2026 ICD-10-CM Diagnosis Code K59.9Functional intestinal disorder, unspecified

ICD-10-CM Codes›K00–K95›K55-K64›K59

ICD-10-CM K59.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K59.9 is a billable ICD-10-CM diagnosis code for functional intestinal disorder, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 391 through 392. Coders also document this condition as anorectal dysfunction due to pelvic organ prolapse. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified gastrointestinal disorders.

Code Identity

ICD-10-CM Code
K59.9
Billable Status
Yes — Valid for Submission
Code Describes
Functional intestinal disorder, unspecified
Short Description
Functional intestinal disorder, unspecified
Same as the full description in the CMS dataset.
Parent Code
K59
Other functional intestinal disorders

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK55-K64Other diseases of intestines
CategoryK59Other functional intestinal disorders
This CodeK59.9Functional intestinal disorder, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anorectal dysfunction due to pelvic organ prolapse
  • Bowel dysfunction
  • Congenital functional disorders of the small intestine
  • Functional anorectal disorder
  • Functional disorder of gastrointestinal tract
  • Functional disorder of gastrointestinal tract in childhood
  • Functional disorder of intestine

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.

    • Complaint
      • bowel, functional
    • Complaint
      • intestine, functional
    • Disease, diseased
      • bowel
        • functional
    • Disease, diseased
      • colon
        • functional
    • Disease, diseased
      • gastrointestinal (tract)
        • functional
    • Disease, diseased
      • intestine
        • functional
    • Disorder(of)
      • intestine, intestinal
        • functional NEC
    • Distress
      • intestinal (functional) NOS
    • Dysfunction
      • colon
    • Dysfunction
      • rectum
    • Syndrome
      • functional
        • bowel
    • Upset
      • intestinal (large) (small)

Clinical ClassificationClinical

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

CCSR DIG025
Other specified and unspecified gastrointestinal disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Digestive Diseases

When you eat, your body breaks food down to a form it can use to build and nourish cells and provide energy. This process is called digestion.

Read the full article at MedlinePlus

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

Convert K59.9 to ICD-9-CMHistory

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

ICD-9-CM
564.9 Funct dis intestine NOS
Exact Match The mapping is direct, with no qualifiers.

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 K59.9Overview

Is K59.9 (Other functional intestinal disorders) a billable code?

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

What MS-DRG does K59.9 group to?

When functional intestinal disorder, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 391, 392, with relative weights from 0.7796 to 1.2683 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of K59.9?

Under the General Equivalence Mappings, functional intestinal disorder, unspecified converts to ICD-9-CM 564.9 (funct dis intestine NOS). The mapping is a direct match.

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.