2026 ICD-10-CM Diagnosis Code K51.319Ulcerative (chronic) rectosigmoiditis with unspecified complications

ICD-10-CM Codes›K00–K95›K50-K52›K51

ICD-10-CM K51.319
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K51.319 is a billable ICD-10-CM diagnosis code for ulcerative (chronic) rectosigmoiditis with unspecified complications. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 385 through 387. Coders also document this condition as complication due to chronic ulcerative proctitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Regional enteritis and ulcerative colitis.

Code Identity

ICD-10-CM Code
K51.319
Billable Status
Yes — Valid for Submission
Code Describes
Ulcerative (chronic) rectosigmoiditis with unspecified complications
Short Description
Ulcerative (chronic) rectosigmoiditis w unsp complications
Parent Code
K51.31
Ulcerative (chronic) rectosigmoiditis with complications

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK50-K52Noninfective enteritis and colitis
CategoryK51Ulcerative colitis
This CodeK51.319Ulcerative (chronic) rectosigmoiditis with unspecified complications

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Complication due to chronic ulcerative proctitis
  • Complication due to chronic ulcerative rectosigmoiditis

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.

    • Rectosigmoiditis
      • ulcerative (chronic)
        • with
          • complication

Clinical ClassificationClinical

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

CCSR DIG011
Regional enteritis and ulcerative colitis
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Ulcerative Colitis

Ulcerative colitis (UC) is a disease that causes inflammation and sores, called ulcers, in the lining of the rectum and colon. It is one of a group of diseases called inflammatory bowel disease.

Read the full article at MedlinePlus

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

Convert K51.319 to ICD-9-CMHistory

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

ICD-9-CM
556.3 Ulcertve prctosigmoidtis
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 K51.319Overview

Is K51.319 (Ulcerative (chronic) rectosigmoiditis with complications) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report ulcerative (chronic) rectosigmoiditis with unspecified complications on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does K51.319 group to?

When ulcerative (chronic) rectosigmoiditis with unspecified complications is the principal diagnosis on an inpatient stay, it groups to MS-DRG 385, 386, 387, with relative weights from 0.6813 to 1.5823 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of K51.319?

Under the General Equivalence Mappings, ulcerative (chronic) rectosigmoiditis with unspecified complications converts to ICD-9-CM 556.3 (ulcertve prctosigmoidtis). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.