2027 ICD-10-CM Diagnosis Code K55.30Necrotizing enterocolitis, unspecified

ICD-10-CM Codes›K00–K95›K55-K64›K55

ICD-10-CM K55.30
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

K55.30 is a billable ICD-10-CM diagnosis code for necrotizing enterocolitis, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 393 through 395, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 23 closely related codes. Coders also document this condition as adult necrotizing enterocolitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified gastrointestinal disorders.

K55.30 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 107 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 107, ESRD (V21) category 107, and ESRD (V24) category 107 for payment year 2027.

Code Identity

ICD-10-CM Code
K55.30
Billable Status
Yes — Valid for Submission
Code Describes
Necrotizing enterocolitis, unspecified
Short Description
Necrotizing enterocolitis, unspecified
Same as the full description in the CMS dataset.
Parent Code
K55.3
Necrotizing enterocolitis

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK55-K64Other diseases of intestines
CategoryK55Vascular disorders of intestine
This CodeK55.30Necrotizing enterocolitis, unspecified

Medicare Risk Adjustment (HCC)Billing

K55.30 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
Dropped in V28 see all codes that no longer risk-adjust
Prior Model (CMS-HCC V24)
HCC 107
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
Other CMS Models
PACE (CMS-HCC V22): HCC 107 · ESRD (V21): HCC 107 · ESRD (V24): HCC 107
ESRD V21 weights: 0.126 dialysis, 0.300–0.431 functioning graft · ESRD V24 weights: 0.144 dialysis, 0.324–0.586 functioning graft
Part D (RxHCC)
Not mapped
K55.30 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2027 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.

  • Adult necrotizing enterocolitis
  • Inflammation of small intestine caused by ionizing radiation

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to K55.30: its own notes plus those printed at K55.3, K55, and Chapter 11. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Necrotizing enterocolitis, NOS

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From K55.3 Necrotizing enterocolitis applies to 4 codes
  • necrotizing enterocolitis of newborn (P77.-)
From K55 Vascular disorders of intestine applies to 27 codes
  • necrotizing enterocolitis of newborn (P77.-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From K55.3 Necrotizing enterocolitis applies to 4 codes
  • necrotizing enterocolitis due to Clostridium difficile (A04.7-)
From K55 Vascular disorders of intestine applies to 27 codes
  • angioectasia (angiodysplasia) duodenum (K31.81-)
From Chapter 11 (K00-K95) Diseases of the digestive system applies to 863 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

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 DIG025
Other specified and unspecified gastrointestinal disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Enterocolitis, Necrotizing

    enterocolitis with extensive ulceration (ulcer) and necrosis. it is observed primarily in low birth weight infant.

Patient EducationClinical

Digestive Diseases

When you eat, your body breaks food down to a form it can use to build and nourish cells and provide energy. This process is called digestion.

Read the full article at MedlinePlus

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

Convert K55.30 to ICD-9-CMHistory

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

ICD-9-CM
557.0 Ac vasc insuff intestine
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement K55.30 replaces the following previously assigned code(s):

  • K55.8 - Other vascular disorders of intestine
FY 2019AddedAdded to the ICD-10-CM code setEffective October 1, 2018.
FY 2020–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About K55.30Overview

What is the ICD-10 code for necrotizing enterocolitis, unspecified?

The ICD-10-CM code for necrotizing enterocolitis, unspecified is K55.30 (sometimes written as K5530). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is K55.30 (Necrotizing enterocolitis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report necrotizing enterocolitis, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does K55.30 group to?

When necrotizing enterocolitis, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 394, 395, 393, with relative weights from 0.6379 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.

Is K55.30 a CC or MCC?

CMS lists K55.30 as an MCC (major complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 23 closely related codes in its exclusion list.

Can K55.30 be reported with a code from P77?

Not as a rule. The Excludes1 note at K55.3, which applies to K55.30, lists "necrotizing enterocolitis of newborn (P77.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

Does K55.30 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. K55.30 mapped to HCC 107 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 107 (Vascular Disease with Complications), ESRD (V21) category 107 (Vascular Disease with Complications), and ESRD (V24) category 107 (Vascular Disease with Complications).