ICD-10 Code K35.2 – Acute appendicitis with generalized peritonitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K35.2 – Acute appendicitis with generalized peritonitis
What it is
K35.2 identifies acute appendicitis complicated by generalized peritonitis, meaning the appendix is inflamed and infection or irritation has spread throughout the abdominal cavity. Use it when the documentation clearly states generalized peritonitis.
Clinical signs
Typical findings include acute abdominal pain, guarding, rebound tenderness, and diffuse peritoneal irritation. Clinical features vary; refer to documentation for confirmation of generalized peritonitis.
When to use this code
Use K35.2 when the provider documents acute appendicitis with generalized peritonitis, diffuse peritonitis, or peritoneal spread involving the whole abdomen. You should code it when the record supports an acute appendiceal process with generalized abdominal contamination, not a localized abscess alone.
Do not use for
Do not use this code for uncomplicated appendicitis or appendicitis with localized peritonitis only. If the note is unclear about the extent of peritonitis, check documentation.
Coding tip
Confirm the wording “generalized peritonitis” in the provider note before assigning K35.2.