2026 ICD-10-CM Diagnosis Code J98.51Mediastinitis

ICD-10-CM Codes›J00–J99›J96-J99›J98

ICD-10-CM J98.51
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

J98.51 is a billable ICD-10-CM diagnosis code for mediastinitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 177 through 179, 791, 793. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 1 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Mediastinal disorders.

Code Identity

ICD-10-CM Code
J98.51
Billable Status
Yes — Valid for Submission
Code Describes
Mediastinitis
Short Description
Mediastinitis
Same as the full description in the CMS dataset.
Parent Code
J98.5
Diseases of mediastinum, not elsewhere classified

Code Classification

ChapterJ00–J99Diseases of the respiratory system
SectionJ96-J99Other diseases of the respiratory system
CategoryJ98Other respiratory disorders
This CodeJ98.51Mediastinitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute mediastinitis
  • Classical histoplasmosis mediastinal granuloma
  • Drug-induced granulomatous mediastinitis
  • Familial fibrous mediastinitis
  • Fibrous mediastinitis caused by radiation
  • Granulomatous mediastinitis
  • Hemorrhagic mediastinitis
  • Infection of lower respiratory tract and mediastinum
  • Infectious fibrous mediastinitis
  • Infectious granulomatous mediastinitis
  • Infectious mediastinitis
  • Inflammatory disorder of mediastinum
  • Pulmonary venous hypertension due to compression of pulmonary great vein
  • Pulmonary venous hypertension due to compression of pulmonary great vein by sclerosing mediastinitis
  • Sclerosing mediastinitis

Tabular List NotesGuidance

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

Code First

  • underlying condition, if applicable, such as postoperative mediastinitis T81

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR RSP015
Mediastinal disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Mediastinitis

    inflammation of the mediastinum, the area between the pleural sacs.

  • Infectious Mediastinitis|Mediastinal infection

    an acute or chronic infectious process affecting the mediastinum.

  • Mediastinitis

    an inflammatory process affecting the mediastinum.

  • Radiation-Induced Fibrous Mediastinitis

    fibrous mediastinitis arising due to radiation therapy.

Convert J98.51 to ICD-9-CMHistory

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

ICD-9-CM
519.2 Mediastinitis
Exact Match The mapping is direct, with no qualifiers.

Code History & ChangesHistory

Replacement J98.51 replaces the following previously assigned code(s):

  • J98.5 - Diseases of mediastinum, not elsewhere classified
FY 2019AddedAdded to the ICD-10-CM code setEffective October 1, 2018.
FY 2020–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About J98.51Overview

What is the ICD-10 code for mediastinitis?

The ICD-10-CM code for mediastinitis is J98.51 (sometimes written as J9851). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is J98.51 (Diseases of mediastinum, not elsewhere classified) a billable code?

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

What MS-DRG does J98.51 group to?

When mediastinitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 177, 178, 179, 791, 793, with relative weights from 0.7550 to 4.1696 depending on complications. Higher weights mean higher Medicare reimbursement.

Is J98.51 a CC or MCC?

CMS lists J98.51 as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 1 closely related codes in its exclusion list.

What is the ICD-9 equivalent of J98.51?

Under the General Equivalence Mappings, mediastinitis converts to ICD-9-CM 519.2 (mediastinitis). The mapping is a direct match.