ICD-10 Code K35.31 – Acute appendicitis with localized peritonitis and gangrene, without perforation (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K35.31 – Acute appendicitis with localized peritonitis and gangrene, without perforation
What it is
K35.31 identifies acute appendicitis with gangrene and localized peritonitis, but no perforation. Use it when the appendix is necrotic and nearby peritoneal inflammation is documented.
Clinical signs
Typical findings include acute right lower quadrant abdominal pain, localized guarding, and peritoneal irritation around the appendix. Clinical features vary; refer to documentation.
When to use this code
Use this code when the record clearly states gangrenous appendicitis with localized peritonitis and specifically notes no perforation. It also fits operative or pathology documentation confirming gangrene without rupture. If perforation is mentioned or suspected, check documentation.
Do not use for
Do not use K35.31 if the appendix is perforated, if peritonitis is generalized, or if gangrene is not documented. Check documentation for the correct acute appendicitis subtype.
Coding tip
Verify both “gangrene” and “without perforation” in the operative note or final diagnosis before assigning K35.31.