ICD-10 Code A09 – Infectious gastroenteritis and colitis, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A09 – Infectious gastroenteritis and colitis, unspecified
What it is
A09 is used for infectious inflammation of the stomach and intestines when the specific organism is not identified. It covers acute diarrhea or colitis attributed to infection, but the cause remains unspecified in the record.
Clinical signs
Typical findings include diarrhea, abdominal cramping, nausea, vomiting, and sometimes fever. Clinical features vary; refer to documentation when the note does not clearly identify the infectious cause.
When to use this code
Use A09 when the provider documents infectious gastroenteritis, infectious colitis, or gastroenteritis/colitis due to infection without naming the organism. It also fits cases where the chart supports an infectious process, but the specific pathogen is not recorded. You should code the documented diagnosis, not a suspected cause.
Do not use for
Do not use A09 for noninfectious diarrhea, irritable bowel syndrome, or inflammatory bowel disease. If the organism is identified, check documentation for a more specific code.
Coding tip
Assign A09 only when the record supports infection and no more specific infectious code is documented.