Gastroenterology Coding Alert

Question: What do "NOS" and "NEC" mean in diagnosis coding? How do I tell the difference between them?
Florida Subscriber

Answer: ICD-9 uses the abbreviations NOS and NEC to denote diagnoses "not otherwise specified" and "not elsewhere classified," respectively.

Consider NOS a matter of insufficient documentation, which does not provide enough information to assign a more specific diagnosis code.

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 gastroenterologist provides specific findings, but ICD-9 does not list a specific code that describes her diagnosis.

NOS example: Suppose the referral notes simply, "Crohn's." The physician doesn't specify small intestine or large, so you should report 555.9 (Regional enteritis; unspecified site) which includes "Crohn's disease NOS."

NEC example: Your gastroenterologist 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."