B66.1
Clonorchiasis
B66.1 (also written B661) is a billable ICD-10-CM diagnosis code for clonorchiasis. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 8 codes in category B66 (Other fluke infections). The Alphabetic Index lists it under 14 entries. Its coding notes include a Use additional code instruction and 5 Excludes2 entries.
Use additional code
Add the listed code as a secondary code, if known.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (5 notes)
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Home Health Primary
Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Infectious Disease, Neoplasms, and Blood-Forming Diseases clinical group.
Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 8 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CIncludes
Further defines or gives examples of the content of the category.
Also from chapter/block level (1 note)
- diseases generally recognized as communicable or transmissible
Inclusion terms
Conditions classified to this code.
- Chinese liver fluke disease
- Infection due to Clonorchis sinensis
- Oriental liver fluke disease
Alphabetic Index terms
Terms the official Alphabetic Index lists for this code. 14 entries
- Cholangiohepatitis, due to fluke infestation
- Cirrhosis, cirrhotic (hepatic) (liver), biliary (cholangiolitic) (cholangitic) (hypertrophic) (obstructive) (pericholangiolitic), due to, Clonorchiasis
- Clonorchiasis, clonorchis infection (liver)
- Disease, diseased, Chinese liver fluke
- Disease, diseased, liver (chronic) (organic), fluke, Chinese
- Disease, diseased, liver (chronic) (organic), fluke, oriental
- Disease, diseased, Oriental liver fluke
- Distomiasis, hepatic, due to Clonorchis sinensis
- Distomiasis, liver, due to Clonorchis sinensis
- Infection, infected, infective (opportunistic), Clonorchis (sinensis) (liver)
- Infestation, Clonorchis (sinensis) (liver)
- Infestation, fluke, liver (sheep), Chinese