This is the ValueSet that contains all the codes in US Core Non Laboratory Codes (http://hl7.org/fhir/us/core/ValueSet/us-core-diagnosticreport-report-and-note-codes) and LOINC Diagnostic Report Codes (http://hl7.org/fhir/ValueSet/report-codes). E.g. what you have to deal with if you get resources containing codes in either of them