Pulmonary Fibrosis — Clinical Documentation Guide (2026)

🔍 Definition

Pulmonary fibrosis is a chronic, progressive, and ultimately fatal interstitial lung disease (ILD) characterized by the pathological accumulation of fibrotic scar tissue within the pulmonary parenchyma. The fibrotic process replaces normal alveolar architecture with dense connective tissue, resulting in irreversible loss of lung compliance and impaired gas exchange. The umbrella term encompasses a heterogeneous group of more than 200 distinct ILD subtypes, ranging from well-defined entities such as idiopathic pulmonary fibrosis (IPF) to secondary fibrotic processes arising from connective tissue diseases, occupational exposures, hypersensitivity pneumonitis, and drug toxicity.

For ICD-10-CM coding purposes under FY2026 Official Guidelines, pulmonary fibrosis codes reside primarily in category J84 – Other interstitial pulmonary diseases, with closely related conditions coded across J60–J70 (pneumoconioses and occupational lung diseases), D86 (sarcoidosis), and J80 (acute respiratory distress syndrome). Selecting the most specific code within J84 is paramount for accurate HCC risk adjustment and MS-DRG assignment.

🗂️ Alternative Terminology

The clinical and lay terminology for pulmonary fibrosis is highly variable. Coders must map colloquial documentation to the correct ICD-10-CM subcategory.

🩺 Signs & Symptoms

Pulmonary fibrosis presents insidiously; symptoms are often attributed to other conditions (deconditioning, cardiac disease) for months to years before diagnosis. Key clinical features include:

• Progressive exertional dyspnea — the cardinal symptom, initially on exertion and advancing to rest in severe disease
• Dry, nonproductive cough — persistent and often refractory to standard antitussives
• Bibasilar inspiratory crackles (“Velcro” crackles) — present in ~80% of IPF patients on auscultation
• Digital clubbing — present in up to 50% of IPF cases; less common in other ILD subtypes
• Hypoxemia — exertional desaturation (SaO₂ <90% on 6-minute walk test) and resting hypoxemia in advanced disease
• Reduced exercise tolerance — 6-minute walk distance (6MWD) is a validated outcome measure per ATS/ERS/JRS/ALAT IPF guidelines
• Weight loss and fatigue — systemic manifestations in progressive disease
• Signs of pulmonary hypertension — elevated JVP, right ventricular heave, loud P2 in advanced fibrosis (code separately with I27.2x)
• Acute exacerbation of IPF (AE-IPF) — rapid respiratory deterioration with new bilateral ground-glass opacities superimposed on UIP background; high mortality

🧭 Differential Diagnosis

Establishing the correct ILD subtype requires multidisciplinary discussion (MDD) integrating clinical history, HRCT pattern, BAL findings, and—when performed—surgical lung biopsy results. The following differential diagnoses are relevant for coding and CDI purposes.

📋 Clinical Indicators for Coders/CDI

The following clinical indicators, when present in the medical record, support specific ICD-10-CM code assignment and justify higher-specificity reporting:

🦴 Anatomy & Pathophysiology

Pulmonary fibrosis results from aberrant wound healing within the lung parenchyma. Under normal circumstances, alveolar epithelial injury triggers a regulated repair cascade involving type II pneumocytes, fibroblasts, and myofibroblasts. In pathological fibrosis, this process becomes dysregulated and self-perpetuating.

Normal Lung Anatomy Relevant to ILD

The lung’s gas-exchanging unit — the alveolus — is lined by type I pneumocytes (thin, covering ~95% of the surface for gas exchange) and type II pneumocytes (cuboidal, producing surfactant). The alveolar interstitium contains capillary endothelium, fibroblasts, mast cells, macrophages, and a minimal extracellular matrix. In health, the interstitium is barely visible on imaging.

Pathological Mechanisms in IPF

The current paradigm frames IPF as an epithelial-driven fibrotic disease. Repeated microinjuries (from gastric aspiration, viral infection, particulates, or genetic predisposition in carriers of MUC5B or TERT/TERC telomere gene variants) cause type II pneumocyte apoptosis and senescence. This releases profibrotic mediators — TGF-β1, CTGF, PDGF — that activate resident fibroblasts and circulating fibrocytes to differentiate into myofibroblasts. Myofibroblasts deposit excessive collagen I and III, and fail to undergo apoptosis, resulting in the progressive accumulation of fibrotic foci seen histologically in UIP.

Histopathological Patterns

• UIP (Usual Interstitial Pneumonia): Temporal heterogeneity with fibroblastic foci, dense fibrosis, honeycombing, architectural distortion; subpleural and basal predominance. Correlates with J84.112 when idiopathic.
• NSIP (Nonspecific Interstitial Pneumonia): Temporally homogeneous fibrosis or ground-glass opacity; less honeycombing; better prognosis. Idiopathic form → J84.113; CTD-associated → J99 with primary CTD code first.
• DIP (Desquamative Interstitial Pneumonia): Diffuse alveolar macrophage accumulation; strongly associated with smoking → J84.117.
• RB-ILD: Respiratory bronchiolitis with peribronchiolar macrophage accumulation → J84.115.
• COP (Cryptogenic Organizing Pneumonia): Intraluminal fibroblastic plugs (Masson bodies) filling alveolar ducts and alveoli → J84.116.

