subsequent releases including May 2025. 

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.

Body Structure 

Revision of 707861009|Structure of skin and/or skin-associated mucous membrane

The terminology relating to the developing ovarian follicle has been expanded to include the primordial, primary, secondary and Graafian follicle. The applicable parts have also been added and rationalized so it is possible to code the individual components of the different follicle stages.

Number of concepts edited (approx): 50

Revision of Visceral Pleura and Parietal Pleura

Content relating to the visceral pleura has been enhanced to include five layers and the parietal pleura with two layers to aid with recording pathology studies.

Number of concepts edited (approx): 14

New Concepts for Intraarticular/Extraarticular Ligaments

(body structure)|

The hierarchy 707861009|Structure of skin and/or skin-associated mucous membrane (body structure)| has been revised. The concept is a supertype for small regions where orifices make the transition from the skin surface to an internal compartment such as the mouth, urethra, anus, nose, ear and external genitalia. In addition 14811009 |Structure of mucocutaneous junction (body structure)| has been improved with the addition of subtypes 280669003 |Structure of marginal zone of palpebral conjunctiva (body structure)| and 1251500001 |Structure of anal verge (body structure)|.

Some hierarchical changes have been implemented for the supertypes of 707862002 |Structure of skin and/or mucous membrane (body structure)| and also for subtypes including 399988002 |Structure of skin and/or skin-associated mucous membrane of anogenital area (body structure)| where 87528003 |Structure of urethral meatus (body structure)| is now a subtype. Finally, the hierarchy 67149001 |Structure of urogenital region of perineum (body structure)| has been augmented by applicable subtypes to improve the classification

.

Number of concepts edited (approx): 9

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.

Clinical Finding

Revision of Hemorrhagic Cerebral Infarction

230706003 |Hemorrhagic cerebral infarction (disorder)| and subtypes have been remodeled.  An additional supertype of 50960005 |Hemorrhage (morphologic abnormality)| has been added to 88880001 |Hemorrhagic necrosis (morphologic abnormality)| to improve subsumption.

20

New Concept 1362073006 |Periarticular bone structure of joint of shoulder region (body structure)|

Revisions have been made to the bone structures of joints within the shoulder region to enhance the representations of periarticular bones in these joints. As a result, updates have been implemented to improve the modeling of fracture dislocations affecting shoulder joints.

Combinations of bone structure such as 312563005|Bone structure of rib, sternum and/or clavicle (body structure)| and 312776002|Bone structure of clavicle and/or scapula and/or humerus (body structure)| in this region have been inactivated.

Number of concepts edited (approx): 70

Description Update for 'Extremity' and 'Soft Tissues' 

Fully specified name (FSN) and preferred term (PT) have been updated from 'extremity' to 'limb' in approximately 70 body structure concepts.

Similarly, the FSN and PT for concepts referencing 'soft tissues' have been revised to 'soft tissue' in approximately 40 body structure concepts. These changes have been made to improve clarity and consistency230706003 |Hemorrhagic cerebral infarction (disorder)| is now a subtype of 5571000124103|Cerebrovascular accident with intracranial hemorrhage (disorder)|. A new synonym of 'ischemic stroke with hemorrhagic transformation' has also been added to the concept.

Number of concepts edited (approx): 12110

Revision of

40146001|Structure of cerebral cortex (body structure)|

The subtypes of 40146001 |Structure of cerebral cortex (body structure)| have been updated to include only concepts relating to the cortex gray matter. Some additional relationships have been included, for example in relation to subcategories of Brodmann areas. Two incidences of duplicate concepts have been resolved.

Number of concepts edited (approx): 50

Description Update for 'Ganglia'

The FSN and PT for 20 concepts have been updated from 'ganglia' to 'ganglion' to align with the editorial guide.

A new concept 1366040002 |Structure of autonomic ganglion (body structure)| has been added and the top-level of this sub-hierarchy has been reorganized.

Revisions have been made to the model of approximately 20 concepts to address missing and incorrect subconcepts of 57074003 |Structure of autonomic plexus ganglion (body structure)|

24526004 |Inflammatory bowel disease (disorder)| (IBD), including 34000006 |Crohn's disease (disorder)|, has been remodeled to classify as a disorder of the digestive tract. This change was made in response to submissions that, while recognizing the systemic nature of IBD,  it should be classified as a digestive system disorder. The same adjustment has been applied to its subtype, Crohn’s disease. IBD remains classified as a subtype of 56019007 |Systemic disease (disorder)|.

Extraintestinal Crohn’s disease, which includes manifestations such as arthritis, iritis, and skin conditions, occurs outside the digestive tract based on its clinical definition. It has been remodeled as being due to Crohn’s disease. In a small number of cases, two role groups have been utilized to reflect that these manifestations frequently co-occur with IBD or Crohn’s disease, as indicated by their Fully Specified Name.

