ICD-10-CM 2027 diagnosis code

K66Other disorders of peritoneum

Not billable — use a more specific code

K66 is a header code, so it can't be reported by itself. Choose one of the 4 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About K66

K66 is the ICD-10-CM diagnosis code for other disorders of peritoneum. It belongs to block K65-K6A (diseases of peritoneum, retroperitoneum and pelvis) and chapter 11 (diseases of the digestive system). It is a header code, so it can't be reported by itself; one of its 4 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: K66.0 ((postinfection)), K66.1 (Hemoperitoneum), K66.8 (peritoneum) and K66.9 (unspecified).

The conditions in its Excludes2 note aren't part of K66, but may be coded alongside it if the patient has both: ascites (R18.-) and peritoneal effusion (chronic) (R18.8).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under K66

Coding notes

Excludes2Not included here — may be reported together if both conditions exist

ascites (R18.-)
peritoneal effusion (chronic) (R18.8)

Notes that apply from higher levels

Instructions written at a parent level also apply to K66.

Broader instructions also apply from Chapter 11: Diseases of the digestive system.

Code history

2016
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2021
2022
2023
2024
2025
2026
2027

FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
No changes since FY2016.

Common questions about K66

Is K66 billable?: No. K66 is a header code. Report one of its more specific subcodes instead.