ICD-10-CM Code K35.33

Acute appendicitis with perforation and localized peritonitis, with abscess

Version 2020 Billable Code

Valid for Submission

K35.33 is a billable code used to specify a medical diagnosis of acute appendicitis with perforation and localized peritonitis, with abscess. The code is valid for the year 2020 for the submission of HIPAA-covered transactions. The ICD-10-CM code K35.33 might also be used to specify conditions or terms like abscess of appendix, acute appendicitis with peritoneal abscess, acute fulminating appendicitis, acute fulminating appendicitis with perforation and peritonitis, acute gangrenous appendicitis, acute gangrenous appendicitis with perforation and peritonitis, etc

Short Description:Acute appendicitis with perf and loc peritonitis, with abscs
Long Description:Acute appendicitis with perforation and localized peritonitis, with abscess

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with guidance for inclusions, exclusions, descriptions and more. The following references are applicable to the code K35.33:

Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • (Acute) appendicitis with (peritoneal) abscess NOS
  • Ruptured appendix with localized peritonitis and abscess

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code K35.33 are found in the index:


The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Abscess of appendix
  • Acute appendicitis with peritoneal abscess
  • Acute fulminating appendicitis
  • Acute fulminating appendicitis with perforation AND peritonitis
  • Acute gangrenous appendicitis
  • Acute gangrenous appendicitis with perforation AND peritonitis
  • Acute perforated appendicitis
  • Necrotic enteritis
  • Pericecal abscess
  • Rupture of appendix
  • Rupture of appendix

Diagnostic Related Groups

The ICD-10 code K35.33 is grouped in the following groups for version MS-DRG V37.0 What are Diagnostic Related Groups?
The Diagnostic Related Groups (DRGs) are a patient classification scheme which provides a means of relating the type of patients a hospital treats. The DRGs divides all possible principal diagnoses into mutually exclusive principal diagnosis areas referred to as Major Diagnostic Categories (MDC).
applicable from 10/01/2019 through 09/30/2020.


Replacement Code

K3533 replaces the following previously assigned ICD-10 code(s):

  • K35.3 - Acute appendicitis with localized peritonitis

Code Classification

  • Diseases of the digestive system (K00–K93)
    • Diseases of appendix (K35-K38)
      • Acute appendicitis (K35)

Code History

  • FY 2019 - Code Added, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020

Information for Patients


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. If the blockage is not treated, the appendix can burst and spread infection into the abdomen. This causes a condition called peritonitis.

The main symptom is pain in the abdomen, often on the right side. It is usually sudden and gets worse over time. Other symptoms may include

  • Swelling in the abdomen
  • Loss of appetite
  • Nausea and vomiting
  • Constipation or diarrhea
  • Inability to pass gas
  • Low fever

Not everyone with appendicitis has all these symptoms.

Appendicitis is a medical emergency. Treatment almost always involves removing the appendix. Anyone can get appendicitis, but it is more common among people 10 to 30 years old.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

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Peritoneal Disorders

Your peritoneum is the tissue that lines your abdominal wall and covers most of the organs in your abdomen. A liquid, peritoneal fluid, lubricates the surface of this tissue.

Disorders of the peritoneum are not common. They include

  • Peritonitis - an inflammation of the peritoneum
  • Cancer
  • Complications from peritoneal dialysis

Your doctor may use imaging tests or lab tests to analyze the peritoneal fluid to diagnose the problem. Treatment of peritoneal disorders depends on the cause.

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