K04.4
Acute apical periodontitis of pulpal origin
K04.4 (also written K044) is a billable ICD-10-CM diagnosis code for acute apical periodontitis of pulpal origin. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 12 codes in category K04 (Diseases of pulp and periapical tissues). The Alphabetic Index lists it under 2 entries. Its coding notes include 1 Excludes1 entry and 8 Excludes2 entries.
Excludes1
Not coded here. The listed conditions generally should not be reported together.
- acute periodontitis (K05.2-)
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (8 notes)
- 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)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 229 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CInclusion terms
Conditions classified to this code.
- Acute apical periodontitis NOS
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 2 entries