2026 ICD-10-CM Diagnosis Code I31.31Malignant pericardial effusion in diseases classified elsewhere

ICD-10-CM Codes›I00–I99›I30-I5A›I31

ICD-10-CM I31.31
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I31.31 is a billable ICD-10-CM diagnosis code for malignant pericardial effusion in diseases classified elsewhere. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 314 through 316. The code is a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as malignant neoplasm of pericardium. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pericarditis and pericardial disease.

Code Identity

ICD-10-CM Code
I31.31
Billable Status
Yes — Valid for Submission
Code Describes
Malignant pericardial effusion in diseases classified elsewhere
Short Description
Malignant pericardial effusion in diseases classd elswhr
Parent Code
I31.3
Pericardial effusion (noninflammatory)

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI31Other diseases of pericardium
This CodeI31.31Malignant pericardial effusion in diseases classified elsewhere

Code EditsBilling

Medicare Code Editor checks that affect claim validity for I31.31.

Manifestation diagnoses
Manifestation codes describe the manifestation of an underlying disease, not the disease itself, and therefore should not be used as a principal diagnosis.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Malignant neoplasm of pericardium
  • Malignant pericardial effusion
  • Pericardial effusion co-occurrent and due to malignant neoplasm of pericardium

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Code First

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.

    • Effusion
      • pericardium, pericardial (noninflammatory)
        • malignant, in disease classified elsewhere

Clinical ClassificationClinical

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

CCSR CIR006
Pericarditis and pericardial disease
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • Malignant Pericardial Effusion

    presence of fluid in the pericardial space as a complication of malignant disease.

Patient EducationClinical

Cardiopulmonary Syndromes (PDQ®)

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Code History & ChangesHistory

Replacement I31.31 replaces the following previously assigned code(s):

  • I31.3 - Pericardial effusion (noninflammatory)
FY 2023AddedAdded to the ICD-10-CM code setEffective October 1, 2022.
FY 2024–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About I31.31Overview

Is I31.31 (Pericardial effusion (noninflammatory)) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report malignant pericardial effusion in diseases classified elsewhere on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does I31.31 group to?

On inpatient claims, malignant pericardial effusion in diseases classified elsewhere maps to MS-DRG 314, 315, 316, with relative weights from 0.6821 to 2.0852 depending on complications. Higher weights mean higher Medicare reimbursement.

Can I31.31 be a principal diagnosis?

No. This is a manifestation code: malignant pericardial effusion in diseases classified elsewhere describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.