This is the CodeSystem that contains all the codes in Treatment Reason (https://www.ehealth.fgov.be/standards/fhir/nihdi-terminology/CodeSystem/be-cs-treatment-reason) and Treatment Reason (https://www.ehealth.fgov.be/standards/fhir/nihdi-terminology/CodeSystem/be-cs-treatment-reason). E.g. what you have to deal with if you get resources containing codes in either of them