A09 vs K52.9
A09 and K52.9 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported. The distinction is infectious vs non-infective origin.
Infectious gastroenteritis and colitis, unspecified
- Chapter 1
- Certain infectious and parasitic diseases
- Section
- A00-A09
- Infectious colitis NOS
- Infectious enteritis NOS
- Infectious gastroenteritis NOS
- Dysentery, dysenteric (catarrhal) (diarrhea) (epidemic) (hemorrhagic) (infectious) (sporadic) (tropical)
- Diarrhea, diarrheal › dysenteric
- Diarrhea, diarrheal › endemic
- Diarrhea, diarrheal › epidemic
- Diarrhea, diarrheal › infectious
Noninfective gastroenteritis and colitis, unspecified
- Chapter 11
- Diseases of the digestive system
- Section
- K50-K52
- Colitis NOS
- Enteritis NOS
- Gastroenteritis NOS
- Ileitis NOS
- Jejunitis NOS
- Sigmoiditis NOS
- Cecitis
- Colitis (acute) (catarrhal) (chronic) (noninfective) (hemorrhagic)
- Enteritis (acute) (diarrheal) (hemorrhagic) (noninfective)
- Enterocolitis
- Gastroenteritis (acute) (chronic) (noninfectious)
These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027