No changes were necessary for ulcerative colitis, as it was already modeled as a disorder of the colon.

Number of concepts edited (approx): 20

Revision of Intestinal Obstruction

40

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.

Clinical Finding

Inactivation of 80113008|Complication of the puerperium (disorder)|

80113008|Complication of the puerperium (disorder)| has been inactivated with historical association to 362973001|Disorder of puerperium 710572000 |Intestinal obstruction co-occurrent and due to decreased peristalsis (disorder)| and 10 other functional ileus concepts (e.g., 55525008 |Paralytic ileus (disorder)|) have been remodeled to reflect that these are functional rather than mechanical intestinal obstructions. 1162567000 |Postoperative paralytic ileus (disorder)| is now a subtype of 235833007 |Postoperative ileus (disorder)|.

Number of concepts edited (approx): 11

Future changes are planned for this Content Tracker.

New Concepts for Genetic Disease

New concepts have been added for genetic disease:

• 1362108000 |Genetic intellectual disability (disorder)|
• 1359741006 |Genetic obesity disorder (disorder)|
• 1359760004 |Genetic childhood obesity disorder (disorder)|
• 1359761000 |Common polygenetic childhood obesity (disorder)|
• 1359763002 |Genetic syndromic childhood obesity (disorder)|

New Concepts for Fetal Movement

Six new concepts have been added as subtypes of 289431008 |Fetal movements present (finding)|. Three new concepts have been added under 268470003 |Fetal movements felt (finding)| and a further three under 169731002 |Fetal movements seen (finding)| to capture whether the reporter is the mother, her partner, or a healthcare professional.

Number of concepts edited (approx): 6

Update Fully Specified Name from 'Tumor' to 'Neoplasm'

Approximately 60 concepts with 'Tumor of' as the start of the FSN for descendants of 64572001 |Disease (disorder)| have had the description updated to 'Neoplasm of'.

Inactivation of 'Splinter of X' Concepts

Concepts that represent 'splinter of <x>, without major open wound' and 'splinter of <x>, without major open wound, infected' are classification constructs. These concepts have been inactivated with historical associations to the base concept. Where required, new 'base' concepts have been created.

Procedure

Revision of Endoscopic Ultrasound

447793000 |Endoscopic ultrasonography of mediastinum (procedure)| has been inactivated.

These changes have been made to complete this content tracker.

A new qualifier value has been added 1363035004 |Maternal intrapartum period and/or postpartum (qualifier value)|

Remodel 784289008 |Nerve palsy (disorder)| and Inactivation of 255324009|Movement (observable entity)|

784289008|Nerve palsy (disorder)| has been remodeled to reflect a more generalized concept.  The published modeling limited descendants to be designated by "gross movements of body and limbs".  The concept has been updated to involve movement in general to account for disorders such as facial palsy. This has resulted in a number of concepts being moved directly under 784289008|Nerve palsy (disorder)|. 

255324009|Movement (observable entity)| has been inactivated with reason duplicate and historical association to 363847004|Movement observable (observable entity)|. 

Update Descriptions for 392570002|Blood pressure finding (finding)| and Descendants

Descendants of 392570002 |Blood pressure finding (finding)| which include 'decreased,' 'increased,' 'normal,' 'abnormal' etc. in the FSN have been updated as follows:

• FSN changed to 'below reference range,' 'above reference range,' 'within reference range,' or ''outside reference range.'
• Descriptions with 'decreased,' 'increased,' 'normal,' 'abnormal', etc. retained as acceptable synonyms.
• Modeling of the Has interpretation (attribute) value updated to 281300000 |Below reference range (qualifier value)|, 281302008 |Above reference range (qualifier value)|, 281301001 |Within reference range (qualifier value)|, or 394844007 |Outside reference range (qualifier value)|.

These changes are consistent with the rationale from previous work in updating the measurement findings content. Please see this briefing note and the 'Measurement findings' section of the Editorial Guide.

Number of concepts edited (approx):

80

Revision

B-mode ultrasound, also known as brightness mode ultrasound, is a technique for generating two-dimensional grayscale images. B-scan ultrasound is the application of B-mode ultrasound, often used in areas such as ophthalmology, where it provides cross-sectional imaging of ocular and orbital structures. Since B-scan directly uses B-mode ultrasound it has now been defined using 399009009 |B mode ultrasound (qualifier value)|, ensuring consistency and interoperability.

Number of concepts edited (approx): 23

Radiographic Imaging

Work is progressing for this content tracker for information please see the informational briefing note here.   

