2026 ICD-10-CM Diagnosis Code K52.21Food protein-induced enterocolitis syndrome

ICD-10-CM Codes›K00–K95›K50-K52›K52

ICD-10-CM K52.21
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K52.21 is a billable ICD-10-CM diagnosis code for food protein-induced enterocolitis syndrome. 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 dietetic enterocolitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Allergic reactions and Noninfectious gastroenteritis.

Code Identity

ICD-10-CM Code
K52.21
Billable Status
Yes — Valid for Submission
Code Describes
Food protein-induced enterocolitis syndrome
Short Description
Food protein-induced enterocolitis syndrome
Same as the full description in the CMS dataset.
Parent Code
K52.2
Allergic and dietetic gastroenteritis and colitis

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK50-K52Noninfective enteritis and colitis
CategoryK52Other and unspecified noninfective gastroenteritis and colitis
This CodeK52.21Food protein-induced enterocolitis syndrome

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Dietetic enterocolitis
  • Dietetic jejunitis
  • Food protein-induced colitis in infant
  • Food protein-induced proctitis in infant
  • Food-protein induced enterocolitis syndrome
  • Jejunitis

Tabular List NotesGuidance

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

Inclusion Terms

  • FPIES

Use Additional Code

  • code for hypovolemic shock, if present R57.1

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.

    • Allergy, allergic(reaction) (to)
      • milk protein
        • enterocolitis syndrome
    • Colitis(acute) (catarrhal) (chronic) (noninfective) (hemorrhagic)
      • allergic
        • with
          • food protein-induced enterocolitis syndrome
    • Enteritis(acute) (diarrheal) (hemorrhagic) (noninfective)
      • allergic
        • with
          • food protein-induced enterocolitis syndrome
    • Enteritis(acute) (diarrheal) (hemorrhagic) (noninfective)
      • allergic
        • with
          • FPIES
    • FPIES(food protein-induced enterocolitis syndrome)
    • Gastroenteritis(acute) (chronic) (noninfectious)
      • allergic
        • with
          • food protein-induced enterocolitis syndrome
    • Syndrome
      • food protein-induced enterocolitis (FPIES)

Clinical ClassificationClinical

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

CCSR INJ031
Allergic reactions
Default principal diagnosis: inpatient No · outpatient No
CCSR DIG022
Noninfectious gastroenteritis
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Food Allergy

A food allergy is an abnormal immune system reaction to certain foods. Your immune system normally protects you from germs. But if you have a food allergy, your immune system mistakenly reacts to certain foods as if they were harmful. This reaction is usually mild. But in some cases, it can be serious or even life-threatening.

The full article covers:

  • What is a food allergy?
  • Who is more likely to develop a food allergy?
  • What are the symptoms of food allergies?
  • How are food allergies diagnosed?
  • What are the treatments for food allergies?

Read the full article at MedlinePlus

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

Convert K52.21 to ICD-9-CMHistory

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

ICD-9-CM
558.3 Allrgic gastro & colitis
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement K52.21 replaces the following previously assigned code(s):

  • K52.2 - Allergic and dietetic gastroenteritis and colitis
FY 2018AddedAdded to the ICD-10-CM code setEffective October 1, 2017.
FY 2019–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About K52.21Overview

Is K52.21 (Allergic and dietetic gastroenteritis and colitis) a billable code?

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

What MS-DRG does K52.21 group to?

When food protein-induced enterocolitis syndrome 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 K52.21?

Under the General Equivalence Mappings, food protein-induced enterocolitis syndrome converts to ICD-9-CM 558.3 (allrgic gastro & colitis). The mapping is approximate, so confirm the match fits the documentation.

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.