2026 ICD-10-CM Diagnosis Code K04.4Acute apical periodontitis of pulpal origin
ICD-10-CM Codes›K00–K95›K00-K14›K04
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not Chronic
K04.4 is a billable ICD-10-CM diagnosis code for acute apical periodontitis of pulpal origin. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 11 through 13, 157 through 159. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 229 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Any dental condition including traumatic injury; Caries, periodontitis, and other preventable dental conditions; and Disorders of teeth and gingiva.
Code Identity
Code Classification
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Acute apical periodontitis NOS
Type 1 Excludes
- acute periodontitis K05.2
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.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Septic See: condition;
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Gum Disease
If you have gum disease, you're not alone. Many U.S. adults currently have some form of the disease. It ranges from simple gum inflammation, called gingivitis, to serious damage to the tissue and bone supporting the teeth. In the worst cases, you can lose teeth.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert K04.4 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About K04.4Overview
What is the ICD-10 code for acute apical periodontitis of pulpal origin?
The ICD-10-CM code for acute apical periodontitis of pulpal origin is K04.4 (sometimes written as K044). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is K04.4 (Diseases of pulp and periapical tissues) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report acute apical periodontitis of pulpal origin on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does K04.4 group to?
When acute apical periodontitis of pulpal origin is the principal diagnosis on an inpatient stay, it groups to MS-DRG 11, 12, 13, 157, 158, 159, with relative weights from 0.7085 to 5.4541 depending on complications. Higher weights mean higher Medicare reimbursement.
Is K04.4 a CC or MCC?
CMS lists K04.4 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 229 closely related codes in its exclusion list.
What is the ICD-9 equivalent of K04.4?
Under the General Equivalence Mappings, acute apical periodontitis of pulpal origin converts to ICD-9-CM 522.4 (ac apical periodontitis). The mapping is a direct match.
