K59.3 vs Q43.1
K59.3 and Q43.1 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on K59.3
congenital megacolon (aganglionic) (Q43.1)
K59.3
Megacolon, not elsewhere classified
Not billable
- Chapter 11
- Diseases of the digestive system
- Section
- K55-K64
Use when the record says
- Dilatation of colon
Q43.1
Hirschsprung's disease
Billable
- Chapter 17
- Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders
- Section
- Q38-Q45
Use when the record says
- Aganglionosis
- Congenital (aganglionic) megacolon
Indexed under
- Aganglionosis (bowel) (colon)
- Hirschsprung's disease or megacolon
- Macrocolon
- Megacolon › congenital, congenitum (acquired) (functional) (not Hirschsprung's disease) (in)
- Megacolon › Hirschsprung's (acquired) (functional) (not Hirschsprung's disease) (in)
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