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  6. 2024 ICD-10-CM Code K35.21
Version 2024
Replaced Code
Non-Billable Code
New Code

2024 ICD-10-CM Diagnosis Code K35.21

Acute appendicitis with generalized peritonitis, with abscess

ICD-10-CM Code:
K35.21
ICD-10 Code for:
Acute appendicitis with gen peritonitis, with abscess
Is Billable?
Not Valid for Submission
Chronic Condition Indicator: [1]
Not chronic
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Code Classification

  • Diseases of the digestive system
    (K00–K95)
    • Diseases of appendix
      (K35-K38)
      • Acute appendicitis
        (K35)

K35.21 is a non-specific and non-billable diagnosis code code, consider using a code with a higher level of specificity for a diagnosis of acute appendicitis with generalized peritonitis, with abscess. The code is not specific and is NOT valid for the year 2024 for the submission of HIPAA-covered transactions. Category or Header define the heading of a category of codes that may be further subdivided by the use of 4th, 5th, 6th or 7th characters.

Specific Coding Applicable to Acute appendicitis with gen peritonitis, with abscess

Non-specific codes like K35.21 require more digits to indicate the appropriate level of specificity. Consider using any of the following ICD-10-CM codes with a higher level of specificity when coding for acute appendicitis with gen peritonitis, with abscess:

  • Use K35.210 for Acute appendicitis with generalized peritonitis, without perforation, with abscess - BILLABLE CODE

  • Use K35.211 for Acute appendicitis with generalized peritonitis, with perforation and abscess - BILLABLE CODE

  • Use K35.219 for Acute appendicitis with generalized peritonitis, with abscess, unspecified as to perforation - BILLABLE CODE

Clinical Classification

Clinical CategoryCCSR Category CodeInpatient Default CCSROutpatient Default CCSR
Appendicitis and other appendiceal conditionsDIG009Y - Yes, default inpatient assignment for principal diagnosis or first-listed diagnosis.Y - Yes, default outpatient assignment for principal diagnosis or first-listed diagnosis.
Peritonitis and intra-abdominal abscessDIG016N - Not default inpatient assignment for principal diagnosis or first-listed diagnosis.N - Not default outpatient assignment for principal diagnosis or first-listed diagnosis.

New 2024 ICD-10-CM Code

K35.21 is new to ICD-10-CM code set for the FY 2024, effective October 1, 2023. The National Center for Health Statistics (NCHS) has published an update to the ICD-10-CM diagnosis codes which became effective October 1, 2023. This is a new and revised code for the FY 2024 (October 1, 2023 - September 30, 2024).

Replaced Code

This code was replaced in the 2024 ICD-10-CM code set with the code(s) listed below. The National Center for Health Statistics (NCHS) has published an update to the ICD-10-CM diagnosis codes which became effective October 1, 2023. This code was replaced for the FY 2024 (October 1, 2023 - September 30, 2024).


  • K35.210 - Ac appendicitis with gen peritonitis, w/o perf, with abscs
  • K35.211 - Acute appendicitis with gen peritonitis, with perf and abscs
  • K35.219 - Ac appendicitis w gen peritonitis, w abscs, unsp as to perf

Replacement Code

K3521 replaces the following previously assigned ICD-10-CM code(s):

  • K35.2 - Acute appendicitis with generalized peritonitis

Patient Education


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. 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


[Learn More in MedlinePlus]

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.


[Learn More in MedlinePlus]

Code History

  • FY 2024 - Code Added, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019

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.