2026 ICD-10-CM Diagnosis Code K61.31Horseshoe abscess

ICD-10-CM Codes›K00–K95›K55-K64›K61

ICD-10-CM K61.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K61.31 is a billable ICD-10-CM diagnosis code for horseshoe abscess. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 393 through 395. Coders also document this condition as transsphincteric anal fistula. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Anal and rectal conditions and Peritonitis and intra-abdominal abscess.

Code Identity

ICD-10-CM Code
K61.31
Billable Status
Yes — Valid for Submission
Code Describes
Horseshoe abscess
Short Description
Horseshoe abscess
Same as the full description in the CMS dataset.
Parent Code
K61.3
Ischiorectal abscess

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK55-K64Other diseases of intestines
CategoryK61Abscess of anal and rectal regions
This CodeK61.31Horseshoe abscess

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Transsphincteric anal fistula
  • Transsphincteric anal horseshoe fistula

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.

    • Abscess(connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic)
      • horseshoe

Clinical ClassificationClinical

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

CCSR DIG015
Anal and rectal conditions
Default principal diagnosis: inpatient No · outpatient No
CCSR DIG016
Peritonitis and intra-abdominal abscess
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Abscess

An abscess is a pocket of pus. You can get an abscess almost anywhere in your body. When an area of your body becomes infected, your body's immune system tries to fight the infection. White blood cells go to the infected area, collect within the damaged tissue, and cause inflammation. During this process, pus forms.

Read the full article at MedlinePlus

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

Code History & ChangesHistory

Replacement K61.31 replaces the following previously assigned code(s):

  • K61.3 - Ischiorectal abscess
FY 2019AddedAdded to the ICD-10-CM code setEffective October 1, 2018.
FY 2020–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About K61.31Overview

Is K61.31 (Ischiorectal abscess) a billable code?

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

What MS-DRG does K61.31 group to?

When horseshoe abscess is the principal diagnosis on an inpatient stay, it groups to MS-DRG 393, 394, 395, with relative weights from 0.6490 to 1.5993 depending on complications. Higher weights mean higher Medicare reimbursement.

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.