2026 ICD-10-CM Diagnosis Code K52.831Collagenous colitis

ICD-10-CM Codes›K00–K95›K50-K52›K52

ICD-10-CM K52.831
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K52.831 is a billable ICD-10-CM diagnosis code for collagenous colitis. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Noninfectious gastroenteritis.

K52.831 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 67 for payment year 2026.

Code Identity

ICD-10-CM Code
K52.831
Billable Status
Yes — Valid for Submission
Code Describes
Collagenous colitis
Short Description
Collagenous colitis
Same as the full description in the CMS dataset.
Parent Code
K52.83
Microscopic colitis

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK50-K52Noninfective enteritis and colitis
CategoryK52Other and unspecified noninfective gastroenteritis and colitis
This CodeK52.831Collagenous colitis

Medicare Risk Adjustment (HCC)Billing

K52.831 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model, but it maps to payment categories in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
no payment category in the model that pays 100% of MA risk scores
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Part D (RxHCC)
RxHCC 67 — Inflammatory Bowel Disease
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Collagenous colitis
  • Microscopic colitis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR DIG022
Noninfectious gastroenteritis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Collagenous Colitis

    a type of microscopic colitis of unknown etiology. it is characterized by the presence of collagen deposits in the lamina propria of the colonic mucosa. patients present with chronic watery diarrhea. colonoscopy reveals normal-appearing mucosa. the diagnosis is made with the microscopic examination of the colonic biopsy samples.

  • Microscopic Colitis

    inflammation of the colon that is only apparent by microscopic examination.

Patient EducationClinical

Colonic Diseases

Your colon, also known as the large intestine, is part of your digestive system. It's a long, hollow tube at the end of your digestive tract where your body makes and stores stool. Many disorders affect the colon's ability to work properly. Some of these include:

Read the full article at MedlinePlus

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

Convert K52.831 to ICD-9-CMHistory

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

ICD-9-CM
558.9 Noninf gastroenterit NEC
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement K52.831 replaces the following previously assigned code(s):

  • K52.89 - Other specified noninfective gastroenteritis and colitis
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 K52.831Overview

What is the ICD-10 code for collagenous colitis?

The ICD-10-CM code for collagenous colitis is K52.831 (sometimes written as K52831). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is K52.831 (Microscopic colitis) a billable code?

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

What MS-DRG does K52.831 group to?

When collagenous colitis 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 K52.831?

Under the General Equivalence Mappings, collagenous colitis converts to ICD-9-CM 558.9 (noninf gastroenterit NEC). The mapping is approximate, so confirm the match fits the documentation.

Does K52.831 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: K52.831 maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 67 (Inflammatory Bowel Disease).