K35.80 Unspecified acute appendicitis

✓ Billable ICD-10-CM 2026
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The ICD-10-CM code for Unspecified acute appendicitis is K35.80 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Section
K35-K38: Diseases of appendix (K35-K38)
Category K35
20 codes (13 billable)
FY2026 Status
Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to K35.80:

  • Appendicitis (pneumococcal) (retrocecal) › acute (catarrhal) (fulminating) (obstructive) (retrocecal) (suppurative)
  • Gangrene, gangrenous (connective tissue) (dropsical) (dry) (moist) (skin) (ulcer) › appendix

Inclusion Terms

  • Acute appendicitis NOS
  • Acute appendicitis without (localized) (generalized) peritonitis

U.S. Hospital Utilization

  • An estimated 51,140 U.S. inpatient stays in 2023 included K35.80 among the documented diagnoses.
  • 41,575 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Chapter 11 reserved for future expansion

11. Chapter 11: Diseases of the Digestive System (K00-K95) Reserved for future guideline expansion

— ICD-10-CM Official Guidelines for Coding and Reporting, FY2026, Section I.C.11

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

Related Codes

Parent Code

K35 Acute appendicitis

Related Codes in K35

K35 Acute appendicitis K35.2 Acute appendicitis with generalized peritonitis K35.20 Acute appendicitis with generalized peritonitis, without abscess K35.200 Acute appendicitis with generalized peritonitis, without perforation or abscess K35.201 Acute appendicitis with generalized peritonitis, with perforation, without abscess K35.209 Acute appendicitis with generalized peritonitis, without abscess, unspecified as to perforation K35.21 Acute appendicitis with generalized peritonitis, with abscess K35.210 Acute appendicitis with generalized peritonitis, without perforation, with abscess K35.211 Acute appendicitis with generalized peritonitis, with perforation and abscess K35.219 Acute appendicitis with generalized peritonitis, with abscess, unspecified as to perforation K35.3 Acute appendicitis with localized peritonitis K35.30 Acute appendicitis with localized peritonitis, without perforation or gangrene K35.31 Acute appendicitis with localized peritonitis and gangrene, without perforation K35.32 Acute appendicitis with perforation, localized peritonitis, and gangrene, without abscess K35.33 Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess K35.8 Other and unspecified acute appendicitis K35.89 Other acute appendicitis K35.890 Other acute appendicitis without perforation or gangrene K35.891 Other acute appendicitis without perforation, with gangrene
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Reviewed by Prajwal Shrestha, CPC, CRC
Certified Professional Coder (CPC) and Certified Risk Adjustment Coder (CRC) · AAPC Member ID 01997614 · About · Editorial policy · Content last reviewed: 2025-10-01

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