2026 ICD-10-CM Diagnosis Code A74.81Chlamydial peritonitis

ICD-10-CM Codes›A00–B99›A70-A74›A74

ICD-10-CM A74.81
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A74.81 is a billable ICD-10-CM diagnosis code for chlamydial peritonitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 865 through 866. Coders also document this condition as chlamydial perihepatitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Peritonitis and intra-abdominal abscess.

Code Identity

ICD-10-CM Code
A74.81
Billable Status
Yes — Valid for Submission
Code Describes
Chlamydial peritonitis
Short Description
Chlamydial peritonitis
Same as the full description in the CMS dataset.
Parent Code
A74.8
Other chlamydial diseases

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA70-A74Other diseases caused by chlamydiae
CategoryA74Other diseases caused by chlamydiae
This CodeA74.81Chlamydial peritonitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chlamydial perihepatitis
  • Chlamydial peritonitis
  • Fitz-Hugh-Curtis syndrome
  • Infection of peritoneum caused by Chlamydia trachomatis
  • Inflammation of pelvis caused by Chlamydia trachomatis
  • Pelvic peritonitis
  • Perihepatitis
  • Perihepatitis caused by Chlamydia trachomatis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • 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

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient No · outpatient No
CCSR DIG016
Peritonitis and intra-abdominal abscess
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Pelvic Peritonitis

    inflammation of the peritoneum surrounding the pelvic organs.

Patient EducationClinical

Bacterial Infections

Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

The full article covers:

  • What are bacteria?
  • How do bacterial infections spread?
  • What are the treatments for bacterial infections?
  • Can bacterial infections be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A74.81 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
079.88 Oth spcf chlamydial infc
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A74.81Overview

Is A74.81 (Other chlamydial diseases) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report chlamydial peritonitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A74.81 group to?

When chlamydial peritonitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 865, 866, with relative weights from 0.8696 to 1.4983 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of A74.81?

Under the General Equivalence Mappings, chlamydial peritonitis converts to ICD-9-CM 079.88 (oth spcf chlamydial infc). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.