ICD-10 Code K35.8 – Other and unspecified acute appendicitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K35.8 – Other and unspecified acute appendicitis
What it is
K35.8 identifies acute appendicitis when the record does not specify a more exact type. Use it for an acute appendiceal inflammation that is documented as other or unspecified.
Clinical signs
Typical findings include abdominal pain, often in the right lower quadrant, with tenderness and possible nausea, vomiting, or fever. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents acute appendicitis but does not describe perforation, gangrene, abscess, or a more specific subtype. It also fits cases labeled “other” or “unspecified” acute appendicitis. Check documentation if the note suggests a complication or a different appendiceal diagnosis.
Do not use for
Do not use K35.8 when the record clearly states perforated, gangrenous, or abscessed appendicitis. Also avoid it for chronic appendicitis or non-appendicitis abdominal pain.
Coding tip
Code to the highest documented specificity and verify whether the note names a complication that requires a different K35 code.