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ICD-10-CM 2027 diagnosis code

K04.4Acute apical periodontitis of pulpal origin

✓ Billable / specificCC — complication/comorbidity

K04.4 is a valid, billable ICD-10-CM code for acute apical periodontitis of pulpal origin. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About K04.4

K04.4 is the ICD-10-CM diagnosis code for acute apical periodontitis of pulpal origin. It belongs to category K04 (diseases of pulp and periapical tissues), block K00-K14 (diseases of oral cavity and salivary glands) and chapter 11 (diseases of the digestive system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within K04 (diseases of pulp and periapical tissues), K04.4 is specifically for acute apical periodontitis of pulpal origin. Related codes cover pulpitis (K04.0), necrosis of pulp (K04.1), pulp degeneration (K04.2), abnormal hard tissue formation in pulp (K04.3), chronic apical periodontitis (K04.5), periapical abscess with sinus (K04.6), periapical abscess without sinus (K04.7), Radicular cyst (K04.8) and 1 more.

Don't report K04.4 together with the conditions in its Excludes1 note: acute periodontitis (K05.2-).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 011 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy with MCC, relative weight 5.6154), DRG 012 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy with CC, relative weight 4.381), DRG 013 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy without CC/MCC, relative weight 2.7307), DRG 157 (Dental and Oral Diseases with MCC, relative weight 1.809), DRG 158 (Dental and Oral Diseases with CC, relative weight 0.9366) and DRG 159 (Dental and Oral Diseases without CC/MCC, relative weight 0.6893), in Pre-MDC and MDC 03 (Diseases and Disorders of the Ear, Nose, Mouth and Throat), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 522.4 (acute apical periodontitis of pulpal origin).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Acute apical periodontitis NOS
Excludes1Not coded here — never report together with this code

Notes that apply from higher levels

Instructions written at a parent level also apply to K04.4.

Broader instructions also apply from Chapter 11: Diseases of the digestive system.

Alphabetic index entries

2 entries

Terms in the official ICD-10-CM index that lead to K04.4.

Codes whose notes reference K04.4

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

ICD-9-CM equivalent

Converter →
  • 522.4Acute apical periodontitis of pulpal originexact

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about K04.4

Is K04.4 billable?

Yes. K04.4 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can K04.4 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict K04.4 as a principal diagnosis.

Is K04.4 a CC or MCC?

K04.4 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.

What DRG does K04.4 group to?

K04.4 is used in the MS-DRG v44.0 logic for MS-DRG 011 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy with MCC), MS-DRG 012 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy with CC), MS-DRG 013 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy without CC/MCC), MS-DRG 157 (Dental and Oral Diseases with MCC), MS-DRG 158 (Dental and Oral Diseases with CC) and MS-DRG 159 (Dental and Oral Diseases without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for K04.4?

The CMS General Equivalence Mappings map K04.4 to ICD-9-CM 522.4.