Observable Entity

Revision of Assessment Scale Score

Concepts that are subtypes of 363788007 |Clinical history/examination observable (observable entity)| and contain the word ‘score’ that are not also subtypes of 782487009 |Assessment score (observable entity)|, have had 782487009 |Assessment score (observable entity)| added as another supertype.

Number of concepts edited (approx): 525

Inactivation and Replacement of 284937000 |Ability to sit on toilet (observable entity)| and Related Finding Concepts

The concept 284937000 |Ability to sit on toilet (observable entity)| and related finding concepts e.g. 284938005 |Able to sit on toilet (finding)| are ambiguous as they could be interpreted to mean the ability to maintain a sitting position on a toilet seat or the ability to sit down on a toilet seat. These concepts have been inactivated and replaced with new concepts:

• Ability to maintain sitting position on toilet seat (observable entity)
• Ability to sit down on toilet seat (observable entity)

Relevant finding concepts e.g. Able to maintain sitting position on toilet seat (finding) have also been added.

Pharmaceutical/Biologic Product

Inactivation of Paratyphoid Vaccine

Concepts referencing a stand-alone paratyphoid vaccination have been inactivated. There is currently no vaccine to prevent paratyphoid fever, and standalone paratyphoid vaccines are unlikely to be widely adopted.

4 concepts inactivated:

• 83798008 |Paratyphoid fever vaccination (procedure)|
• 428601009 |Paratyphoid vaccine (medicinal product)|
• 192707002 |Post paratyphoid vaccination encephalitis (disorder)|
• 219079000 |Adverse reaction to component of paratyphoid vaccine (disorder)|

Number of concepts edited (approx): 4

Situation With Explicit Context

Revision of Personal History of Primary Malignant Neoplasm

Since their creation (primarily in 2005), Personal history of primary malignant neoplasm of X (situation) concepts have consistently represented a history of a primary malignant neoplasm. As a result, the non-synonymous 'malignant neoplasm' preferred term (PT) and synonym have been inactivated for ten situation concepts. The concepts have been changed from 'personal history of' to 'history of' in the new descriptions.

These descriptions may have originated from historical ICD clinical coding rules, which assumes that a malignancy unspecified as primary or metastatic is classified as primary.

Number of concepts edited (approx): 10

Qualifier Value

New Semantic Tag

A new semantic tag has been added:

• 540091010000105| Calculation (calculation)|

The new concept is a descendant of (qualifier value). This concept will enable representation of concepts that are derived from calculations on other observations (e.g., “Anion gap in blood,”  “Anion gap in urine”) with a relationship of Component (attribute) and value from the (calculation) sub-hierarchy.

Collaboration/Harmonization Agreements

Convergent Medical Terminology (CMT)

80 new CMT concepts have been added with a focus on ophthalmology.

Orphanet

Working in collaboration with Orphanet 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.

Work is ongoing to annotate content added for the Orphanet project with attribution to Inserm Orphanet. It is expected this work will be completed for the May 2025 International Edition release.

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

Gravity

Work for this project is ongoing.

Nursing

Work for this project is ongoing.

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 

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)|.

Further information about the project is available here

Internal Quality Improvement

Machine Readable Concept Model (MRCM) Changes

There have been two changes for the MRCM in the April 2025 International Edition.

of 1418361000168101 |Keratinocytic epidermal carcinoma of skin (disorder)|

Keratinocytic epidermal carcinoma of skin originates in the epidermis and includes both squamous cell carcinoma (SCC) and basal cell carcinoma (BCC).The primitive concept 1418361000168101 |Keratinocytic epidermal carcinoma of skin (disorder)| has been revised, now incorporating two General Concept Inclusion (GCI) axioms - one for basal cell carcinoma and one for squamous cell carcinoma. This update ensures that all SCC and BCC skin disorder concepts are correctly subsumed as subtypes and are modeled with a proximal primitive parent.

Number of concepts edited (approx): 3

Inactivation of 42571002|Failed induction of labor (disorder)| and Descendants

The following concepts have been inactivated and new concepts added to the situation with explicit context hierarchy as subtypes of 103709008 |Failed attempted procedure (situation)|

• 42571002 |Failed induction of labor (disorder)|
• 90188009 |Failed mechanical induction (disorder)|
• 77854008 |Failed medical induction of labor (disorder)|
• 91484005 |Failure of induction of labor by oxytocic drugs (disorder)|

A new concept has been added 1365933005 |Mechanical induction of labor (procedure)| as the missing third subtype of 236958009 |Induction of labor (procedure)| this is after review of usage statistics for the existing concepts.

Procedure

Revision of 120001005|Testis excision (procedure)| Hierarchy

A new concept has been added: 1365727008 |Partial excision of bilateral testes (procedure)|.

