K35.33 Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess

The ICD-10-CM code for Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess is K35.33 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

11: Diseases of the digestive system (K00-K95)

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 K35.33:

• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) › subcecal
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) › perityphlic
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) › pericecal
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) › periappendicular
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) › cecum
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) › appendix
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) › postcecal
• Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) › ileocecal

Inclusion Terms

• (Acute) appendicitis with (peritoneal) abscess NOS
• Ruptured appendix with localized peritonitis and abscess

U.S. Hospital Utilization

• An estimated 42,575 U.S. inpatient stays in 2023 included K35.33 among the documented diagnoses.
• 31,630 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

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

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)