I would also like to point out that the hierarchy in SNOMED (and any other ontology) is built with a purpose. That purpose does not always overlap with the use case you need. Value sets are groups of codes/concepts that are intended to mean the same thing, or to identify a concept for a process like cohorting patients or triggering CDSS. Descendants of a single SNOMED code do not always meet this requirement. For example, there are SNOMED codes that imply that a patient has Diabetes that do not fall under the SNOMED disorder for Diabetes Mellitus. Previously, Sigmoidoscopy was a child of Colonoscopy (as the sigmoid is part of the colon). However, the CDSS rules for screening endoscopy are different whether the patient has only had a sigmoidoscopy versus a full colonoscopy so you don’t want the descendants of colonoscopy to all trigger the colonoscopy rule.
So, what I am saying is that CDSS rules need to consider the use of curated value sets for concepts and not just assume that single code hierarchical queries are sufficient.