2026 ICD-10-CM Diagnosis Code R83.6Abnormal cytological findings in cerebrospinal fluid

ICD-10-CM Codes›R00–R99›R83-R89›R83

ICD-10-CM R83.6
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

R83.6 is a billable ICD-10-CM diagnosis code for abnormal cytological findings in cerebrospinal fluid. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). As a symptom code, it should not be used as a principal diagnosis once a related definitive diagnosis has been established. Coders also document this condition as abnormal cytological findings in CSF. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Abnormal findings without diagnosis.

Code Identity

ICD-10-CM Code
R83.6
Billable Status
Yes — Valid for Submission
Code Describes
Abnormal cytological findings in cerebrospinal fluid
Short Description
Abnormal cytological findings in cerebrospinal fluid
Same as the full description in the CMS dataset.
Parent Code
R83
Abnormal findings in cerebrospinal fluid

Code Classification

ChapterR00–R99Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
SectionR83-R89Abnormal findings on examination of other body fluids, substances and tissues, without diagnosis
CategoryR83Abnormal findings in cerebrospinal fluid
This CodeR83.6Abnormal cytological findings in cerebrospinal fluid

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Abnormal cytological findings in CSF
  • Cerebrospinal fluid cell content - finding
  • Cerebrospinal fluid cell content above reference range
  • Cerebrospinal fluid lymphocytosis
  • CSF: erythrocytosis
  • CSF: polymorphonuclear leukocytosis
  • Pleocytosis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Abnormal, abnormality, abnormalities
      • cerebrospinal fluid
        • cytology
    • Abnormal, abnormality, abnormalities
      • Papanicolaou (smear)
        • cerebrospinal fluid

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR SYM017
Abnormal findings without diagnosis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Pleocytosis

    abnormally high cell count in a body fluid.

Convert R83.6 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
792.0 Abn fnd-cerebrospinal fl
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About R83.6Overview

Is R83.6 (Abnormal findings in cerebrospinal fluid) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report abnormal cytological findings in cerebrospinal fluid on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Can R83.6 be a principal diagnosis?

Use it with care. This is a symptom code, so once a definitive diagnosis explaining the abnormal cytological findings in cerebrospinal fluid is established, that condition takes the principal position instead.

What is the ICD-9 equivalent of R83.6?

Under the General Equivalence Mappings, abnormal cytological findings in cerebrospinal fluid converts to ICD-9-CM 792.0 (abn fnd-cerebrospinal fl). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.