2027 ICD-10-CM Diagnosis Code B66.1Clonorchiasis
ICD-10-CM Codes›A00–B99›B65-B83›B66
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Not Chronic
B66.1 is a billable ICD-10-CM diagnosis code for clonorchiasis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 441 through 443. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 8 closely related codes. Coders also document this condition as acute clonorchiasis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Parasitic, other specified and unspecified infections.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acute clonorchiasis
- Biliary cirrhosis
- Chronic clonorchiasis
- Clonorchiasis
- Clonorchiasis with biliary cirrhosis
- Fibrosis of bile duct
- Infection of bile duct caused by parasite
- Infectious cirrhosis
- Opisthorchiasis
- Parasitic cirrhosis
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to B66.1: its own notes plus those printed at Chapter 1. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- diseases generally recognized as communicable or transmissible
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Chinese liver fluke disease
- Infection due to Clonorchis sinensis
- Oriental liver fluke disease
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- 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)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify resistance to antimicrobial drugs (Z16.-)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name B66.1, its category, or a range that includes it.
Code First 1
These codes say to code first a condition named in the note, and B66.1 is one of the conditions named.
- K67 Disorders of peritoneum in infectious diseases classified elsewhere
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
Chinese liver fluke B66.1
Oriental liver fluke B66.1
Chinese B66.1
due to clonorchiasis B66.1
oriental B66.1
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Clonorchiasis
infection of the biliary passages with clonorchis sinensis, also called opisthorchis sinensis. it may lead to inflammation of the biliary tract, proliferation of biliary epithelium, progressive portal fibrosis, and sometimes bile duct carcinoma. extension to the liver may lead to fatty changes and cirrhosis. (from dorland, 27th ed)
Patient EducationClinical
Parasitic Diseases
Parasites are living things that use other living things - like your body - for food and a place to live. You can get them from contaminated food or water, a bug bite, or sexual contact. Some parasitic diseases are easily treated and some are not.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert B66.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About B66.1Overview
What is the ICD-10 code for clonorchiasis?
The ICD-10-CM code for clonorchiasis is B66.1 (sometimes written as B661). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is B66.1 (Other fluke infections) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report clonorchiasis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does B66.1 group to?
When clonorchiasis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 442, 441, 443, with relative weights from 0.6890 to 1.8226 depending on complications. Higher weights mean higher Medicare reimbursement.
Is B66.1 a CC or MCC?
CMS lists B66.1 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 8 closely related codes in its exclusion list.
What is the ICD-9 equivalent of B66.1?
Under the General Equivalence Mappings, clonorchiasis converts to ICD-9-CM 121.1 (clonorchiasis). The mapping is a direct match.
