General Surgery Coding Alert

Question: What do "NEC" and "NOS" mean in diagnosis coding? How should I choose between them?

Florida Subscriber

Answer: ICD-9 uses the abbreviations NEC and NOS to denote diagnoses "not elsewhere classified" and "not otherwise specified." NEC is equivalent to using an "other" code selection, and NOS is equivalent to using an "unspecified" code selection.

Think of NEC as a lack of specificity in ICD-9. Your surgeon provides specific findings, but ICD-9 does not list a specific code that describes the diagnosis. On the other hand, consider NOS the fault of insufficient documentation, which does not provide enough information to assign a more specific diagnosis code.

An example of when you would use an NEC code: Your surgeon specifies "Atony colon disorder." You look in the 564 category, Functional digestive disorders, not elsewhere classified, for the appropriate code. Codes 564.0-564.7 do not list the manifestation that the physician indicated, so you should report 564.89 (Other functional disorders of intestine), which includes "Atony of colon."

But suppose the surgeon notes simply, "gastric ulcer." The physician doesn't specify acute or chronic, so you should report 531.9x, which includes "unspecified as acute or chronic, without mention of hemorrhage or perforation."