2026 ICD-10-CM Diagnosis Code K31.A13Gastric intestinal metaplasia without dysplasia, involving the fundus

ICD-10-CM Codes›K00–K95›K20-K31›K31

ICD-10-CM K31.A13
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K31.A13 is a billable ICD-10-CM diagnosis code for gastric intestinal metaplasia without dysplasia, involving the fundus. 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 gastric intestinal metaplasia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified disorders of stomach and duodenum.

Code Identity

ICD-10-CM Code
K31.A13
Billable Status
Yes — Valid for Submission
Code Describes
Gastric intestinal metaplasia without dysplasia, involving the fundus
Short Description
Gastric intestnl metaplasia without dysplasia, w the fundus
Parent Code
K31.A1
Gastric intestinal metaplasia without dysplasia

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK20-K31Diseases of esophagus, stomach and duodenum
CategoryK31Other diseases of stomach and duodenum
This CodeK31.A13Gastric intestinal metaplasia without dysplasia, involving the fundus

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Gastric intestinal metaplasia
  • Intestinal metaplasia of fundus of stomach

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.

    • Metaplasia
      • gastric intestinal
        • without dysplasia
          • involving
            • fundus

Clinical ClassificationClinical

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

CCSR DIG008
Other specified and unspecified disorders of stomach and duodenum
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Gastric Intestinal Metaplasia

    a morphologic finding indicating the replacement of part of the gastric mucosal epithelium with intestinal-type epithelium. using immunohistochemical staining, gastric intestinal metaplasia is classified as complete or incomplete. complete intestinal metaplasia is defined by the decreased expression of gastric mucins and expression of the intestinal mucin muc2. incomplete intestinal metaplasia is defined by the co-expression of both gastric mucins and muc2.

  • Intestinal Metaplasia of Gastric Mucosa|Gastric Intestinal Metaplasia

    a morphologic finding indicating the replacement of part of the gastric mucosal epithelium with intestinal-type epithelium. using immunohistochemical staining, gastric intestinal metaplasia is classified as complete or incomplete. complete intestinal metaplasia is defined by the decreased expression of gastric mucins and expression of the intestinal mucin muc2. incomplete intestinal metaplasia is defined by the co-expression of both gastric mucins and muc2.

Code History & ChangesHistory

Replacement K31.A13 replaces the following previously assigned code(s):

  • K31.89 - Other diseases of stomach and duodenum
FY 2022AddedAdded to the ICD-10-CM code setEffective October 1, 2021.
FY 2023–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About K31.A13Overview

Is K31.A13 (Gastric intestinal metaplasia without dysplasia) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report gastric intestinal metaplasia without dysplasia, involving the fundus on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does K31.A13 group to?

When gastric intestinal metaplasia without dysplasia, involving the fundus 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.

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.