ICD-10 Code K66.9 – Disorder of peritoneum, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K66.9 – Disorder of peritoneum, unspecified
What it is
K66.9 identifies a documented disorder of the peritoneum when the chart does not name a more specific condition. It is used for nonspecific peritoneal disease, not for a defined infection, injury, or neoplasm.
Clinical signs
Clinical features vary; refer to documentation. Peritoneal disorders may present with abdominal pain, distention, tenderness, ascites, or signs of peritoneal irritation, but the record must support a peritoneal problem.
When to use this code
Use K66.9 when the provider documents a disorder of the peritoneum and no more precise diagnosis is available. It can also fit when the note confirms peritoneal involvement but does not specify the exact disorder. If the record later names a specific condition, code that diagnosis instead.
Do not use for
Do not use this code for peritonitis, adhesions, hemoperitoneum, or other named peritoneal conditions that have their own codes. Check documentation if the cause or exact peritoneal diagnosis is stated.
Coding tip
Query for specificity whenever the provider only says “peritoneal disorder,” because a more exact code may be available.