ICD-10 Code K65 – Peritonitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K65 – Peritonitis
What it is
K65 identifies inflammation of the peritoneum, the membrane lining the abdominal cavity and covering abdominal organs. Use it when documentation states peritonitis without a more specific cause or site.
Clinical signs
Typical findings include abdominal pain, tenderness, guarding, and signs of peritoneal irritation. Clinical features vary; refer to documentation for the documented cause, extent, and acuity.
When to use this code
Use K65 when the provider documents peritonitis and does not give a more specific code. It may apply to infectious, chemical, or other nonspecific peritoneal inflammation when the record supports that diagnosis. If the cause or related condition is documented, code that condition as instructed.
Do not use for
Do not use K65 for generalized abdominal pain, ascites, or postoperative abdominal discomfort without documented peritonitis. Check documentation if the record instead describes another intra-abdominal infection or a complication code.
Coding tip
Assign the most specific peritonitis code available and verify any documented cause, such as perforation, infection, or dialysis-related disease.