ICD-10-CM Code for Intestinal Methanogen Overgrowth
There is no specific ICD-10-CM code for intestinal methanogen overgrowth (IMO); use K63.89 (Other specified diseases of intestine) or K90.89 (Other intestinal malabsorption) depending on the clinical presentation.
Understanding the Coding Challenge
Intestinal methanogen overgrowth is a recently recognized distinct entity from small intestinal bacterial overgrowth (SIBO), characterized by overgrowth of methane-producing archaea, specifically Methanobrevibacter smithii 1, 2. The term "IMO" was proposed because these organisms are archaea (not bacteria) and can overgrow outside the small intestine 1.
Recommended Coding Approach
Primary Code Options:
K63.89 (Other specified diseases of intestine) - Use this code when IMO presents primarily with gastrointestinal symptoms such as abdominal pain, distension, and bloating without significant malabsorption 3
K90.89 (Other intestinal malabsorption) - Use this code when IMO presents with malabsorption features including deficiency of fat-soluble vitamins, vitamin B12, or iron deficiency anemia 3, 2
Clinical Context for Code Selection:
If the patient has documented malnutrition, vitamin deficiencies (B12, fat-soluble vitamins), or iron deficiency anemia, K90.89 is more appropriate 3, 2
If the patient presents primarily with functional symptoms (constipation, bloating, abdominal pain) without malabsorption, K63.89 is more appropriate 3, 1
Important Coding Considerations
Documentation Requirements:
Document the diagnostic method used (breath testing showing elevated methane levels ≥10 ppm is diagnostic for IMO) 4, 5
Note associated symptoms: IMO typically presents with constipation rather than diarrhea, distinguishing it from hydrogen-producing SIBO 3, 1
Record any nutritional deficiencies or malabsorption findings to support code selection 3, 2
Common Pitfall:
Do not use K90.4 (Malabsorption due to intolerance) - This code is reserved for specific intolerances (lactose, fructose, etc.) and does not accurately represent IMO 3
Avoid using unspecified codes when clinical documentation supports a more specific diagnosis - always choose between K63.89 or K90.89 based on the clinical presentation 3