K31.B vs Q40.0
K31.B and Q40.0 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 K31.B
congenital pyloric stenosis (Q40.0)
K31.B
Hypertrophic pyloric stenosis, in childhood
Billable
- Chapter 11
- Diseases of the digestive system
- Section
- K20-K31
Use when the record says
- Infantile hypertrophic pyloric stenosis
- Pediatric hypertrophic pyloric stenosis
- Pediatric pyloric stenosis
Indexed under
- Stenosis, stenotic › pylorus › in childhood (cicatricial)
- Stenosis, stenotic › pylorus › infantile (cicatricial)
- Stenosis, stenotic › pylorus › pediatric (cicatricial)
- Stricture › pylorus › infantile
Q40.0
Congenital hypertrophic pyloric stenosis
Billable
- Chapter 17
- Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders
- Section
- Q38-Q45
Use when the record says
- Congenital constriction
- Congenital hypertrophy
- Congenital spasm
- Congenital stenosis
- Congenital stricture
Indexed under
- Achalasia › pylorus (cardia) (esophagus)
- PylorospasmNEC › congenital (reflex)
- PylorospasmNEC › newborn (reflex)
- Constriction › pylorus › congenital
- Constriction › pylorus › newborn
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