What is ICD-10 code J85.3?

J85.3 is the ICD-10-CM diagnosis code for Abscess of mediastinum. A collection of pus in the mediastinum, which is the space in the chest between the lungs containing the heart and major vessels. It belongs to the ICD-10-CM chapter for diseases of the respiratory system (j00-j99). J85.3 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. J85.3 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. J85.3 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. J85.3 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for J85.3?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For J85.3, V28 maps to Empyema, Lung Abscess at RAF 0.204 while V24 mapped to Pneumococcal Pneumonia, Empyema, Lung Abscess at RAF 0.130. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting J85.3?

Mediastinal abscess is a serious condition; verify location is mediastinum and not lung parenchyma Document the source of infection (esophageal perforation, post-surgical, etc.) if known Because J85.3 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

2026 ICD-10-CM J85.3: Abscess of mediastinum

ICD-10-CM Code View

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Code lookupJ85.3Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the respiratory system (J00-J99) / Suppurative and necrotic conditions of the lower respiratory tract (J85-J86)

J85.3

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Abscess of mediastinum

A collection of pus in the mediastinum, which is the space in the chest between the lungs containing the heart and major vessels.

Buddy Insight

Abscess of mediastinum is a rare but extremely serious infection involving the space between the lungs containing the heart, great vessels, esophagus, and trachea.

CMS-HCC V28

Mapped

HCC 283

Empyema, Lung Abscess

RAF 0.204

CMS-HCC V24

Mapped

HCC 115

Pneumococcal Pneumonia, Empye...

RAF 0.130

ACA/HHS

Mapped

HCC 163

HHS-HCC 163

Varies by metal level

ESRD/PACE

Mapped

HCC 115

Pneumococcal Pneumonia, Empye...

RAF 0.030

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

J85Abscess of lung and mediastinum

J85.3Abscess of mediastinum

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for J85.3 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for J85.3 in this effective period.

Related Child Codes

Official

J85.0Gangrene and necrosis of lung

J85.1Abscess of lung with pneumonia

J85.2Abscess of lung without pneumonia

Includes

Official

ICD-10-CM does not list Includes notes for J85.3 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for J85.3 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for J85.3 in this effective period.

Use Additional

Official

code (B95-B97) to identify infectious agent.

Code Also

Official

ICD-10-CM does not list Code Also instructions for J85.3 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

CT chest confirming fluid collection with rim enhancement in the mediastinal space

Identification of the source of infection (esophageal perforation, dental/pharyngeal infection, post-surgical, direct spread)

Culture and organism identification from drainage or surgical specimen

Documentation of surgical intervention (mediastinal drainage, debridement) or percutaneous drainage

MEAT Support

HCC Buddy guidance

CT chest confirming fluid collection with rim enhancement in the mediastinal space

Identification of the source of infection (esophageal perforation, dental/pharyngeal infection, post-surgical, direct spread)

Culture and organism identification from drainage or surgical specimen

Documentation of surgical intervention (mediastinal drainage, debridement) or percutaneous drainage

Audit Caution

HCC Buddy guidance

Confusing mediastinal location with pleural (empyema) or parenchymal (lung abscess) infections — anatomy determines the code

Failing to identify and code the underlying cause (esophageal perforation, dental infection, post-surgical complication)

Not capturing associated sepsis which commonly accompanies mediastinal abscess

Using this code for mediastinal lymphadenopathy or mediastinal masses which are not abscesses

Common Mistakes

HCC Buddy guidance

J85.1/J85.2 — Abscess of lung is located in the lung parenchyma, not the mediastinal space

J86.0/J86.9 — Pyothorax involves the pleural space, not the mediastinum

I30.1 — Infective pericarditis may co-occur with mediastinal abscess but is a separate diagnosis

K22.3 — Perforation of esophagus may be the cause and should be coded separately if present

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is J85.3 an HCC code?

Yes. J85.3 (Abscess of mediastinum) maps to Empyema, Lung Abscess under the CMS-HCC V28 risk adjustment model (and Pneumococcal Pneumonia, Empyema, Lung Abscess under V24), with a community non-dual aged RAF of 0.204. It is billable for payment year 2026.

Coder answer: J85.3 is billable and maps to V28 HCC 283, Empyema, Lung Abscess. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: J85.3
Description: Abscess of mediastinum
HCC (V28): HCC 283 — Empyema, Lung Abscess
RAF: 0.204
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 283, Empyema, Lung Abscess

0.204

V24HCC 115, Pneumococcal Pneumonia, Empyema, Lung Abscess

0.130

ESRDHCC 115, Pneumococcal Pneumonia, Empyema, Lung Abscess

0.030

Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work J85.3 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for J85.3

For J85.3 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed J85.3 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

J85.3 is the ICD-10-CM diagnosis code for abscess of mediastinum. A collection of pus in the mediastinum, which is the space in the chest between the lungs containing the heart and major vessels. J85.3 sits in the ICD-10-CM chapter for diseases of the respiratory system (j00-j99), within the section covering suppurative and necrotic conditions of the lower respiratory tract (j85-j86).

Under the CMS-HCC V28 risk adjustment model, J85.3 maps to Empyema, Lung Abscess (HCC 283) with a community, non-dual, aged base RAF weight of 0.204. Under the older CMS-HCC V24 model, J85.3 maps to Pneumococcal Pneumonia, Empyema, Lung Abscess (HCC 115) with a community, non-dual, aged base RAF weight of 0.130. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Mediastinal abscess is a serious condition; verify location is mediastinum and not lung parenchyma. Because J85.3 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for J85.3 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Mediastinal abscess is a serious condition; verify location is mediastinum and not lung parenchyma
•Document the source of infection (esophageal perforation, post-surgical, etc.) if known

Clinical Significance

Abscess of mediastinum is a rare but extremely serious infection involving the space between the lungs containing the heart, great vessels, esophagus, and trachea. Common causes include esophageal perforation, descending necrotizing mediastinitis from odontogenic infections, and post-surgical complications. This diagnosis indicates life-threatening illness requiring emergent surgical intervention and carries high mortality.

Documentation Requirements

✓CT chest confirming fluid collection with rim enhancement in the mediastinal space
✓Identification of the source of infection (esophageal perforation, dental/pharyngeal infection, post-surgical, direct spread)
✓Culture and organism identification from drainage or surgical specimen
✓Documentation of surgical intervention (mediastinal drainage, debridement) or percutaneous drainage
✓Monitoring for complications including sepsis, great vessel erosion, and pericarditis

Commonly Confused Codes

•J85.1/J85.2: Abscess of lung is located in the lung parenchyma, not the mediastinal space
•J86.0/J86.9: Pyothorax involves the pleural space, not the mediastinum
•I30.1: Infective pericarditis may co-occur with mediastinal abscess but is a separate diagnosis
•K22.3: Perforation of esophagus may be the cause and should be coded separately if present