ICD-10-CM 2027
ICD-10 code for fluke infestation
From the official ICD-10-CM alphabetic index entry “Infestation › fluke”. Page updated September 29, 2026.
About coding fluke infestation
The ICD-10-CM code for fluke infestation is B66.9 (Fluke infection, unspecified). The official index lists 11 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on B66.9.
Within B66, choose B66.9 (Fluke infection, unspecified) only when documentation doesn't support a more specific option: Opisthorchiasis (B66.0), Clonorchiasis (B66.1), Dicroceliasis (B66.2), Fascioliasis (B66.3), Paragonimiasis (B66.4), Fasciolopsiasis (B66.5) and other specified fluke infections (B66.8).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC, relative weight 2.1859), DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC, relative weight 1.0235) and DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC, relative weight 0.6787), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific fluke infestation codes (official index)
- blood NOS
- cat liver B66.0 — Opisthorchiasis
- intestinal B66.5 — Fasciolopsiasis
- liver (sheep) B66.3 — Fascioliasis
- cat B66.0 — Opisthorchiasis
- Chinese B66.1 — Clonorchiasis
- due to clonorchiasis B66.1 — Clonorchiasis
- oriental B66.1 — Clonorchiasis
- lancet B66.2 — Dicroceliasis
- lung (oriental) B66.4 — Paragonimiasis
- sheep liver B66.3 — Fascioliasis
- specified type NEC B66.8 — Other specified fluke infections
Common questions about fluke infestation ICD-10 codes
What is the ICD-10 code for fluke infestation?
- B66.9 — Fluke infection, unspecified. More specific codes apply when the documentation supports them: B66.0, B66.5, B66.3, B66.0 and others below.
What is the ICD-10 code for cat liver fluke infestation?
- B66.0 — Opisthorchiasis.
What is the ICD-10 code for intestinal fluke infestation?
- B66.5 — Fasciolopsiasis.
What is the ICD-10 code for liver fluke infestation?
- B66.3 — Fascioliasis.
What is the ICD-10 code for lancet fluke infestation?
- B66.2 — Dicroceliasis.
What is the ICD-10 code for lung fluke infestation?
- B66.4 — Paragonimiasis.
What is the ICD-10 code for sheep liver fluke infestation?
- B66.3 — Fascioliasis.
Is B66.9 billable?
- Yes. B66.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can B66.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict B66.9 as a principal diagnosis.
Is B66.9 a CC or MCC?
- No. B66.9 is neither a CC nor an MCC under MS-DRG v44.0.