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B66.0 ICD-10-CM Code: Opisthorchiasis

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
2 inclusion terms

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 441 — DISORDERS OF LIVER EXCEPT MALIGNANCY, CIRRHOSIS OR ALCOHOLIC HEPATITIS WITH MCC (MDC 07)
  • MS-DRG 442 — DISORDERS OF LIVER EXCEPT MALIGNANCY, CIRRHOSIS OR ALCOHOLIC HEPATITIS WITH CC (MDC 07)
  • MS-DRG 443 — DISORDERS OF LIVER EXCEPT MALIGNANCY, CIRRHOSIS OR ALCOHOLIC HEPATITIS WITHOUT CC/MCC (MDC 07)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for B66.0 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Infection due to cat liver fluke
  • Infection due to Opisthorchis (felineus)(viverrini)

Code Overview

Opisthorchiasis is a billable ICD-10-CM diagnosis code (B66.0).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (7)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Verify Before Coding

  • CC as a secondary diagnosis (FY2026). Can raise the stay's MS-DRG severity tier.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name B66.0 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes2 note: J82 — Pulmonary eosinophilia, not elsewhere classified (via B66.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Referenced by 2 Code First instructions across 2 chapters: H94.0 — Acoustic neuritis in infectious and parasitic diseases classified elsewhere (via B66.-), K67 — Disorders of peritoneum in infectious diseases classified elsewhere (via B66.-).

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: CC — Complication or Comorbidity. Reported as a secondary diagnosis, this code raises the stay's MS-DRG severity tier — except when the principal diagnosis is one of 8 clinically related codes on its CMS exclusion list.

Named in the grouper logic of 3 MS-DRGs: DRG 441 (MDC 07), DRG 442 (MDC 07), DRG 443 (MDC 07).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):INF009 — Parasitic, other specified and unspecified infections (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical process (MS-DRG)

Acts as CC — raises the severity of other admissions. CMS groups these diagnoses into one MS-DRG principal-diagnosis exclusion process — a CC/MCC on this list never raises severity when the principal diagnosis is also on it.

B66.1 — Clonorchiasis, B66.2 — Dicroceliasis, B66.3 — Fascioliasis, B66.4 — Paragonimiasis, B66.5 — Fasciolopsiasis, B66.8 — Other specified fluke infections, B66.9 — Fluke infection, unspecified

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Parasitic, other specified and unspecified infections).

B60.19 — Other acanthamebic disease, B60.2 — Naegleriasis, B60.8 — Other specified protozoal diseases, B64 — Unspecified protozoal disease, B65.0 — Schistosomiasis due to Schistosoma haematobium [urinary schistosomiasis], B65.1 — Schistosomiasis due to Schistosoma mansoni [intestinal schistosomiasis], B65.2 — Schistosomiasis due to Schistosoma japonicum, B65.3 — Cercarial dermatitis, B65.8 — Other schistosomiasis, B65.9 — Schistosomiasis, unspecified, B66.1 — Clonorchiasis, B66.2 — Dicroceliasis, B66.3 — Fascioliasis, B66.4 — Paragonimiasis, B66.5 — Fasciolopsiasis, B66.8 — Other specified fluke infections, B66.9 — Fluke infection, unspecified, B67.0 — Echinococcus granulosus infection of liver, B67.1 — Echinococcus granulosus infection of lung, B67.2 — Echinococcus granulosus infection of bone, +235 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Infestation”; these codes share that main term but sit in a different category of the Tabular List.

B37.0 — Candidal stomatitis (mouth), B55.1 — Cutaneous leishmaniasis (eyelid, in, leishmaniasis), B60.8 — Other specified protozoal diseases (protozoal NEC, specified NEC), B64 — Unspecified protozoal disease (protozoal NEC), B65.0 — Schistosomiasis due to Schistosoma haematobium [urinary schistosomiasis] (Schistosoma, haematobium), B65.1 — Schistosomiasis due to Schistosoma mansoni [intestinal schistosomiasis] (Schistosoma, mansoni), B65.2 — Schistosomiasis due to Schistosoma japonicum (Schistosoma, japonicum), B65.3 — Cercarial dermatitis (Schistosoma, cercariae), B65.8 — Other schistosomiasis (Schistosoma, bovis), B65.9 — Schistosomiasis, unspecified (Schistosoma), B67.4 — Echinococcus granulosus infection, unspecified (dog tapeworm), B68.0 — Taenia solium taeniasis (pork tapeworm), B68.1 — Taenia saginata taeniasis (beef tapeworm), B68.9 — Taeniasis, unspecified (Taenia), B70.0 — Diphyllobothriasis (fish tapeworm), B70.1 — Sparganosis (Sparganum), B71.0 — Hymenolepiasis (Hymenolepis), B71.1 — Dipylidiasis (cestodes, dipylidiasis), B71.8 — Other specified cestode infections (Diplogonoporus), B71.9 — Cestode infection, unspecified (tapeworm), +53 more

Contextual Map

Every relationship of B66.0 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run B66.0 with these 3 related codes in Claim Check

Hierarchy

Referenced by Excludes2 notes

Referenced by Code First instructions

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 07 — Diseases and Disorders of the Hepatobiliary System and Pancreas[MDC crossing]: “Diseases and Disorders of the Hepatobiliary System and Pancreas — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 2,481 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

  • Infection, infected, infective (opportunistic), cat liver fluke[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infection, infected, infective (opportunistic), Opisthorchis (felineus) (viverrini)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infestation, cat liver fluke[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infestation, fluke, cat liver[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infestation, fluke, liver (sheep), cat[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Infestation, Opisthorchis (felineus) (viverrini)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Opisthorchiasis (felineus) (viverrini)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "B66.0 — Opisthorchiasis." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/b66.0-opisthorchiasis

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Opisthorchiasis

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to B66.0 in its code family, with their registry titles.

View all codes in the B66 family