ICD-10 Code A42.1 – Abdominal actinomycosis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A42.1 – Abdominal actinomycosis
What it is
Abdominal actinomycosis is a chronic bacterial infection caused by Actinomyces species that involves the abdomen or abdominal organs. It often produces a slowly progressive inflammatory mass and may spread across tissue planes.
Clinical signs
Clinical features vary; refer to documentation. Typical findings include abdominal pain, a palpable mass, abscess formation, draining sinus tracts, or findings that mimic malignancy or inflammatory bowel disease.
When to use this code
Use A42.1 when the provider documents abdominal actinomycosis, actinomycotic infection of the abdomen, or a confirmed Actinomyces infection involving abdominal structures. This code fits cases with imaging, surgical, or pathology confirmation. If the record only says “abscess” or “mass,” check documentation before assigning this code.
Do not use for
Do not use this code for actinomycosis limited to other body sites, such as cervicofacial or thoracic infection. Do not assign it for nonspecific abdominal infection without documentation of Actinomyces.
Coding tip
Look for the anatomic site and the organism in the provider note, pathology, or culture report before coding A42.1.