2027 ICD-10-CM Diagnosis Code K37Unspecified appendicitis

ICD-10-CM Codes›K00–K95›K35-K38›K37

ICD-10-CM K37
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

K37 is a billable ICD-10-CM diagnosis code for unspecified appendicitis. 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. 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

ICD-10-CM Code
K37
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified appendicitis
Short Description
Unspecified appendicitis
Same as the full description in the CMS dataset.
Chapter
K35-K38
Diseases of appendix

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK35-K38Diseases of appendix
CategoryK37Unspecified appendicitis
This CodeK37Unspecified appendicitis

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

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to K37: its own notes plus those printed at Chapter 11. A note printed at a category, block or chapter applies to every code under it.

Excludes1

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

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 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 DIG009
Appendicitis and other appendiceal conditions
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Appendicitis

    acute inflammation of the appendix. acute appendicitis is classified as simple, gangrenous, or perforated.

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

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

Convert K37 to ICD-9-CMHistory

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

ICD-9-CM
541 Appendicitis NOS
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About K37Overview

What is the ICD-10 code for unspecified appendicitis?

The ICD-10-CM code for unspecified appendicitis is K37. It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

What MS-DRG does K37 group to?

When unspecified appendicitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 394, 395, 393, with relative weights from 0.6379 to 1.5877 depending on complications. Higher weights mean higher Medicare reimbursement.

Can K37 be reported with a code from K35.2?

Not as a rule. The Excludes1 note on K37 lists "unspecified appendicitis with peritonitis (K35.2-, K35.3-)". 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).

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.