ICD-10 Code K35.20 – Acute appendicitis with generalized peritonitis, without abscess (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K35.20 – Acute appendicitis with generalized peritonitis, without abscess
What it is
K35.20 identifies acute inflammation of the appendix complicated by generalized peritonitis, but without a documented abscess. Use it when the appendicitis has spread infection or inflammation throughout the peritoneal cavity.
Clinical signs
Typical findings include acute abdominal pain with peritoneal irritation, guarding, rebound tenderness, and diffuse abdominal tenderness. Clinical features vary; refer to documentation for evidence of generalized peritonitis and absence of abscess.
When to use this code
Use this code when the record clearly states acute appendicitis with generalized peritonitis and does not mention an abscess. It also fits operative, imaging, or discharge documentation that confirms diffuse peritoneal involvement. If the note is unclear, check documentation before assigning the code.
Do not use for
Do not use K35.20 if an appendiceal abscess is documented, or if the peritonitis is localized rather than generalized. Do not assume this code from appendicitis alone.
Coding tip
Confirm both elements in the chart: generalized peritonitis and no abscess; if either is missing, verify the documentation.