2026 ICD-10-CM Diagnosis Code K51.30Ulcerative (chronic) rectosigmoiditis without complications

ICD-10-CM Codes›K00–K95›K50-K52›K51

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

K51.30 is a billable ICD-10-CM diagnosis code for ulcerative (chronic) rectosigmoiditis without 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Regional enteritis and ulcerative colitis.

Code Identity

ICD-10-CM Code
K51.30
Billable Status
Yes — Valid for Submission
Code Describes
Ulcerative (chronic) rectosigmoiditis without complications
Short Description
Ulcerative (chronic) rectosigmoiditis without complications
Same as the full description in the CMS dataset.
Parent Code
K51.3
Ulcerative (chronic) rectosigmoiditis

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK50-K52Noninfective enteritis and colitis
CategoryK51Ulcerative colitis
This CodeK51.30Ulcerative (chronic) rectosigmoiditis without complications

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute left-sided ulcerative colitis
  • Acute proctitis
  • Acute ulcerative colitis
  • Acute ulcerative proctitis
  • Acute ulcerative rectosigmoiditis
  • Chronic left-sided ulcerative colitis
  • Chronic proctocolitis
  • Chronic ulcerative proctitis
  • Chronic ulcerative rectosigmoiditis
  • Left sided ulcerative colitis
  • Left sided ulcerative colitis in remission
  • Proctocolitis
  • Proctosigmoiditis
  • Sigmoid colon ulcer
  • Ulcerative colitis in remission
  • Ulcerative proctitis
  • Ulcerative proctitis in remission
  • Ulcerative proctocolitis
  • Ulcerative rectosigmoiditis in remission

Tabular List NotesGuidance

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

Inclusion Terms

  • Ulcerative (chronic) rectosigmoiditis NOS

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)

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

Clinical InformationClinical

  • Proctocolitis

    inflammation of the rectum and the distal portion of the colon.

  • Ulcerative Proctitis

    a form of ulcerative colitis where the inflammation is confined to the rectum.

  • Proctosigmoiditis

    inflammation of the sigmoid colon and rectum.

  • Proctocolitis

    inflammation of the rectum and colon.

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 K51.30 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 K51.30Overview

Is K51.30 (Ulcerative (chronic) rectosigmoiditis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report ulcerative (chronic) rectosigmoiditis without complications on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does K51.30 group to?

When ulcerative (chronic) rectosigmoiditis without 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 K51.30?

Under the General Equivalence Mappings, ulcerative (chronic) rectosigmoiditis without 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.