2026 ICD-10-CM Diagnosis Code M25.18Fistula, other specified site

ICD-10-CM Codes›M00–M99›M20-M25›M25

ICD-10-CM M25.18
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M25.18 is a billable ICD-10-CM diagnosis code for fistula, other specified site. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 555 through 556. Coders also document this condition as fistula of vertebral joint. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified joint disorders.

Code Identity

ICD-10-CM Code
M25.18
Billable Status
Yes — Valid for Submission
Code Describes
Fistula, other specified site
Short Description
Fistula, other specified site
Same as the full description in the CMS dataset.
Parent Code
M25.1
Fistula of joint

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM25Other joint disorder, not elsewhere classified
This CodeM25.18Fistula, other specified site

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Fistula of vertebral joint

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Fistula, vertebrae

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.

    • Fistula(cutaneous)
      • joint
        • specified joint NEC
    • Fistula(cutaneous)
      • joint
        • vertebrae

Clinical ClassificationClinical

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

CCSR MUS007
Other specified joint disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Fistulas

A fistula is an abnormal connection between two parts inside of the body. Fistulas may develop between different organs, such as between the esophagus and the windpipe or the bowel and the vagina. They can also develop between two blood vessels, such as between an artery and a vein or between two arteries.

Read the full article at MedlinePlus

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

Convert M25.18 to ICD-9-CMHistory

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

ICD-9-CM
719.88 Joint dis NEC-oth jt
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 M25.18Overview

Is M25.18 (Fistula of joint) a billable code?

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

What MS-DRG does M25.18 group to?

When fistula, other specified site is the principal diagnosis on an inpatient stay, it groups to MS-DRG 555, 556, with relative weights from 0.8306 to 1.3218 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M25.18?

Under the General Equivalence Mappings, fistula, other specified site converts to ICD-9-CM 719.88 (joint dis NEC-oth jt). 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.