ICD-10-CM 2027 diagnosis code
A74.81Chlamydial peritonitis
A74.81 is a valid, billable ICD-10-CM code for chlamydial peritonitis. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
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 A74.81
A74.81 is the ICD-10-CM diagnosis code for chlamydial peritonitis. It belongs to category A74 (other diseases caused by chlamydiae), block A70-A74 (other diseases caused by chlamydiae) and chapter 1 (certain infectious and parasitic diseases). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within A74.8 (other chlamydial diseases), A74.81 is specifically for chlamydial peritonitis. Related codes cover other chlamydial diseases (A74.89).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 865 (Viral Illness with MCC, relative weight 1.3485) and DRG 866 (Viral Illness without MCC, relative weight 0.8692), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.
Before ICD-10, this condition was coded in ICD-9-CM as 079.88 (other specified chlamydial infection).
Notes that apply from higher levels
Instructions written at a parent level also apply to A74.81.
Broader instructions also apply from A70-A74 Other diseases caused by chlamydiae and Chapter 1: Certain infectious and parasitic diseases.
Alphabetic index entries
4 entriesTerms in the official ICD-10-CM index that lead to A74.81.
- Chlamydia, chlamydial › peritonitis
- Fitzhugh-Curtis syndrome › due to › Chlamydia trachomatis
- Peritonitis (adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion) › chlamydial
- Syndrome › Fitzhugh-Curtis › due to › Chlamydia trachomatis
Codes whose notes reference A74.81
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 18 · Infectious and Parasitic Diseases, Systemic or Unspecified Sites
ICD-9-CM equivalent
Converter →- 079.88Other specified chlamydial infectionapproximate
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 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 A74.81
Is A74.81 billable?
- Yes. A74.81 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A74.81 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A74.81 as a principal diagnosis.
Is A74.81 a CC or MCC?
- No. A74.81 is neither a CC nor an MCC under MS-DRG v44.0.
What DRG does A74.81 group to?
- A74.81 is used in the MS-DRG v44.0 logic for MS-DRG 865 (Viral Illness with MCC) and MS-DRG 866 (Viral Illness without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for A74.81?
- The CMS General Equivalence Mappings map A74.81 to ICD-9-CM 079.88.