2026 ICD-10-CM Diagnosis Code I31.9Disease of pericardium, unspecified

ICD-10-CM Codes›I00–I99›I30-I5A›I31

ICD-10-CM I31.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

I31.9 is a billable ICD-10-CM diagnosis code for disease of pericardium, unspecified. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pericarditis and pericardial disease.

Code Identity

ICD-10-CM Code
I31.9
Billable Status
Yes — Valid for Submission
Code Describes
Disease of pericardium, unspecified
Short Description
Disease of pericardium, unspecified
Same as the full description in the CMS dataset.
Parent Code
I31
Other diseases of pericardium

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI30-I5AOther forms of heart disease
CategoryI31Other diseases of pericardium
This CodeI31.9Disease of pericardium, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Camptodactyly, arthropathy, coxa-vara, pericarditis syndrome
  • Chest pain due to pericarditis
  • Chronic pericarditis
  • Disorder of pericardium
  • Drug-induced pericarditis
  • Familial pericarditis
  • Fixed flexion deformity finger
  • Hydralazine-induced pericarditis
  • Myopericarditis
  • Non-traumatic pneumopericardium
  • Pericardial anomaly
  • Pericardial defect
  • Pericarditis
  • Pericarditis caused by toxin
  • Pericarditis due to metabolic disease
  • Pericarditis secondary to collagen vascular disease
  • Pericarditis secondary to penetrating trauma
  • Pericarditis secondary to scleroderma
  • Pneumopericardium
  • Post-cardiac injury syndrome
  • Post-radiation pericarditis
  • Post-traumatic pericarditis
  • Procainamide-induced pericarditis
  • Subacute pericarditis

Tabular List NotesGuidance

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

Inclusion Terms

  • Pericarditis (chronic) NOS

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.

    • Pericarditis(with decompensation) (with effusion)
    • Pericarditis(with decompensation) (with effusion)
      • chronic (nonrheumatic)

Clinical ClassificationClinical

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

CCSR CIR006
Pericarditis and pericardial disease
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Pericarditis

    inflammation of the pericardium from various origins, such as infection, neoplasm, autoimmune process, injuries, or drug-induced. pericarditis usually leads to pericardial effusion, or constrictive pericarditis.

  • Pericarditis, Constrictive

    inflammation of the pericardium that is characterized by the fibrous scarring and adhesion of both serous layers, the visceral pericardium and the parietal pericardium leading to the loss of pericardial cavity. the thickened pericardium severely restricts cardiac filling. clinical signs include fatigue, muscle wasting, and weight loss.

  • Pericarditis, Tuberculous

    inflammation of the sac surrounding the heart (pericardium) due to mycobacterium tuberculosis infection. pericarditis can lead to swelling (pericardial effusion), compression of the heart (cardiac tamponade), and preventing normal beating of the heart.

  • Pneumopericardium

    presence of air or gas in the space between the heart and the pericardium. the degree of respiratory distress depends on the amount of trapped air and circulation blocked in the systemic and pulmonary veins.

  • Pericardium

    a conical fibro-serous sac surrounding the heart and the roots of the great vessels (aorta; venae cavae; pulmonary artery). pericardium consists of two sacs: the outer fibrous pericardium and the inner serous pericardium. the latter consists of an outer parietal layer facing the fibrous pericardium, and an inner visceral layer (epicardium) resting next to the heart, and a pericardial cavity between these two layers.

  • Acute Purulent Pericarditis|Acute purulent pericarditis

    a rare, life-threatening bacterial or fungal infection that is characterized by a severe and sudden onset and an accumulation of pus in the pericardial sac.

  • Acute Pericarditis

    acute inflammation of the pericardium.

  • Acute Pericarditis Related to COVID-19|Acute pericarditis

    acute pericarditis in a patient with probable or confirmed acute covid-19.

  • Acute Rheumatic Pericarditis

    inflammation of the pericardium in acute rheumatic heart disease.

  • Bacterial Pericarditis

    pericarditis that is caused by an infection with a bacterial agent.

  • Constrictive Pericarditis|Constrictive pericarditis

    a heart disorder in which the pericardial sac becomes thickened and fibrotic, tightening the myocardium and impeding the normal myocardial function.

  • Fungal Pericarditis

    pericarditis that is caused by an infection with a fungal agent.

  • Grade 1 Pericarditis, CTCAE|Grade 1 Pericarditis|Grade 1 Pericarditis

    asymptomatic, ecg or physical findings (e.g., rub) consistent with pericarditis

  • Grade 2 Pericarditis, CTCAE|Grade 2 Pericarditis|Grade 2 Pericarditis

    symptomatic pericarditis (e.g., chest pain)

  • Grade 3 Pericarditis, CTCAE|Grade 3 Pericarditis|Grade 3 Pericarditis

    pericarditis with physiologic consequences (e.g., pericardial constriction)

  • Grade 4 Pericarditis, CTCAE|Grade 4 Pericarditis|Grade 4 Pericarditis

    life-threatening consequences; urgent intervention indicated

  • Grade 5 Pericarditis, CTCAE|Grade 5 Pericarditis|Grade 5 Pericarditis

    death

  • Malignant Pericarditis|Pericarditis, Malignant

    pericarditis caused by the infiltration of the pericardium by a malignant neoplasm. the diagnosis is based on the cytological examination of pericardial fluid or the histologic examination of pericardial tissue.

  • Pericarditis

    an inflammatory process affecting the pericardium.

  • Pericarditis Associated with Post-Acute Sequelae of SARS-CoV-2 Infection|PASC Pericarditis|PASC pericarditis|Post-Acute Sequelae of COVID-19 Pericarditis

    pericarditis that started during probable or confirmed acute covid-19 and persisted beyond four weeks after the initial diagnosis of covid-19.

  • Pericarditis in Systemic Lupus Erythematosus|Pericarditis in systemic lupus erythematosus

    evidence of pericarditis in systemic lupus erythematosus.

  • Pericarditis, CTCAE|Pericarditis|Pericarditis|Pericarditis

    a disorder characterized by irritation to the layers of the pericardium (the protective sac around the heart).

  • ST Elevation Pericarditis by ECG Finding|ST ELEVATION PERICARDITIS|ST Elevation Pericarditis|ST Elevation Pericarditis by EKG Finding|ST elevation pericarditis

    an electrocardiographic finding of st elevation which is concave upwards, and which is often accompanied by pr segment depression. (cdisc)

  • Uremic Pericarditis

    inflammation of the pericardium associated with chronic kidney failure.

  • Viral Pericarditis

    pericarditis that is caused by an infection with a viral agent.

  • Pericardial Anomaly

    any abnormality involving the pericardium.

  • Pneumopericardium

    the presence of air in the pericardial cavity. causes include chest injury in adults, and respiratory distress syndrome in infants.

Patient EducationClinical

Pericardial Disorders

The pericardium is a membrane, or sac, that surrounds your heart. It holds the heart in place and helps it work properly. Problems with the pericardium include:

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert I31.9 to ICD-9-CMHistory

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

ICD-9-CM
423.9 Pericardial disease NOS
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 I31.9Overview

Is I31.9 (Other diseases of pericardium) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report disease of pericardium, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does I31.9 group to?

When disease of pericardium, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 314, 315, 316, with relative weights from 0.6821 to 2.0852 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of I31.9?

Under the General Equivalence Mappings, disease of pericardium, unspecified converts to ICD-9-CM 423.9 (pericardial disease NOS). 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.