Two new body structure concepts have been added:

• 1365725000 |Part of left testis (body structure)|
• 1365724001 |Part of right testis (body structure)|

Additional changes have been made for the values of 'Procedure site - Direct' for the concepts referring to partial excision of testis within the 120001005 |Testis excision (procedure)| hierarchy

Number of concepts edited (approx): 20

Inactivation of 47696003|Anastomosis of intestine, large-to-anus (procedure)|

47696003 |Anastomosis of intestine, large-to-anus (procedure) has been inactivated and replaced by a new concept 1363475000 |Anastomosis of colon to anal canal (procedure)|.

Radiographic Imaging

Work is progressing for this content tracker for information please see the informational briefing note here.   

Collaboration/Harmonization Agreements

Convergent Medical Terminology (CMT)

212 new CMT concepts have been added for the May 2025 release with the main focus areas being injuries, ophthalmology and obstetric and gynecology domains.

Orphanet

Working in collaboration with Orphanet 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.

Work has been completed in the May 2025 release to annotate content added for the Orphanet project with attribution to Inserm Orphanet. 

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

Gravity

Work for this project is ongoing.

Nursing

Work for this project is ongoing.

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 

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)|.

Further information about the project is available here

Internal Quality Improvement

Machine Readable Concept Model (MRCM) Changes

The following changes have been made for MRCM in the May 2025 International Edition.

• Update to Attribute Cardinality: The following attributes used in modeling << 363787002 |Observable entity (observable entity) have had cardinality updated from 0..1 to 0..*. The changes will support modeling observable entity concepts where two (or more) types of observations are modeled in one concept and the result is reported in one value.

• • 370134009 |Time aspect (attribute)|
  • 704323007 |Process duration (attribute)|
  • 370130000 |Property (attribute)|
  • 246514001 |Units (attribute)|

• Description update
  • 26716007|Qualitative (qualifier value)| FSN and PT updated to 26716007 |Qualitative value (qualifier value)|
  • 30766002|Quantitative (qualifier value)| FSN and PT updated to 30766002 |Quantitative value (qualifier value)|
  • 103392008|Semi-quantitative (qualifier value)| FSN and PT updated to 103392008 |Semi-quantitative value (qualifier value)|

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

Please see Early Visibility Release Notifications for future planned changes to MRCM.

Annotation Reference Set

The addition of content for the Annotations refset was commenced in the July 2024 International Edition release and is ongoing for attribution of text definition to organizations with in scope content that is part of a collaboration agreement, starting with Inserm Orphanet.  

SNOMED CT derived products

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.

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 constrained to subtypes of 404684003 |Clinical finding (finding)|, 272379006 |Event (event)|, and 243796009 |Situation with explicit context (situation)|. The target classification used is the ICD-10 WHO version 2016 (https://icd.who.int/browse10/2016/en#/).

Mapped content for April May 2025 release

The map provided for this release has been updated and represents a complete map from the April May 2025 release of the SNOMED CT International Edition to the ICD-10 WHO version 2016.

This includes:

• Addition of 407 522 new mapped concepts

• Updates to 334 538 existing mapped concepts
• Retirement of 110 94 mapped concepts

The SNOMED CT to ICD-O morphology map has zero (0) additions for this release.

We welcome feedback on any issues that users may detect when deploying the map. Issues can be reported to mapping@snomed.org.

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.

Technical notes

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:

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:

Technical updates

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.

 Proposal to increase the maximum length of Description Types

Please find below the link to the recent announcement on the proposal to increase the limit of characters allowed in Descriptions:

• https://confluence.ihtsdotools.org/pages/viewpage.action?pageId=238158325

A community consultation was launched to solicit feedback on a proposal to increase the size limits of SNOMED CT concept descriptions to 4096 from the current limit of 255 characters. While this change does not represent a modification of the existing specification, it could be disruptive to implementers who have coded fixed length limits into their systems.  

Please read the full proposal, along with the latest Q&A blog post which details the proposed change, its potential benefits, the feedback process and timelines, and the issues that may need to be considered in such an update:

• https://confluence.ihtsdotools.org/mag/community-consultations/snomed-international-proposal-to-increase-description-length-limit
• https://www.snomed.org/news/blog%3A-snomed-international-seeks-community-feedback-on-proposed-description-character-limit-increase

As always, SNOMED International greatly appreciated all feedback provided before the deadline (which was Dec 31, 2024).  A summary of the feedback will be collated and disseminated in 2025, alongside a plan for the transition.

Early visibility of impending changes in the upcoming 2025 Monthly International Edition releases

Please see the Early Visibility Release Notifications Confluence page for details of forthcoming changes.