2026 ICD-10-CM Diagnosis Code K37Unspecified appendicitis
ICD-10-CM Codes›K00–K95›K35-K38›K37
- Billable — Valid for Submission
- Not Chronic
K37 is a billable ICD-10-CM diagnosis code for unspecified appendicitis. 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. Coders also document this condition as appendicitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Appendicitis and other appendiceal conditions.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Appendicitis
- Crohn disease of appendix
- Focal appendicitis
- Neutropenic typhlitis
- Periappendicitis
- Retrocecal appendicitis
- Retroileal appendicitis
- Typhlitis
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Type 1 Excludes
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.
- Perityphlitis - See Also: Cecitis; - K37
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- Appendicitis(pneumococcal) (retrocecal)
- Perityphlitis
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Appendicitis
acute inflammation of the appendix. acute appendicitis is classified as simple, gangrenous, or perforated.Typhlitis
necrotizing inflammation of the cecum (typhlon in greek), sometimes spreading to the appendix and/or the ileum. symptoms include abdominal pain and diarrhea. its pathogenesis is multifactorial. typhlitis is often associated with neutropenia and chemotherapy in immunocompromised individuals (immunocompromised host).Appendix
a worm-like blind tube extension from the cecum.
Patient EducationClinical
Appendicitis
The appendix is a small, tube-like organ attached to the first part of the large intestine. It is located in the lower right part of the abdomen. It has no known function. A blockage inside of the appendix causes appendicitis. The blockage leads to increased pressure, problems with blood flow, and inflammation.
Read the full article at MedlinePlus
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Convert K37 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About K37Overview
Is K37 (Unspecified appendicitis) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report unspecified appendicitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does K37 group to?
When unspecified appendicitis 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 K37?
Under the General Equivalence Mappings, unspecified appendicitis converts to ICD-9-CM 541 (appendicitis NOS). The mapping is a direct match.
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.
