ICD-10 Code K58.9 – Irritable bowel syndrome, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K58.9 – Irritable bowel syndrome, unspecified
What it is
K58.9 identifies irritable bowel syndrome when the provider documents IBS but does not specify constipation, diarrhea, or mixed bowel habits. It is a functional bowel disorder, so symptoms occur without a clearly defined structural cause.
Clinical signs
Typical findings include recurrent abdominal pain with bloating and altered bowel habits. Clinical features vary; refer to documentation, especially when the record does not clearly state the predominant stool pattern.
When to use this code
Use K58.9 when the chart supports IBS, but the subtype is not documented or cannot be determined from the note. It is appropriate for encounters focused on chronic, recurring IBS symptoms without a more specific classification. If the provider later specifies constipation, diarrhea, or mixed pattern, code to that documented subtype instead.
Do not use for
Do not use K58.9 if the documentation clearly identifies IBS with constipation, diarrhea, or mixed symptoms. Also avoid it when another gastrointestinal disorder better explains the symptoms; check documentation.
Coding tip
Before assigning K58.9, look for subtype wording in the assessment, problem list, or past history.