Excludes1 pair

K65- vs P78.1

K65 and P78.1 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 official note, declared on K65
neonatal peritonitis (P78.0-P78.1)
K65

Peritonitis

Not billable
Chapter 11
Diseases of the digestive system
Section
K65-K6A
P78.1

Other neonatal peritonitis

Billable
Chapter 16
Certain conditions originating in the perinatal period
Section
P76-P78
Use when the record says
  • Neonatal peritonitis NOS
Indexed under
  • Peritonitis › congenital
  • Peritonitis › neonatal

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