ICD-10 Code A18.31 – Tuberculous peritonitis (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A18.31 – Tuberculous peritonitis
What it is
Tuberculous peritonitis is tuberculosis infection involving the peritoneum, the lining of the abdominal cavity. Use this code when documentation identifies peritoneal TB, whether primary or part of disseminated disease.
Clinical signs
Common findings include abdominal pain, distension, ascites, fever, weight loss, and malaise. Clinical features vary; refer to documentation, since diagnosis may rely on imaging, fluid studies, biopsy, or other evidence of tuberculosis.
When to use this code
Use A18.31 when the provider documents tuberculous peritonitis or peritoneal tuberculosis as the diagnosis. It also fits when the record shows TB infection of the peritoneum with abdominal involvement, even if pulmonary disease is not the main focus.
Code it from clear clinical documentation, pathology, or imaging-supported assessment. If the record only says “peritonitis” without tuberculosis, do not assume this code; check documentation.
Do not use for
Do not use this code for nonspecific infectious peritonitis, spontaneous bacterial peritonitis, or peritonitis from other causes. If tuberculosis is not documented, or the site is not the peritoneum, choose a different code.
Coding tip
Confirm that the chart explicitly links the peritonitis to tuberculosis before assigning A18.31.