2026 ICD-10-CM Diagnosis Code K55.33Stage 3 necrotizing enterocolitis
ICD-10-CM Codes›K00–K95›K55-K64›K55
- Billable — Valid for Submission
- Not Chronic
K55.33 is a billable ICD-10-CM diagnosis code for stage 3 necrotizing enterocolitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 393 through 395. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified gastrointestinal disorders.
Code Identity
Code Classification
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Necrotizing enterocolitis with perforation
- Necrotizing enterocolitis with pneumatosis and perforation
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
- Enterocolitis - See Also: Enteritis; - K52.9
- necrotizing - K55.30
- with
- perforation - K55.33
- pneumatosis - K55.32
- and perforation - K55.33
- in non-newborn - K55.30
- stage 3 (with pneumatosis, with perforation) - K55.33
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- Enterocolitis
- necrotizing
- with
- perforation
- Enterocolitis
- necrotizing
- with
- pneumatosis
- and perforation
- Enterocolitis
- necrotizing
- in non-newborn
- stage 3 (with pneumatosis, with perforation)
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Convert K55.33 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code History & ChangesHistory
Replacement K55.33 replaces the following previously assigned code(s):
- K55.8 - Other vascular disorders of intestine
Questions About K55.33Overview
Is K55.33 (Necrotizing enterocolitis) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report stage 3 necrotizing enterocolitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does K55.33 group to?
When stage 3 necrotizing enterocolitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 393, 394, 395, with relative weights from 0.6490 to 1.5993 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of K55.33?
Under the General Equivalence Mappings, stage 3 necrotizing enterocolitis converts to ICD-9-CM 557.0 (ac vasc insuff intestine). 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.
