Updated ICD-10-CM Codes for Appendicitis

November 14th, 2023 - Aimee Wilcox

According to JAMA, there are approximately 250,000 cases of appendicitis diagnosed annually in the United States. Appendicitis can quickly spiral out of control when a perforation of the appendix occurs and a patient becomes septic. Understanding the language used in medical documentation helps with the proper assignment of ICD-10-CM codes and support for testing and treatment. 

The appendix is a finger-shaped pouch that protrudes from the colon, near the cecum, located in the lower right quadrant of the abdomen. Appendicitis is diagnosed when the appendix becomes inflamed, which may be caused by an infection, tumor, or an appendicolith (a buildup of calcified feces within the appendix itself). Appendicitis occurs in men and women, almost equally and most often between the ages of 10 and 30 years old. 

Uncomplicated vs. Complicated Appendicitis

An uncomplicated case usually consists of an inflamed but not ruptured appendix, treatable with antibiotics and if needed, surgery. However, a complicated case of appendicitis can be deadly if not aggressively treated right away, as the appendix ruptures, leaking pus and bacteria into the abdominal cavity resulting in peritonitis, an infection of the peritoneum or the lining of the abdominal cavity and abdominal organs. Peritonitis is either localized (the infection is walled off by organs limiting the spread of the infection to a specific location) or generalized (diffuse) where the infection spreads throughout the entire peritoneal cavity and lining of all the abdominal organs. Left untreated, a complicated case of appendicitis can turn septic and deadly.

Diagnosis and Treatment

After a patient history and examination have been completed, diagnosis may be done through additional testing, such as:

  • Blood tests to check the white blood cell count, which if high, indicates an active infection
  • Imaging studies
    • Ultrasound
    • Abdominal CT scan (preferred)

Treatment depends on the type and severity of the patient's appendicitis. Uncomplicated appendicitis may be treated with an antibiotic and/or surgery to remove the appendix laparoscopically. Complicated cases, especially those with severe infection like sepsis, require intravenous (IV) antibiotics and placement of a surgical drain to get the infection under control and remove the pus from the abdominal cavity. Once the infection is controlled, surgery can be planned to safely remove the ruptured appendix.

Documentation and Code Assignment

Documentation should identify the important details that allow for high-specificity code assignment, such as:

  • acute appendicitis
  • with or without perforation
  • with or without abscess
  • with or without localized or generalized peritonitis
  • with or without gangrene

Acute appendicitis with localized peritonitis is reported with codes from K35.89- with the sixth character identifying the status of perforation, abscess, and gangrene. The new codes, effective as of October 1, 2023 include: 

  • K35.200 without perforation or abscess

  • K35.201 with perforation, without abscess

  • K35.209 without abscess, unspecified as to perforation

  • K35.210 without perforation, with abscess

  • K35.211 with perforation and abscess

  • K35.219 with abscess, unspecified as to perforation



Questions, comments?

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