Functional Consequences

Progressive fibrosis reduces lung compliance, causing a restrictive ventilatory defect (reduced FVC, reduced TLC). Thickening of the alveolar-capillary membrane impairs diffusion of oxygen (reduced DLCO/KCO). Hypoxemia worsens with exertion first, then occurs at rest in severe disease. Fibrosis-associated pulmonary hypertension (Group 3 PH) develops in 30–40% of advanced IPF patients and worsens prognosis significantly (code I27.22 or I27.29 separately).

💊 Medication Impact / Treatment

Pharmacological management of pulmonary fibrosis is primarily aimed at slowing disease progression rather than reversing established fibrosis. Two antifibrotic agents are FDA-approved for IPF; nintedanib has also received approval for systemic sclerosis-ILD and progressive pulmonary fibrosis (which encompasses J84.170).

Antifibrotic Agents (Impact on Coding & Documentation)

• Nintedanib (Ofev®): Tyrosine kinase inhibitor targeting PDGFR, FGFR, and VEGFR; approved for IPF (J84.112), SSc-ILD (M34.81 + J99), and progressive pulmonary fibrosis (J84.170). HCPCS J7686 for injectable formulation; oral formulation typically billed via NDC for Medicare Part D. Presence in the medication record is a strong CDI indicator supporting J84.112 or J84.170 coding.
• Pirfenidone (Esbriet®): Antifibrotic and anti-inflammatory; approved for IPF. HCPCS J3490 (unlisted drug) when not otherwise specified; billed via NDC for Medicare Part D oral administration. Presence supports J84.112 assignment.

Supportive Therapies

• Supplemental oxygen: Prescribed for resting SaO₂ ≤88% or exertional desaturation. HCPCS E1390 (stationary O₂ concentrator), E0433 (portable liquid O₂ system). Document Z99.81 (dependence on supplemental oxygen) when chronic O₂ >15 hr/day — critical for RAF and quality measures.
• Pulmonary rehabilitation: CPT 94005, G0424; improves exercise capacity and quality of life in ILD.
• Lung transplantation: Definitive therapy for eligible patients; coding shifts to post-transplant ICD-10-CM codes (Z94.2, T86.81x); bilateral single-lung transplant most common for IPF.
• Immunosuppression for CTD-ILD: Mycophenolate mofetil, azathioprine, rituximab for SSc-ILD or RA-ILD; document underlying CTD and lung manifestation.
• Systemic corticosteroids: Used for COP (J84.116), DIP (J84.117), LIP (J84.2), acute exacerbation of IPF; NOT recommended for stable IPF (can increase mortality per ATS/ERS IPF Guidelines).

Preview ends here. The full guide continues with FY2026 ICD-10-CM code sets, CPT surgical coding, MS-DRG mapping, reimbursement guidance, CDI query templates, and an audit checklist — all available to CCO Members.

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📘 ICD-10-CM Guidelines (FY2026)

The following Official Coding and Reporting Guidelines, per the FY2026 ICD-10-CM Official Guidelines (effective October 1, 2025), govern pulmonary fibrosis code assignment:

Etiology/Manifestation Coding (Guideline I.C.)

When pulmonary fibrosis or ILD occurs as a manifestation of a systemic disease classified elsewhere, the underlying disease is sequenced first and the lung manifestation coded additionally:

• Systemic sclerosis with lung involvement: Code M34.81 first, then J99 for the ILD/fibrosis manifestation. ICD-10-CM Tabular instructs “Code also associated conditions” under J84.17x.
• Rheumatoid arthritis with ILD: Code the specific RA code first (M05.10–M05.19 for RA with rheumatoid lung disease), then J99 if additional interstitial coding is needed. Note that M05.1x already captures rheumatoid lung disease.
• J84.170 – Interstitial lung disease with progressive fibrotic phenotype in diseases classified elsewhere: This FY2025 new code requires the underlying disease to be coded first (e.g., M34.81 for SSc, J67.x for HP). Use J84.170 when non-IPF ILD demonstrates progressive fibrotic behavior with documented FVC decline.
• J84.178 – Other ILD in diseases classified elsewhere: Code the underlying condition first.

Principal Diagnosis Selection

For inpatient encounters, when pulmonary fibrosis (e.g., acute exacerbation of IPF) is the reason for admission, J84.112 is the principal diagnosis. Complicating conditions such as acute respiratory failure (J96.0x) are coded additionally per UHDDS principal diagnosis definition.

Specificity Requirements

Per General Guideline I.A.3 (Level of Detail in Coding), the coder must use the most specific code available. Using J84.9 (Interstitial pulmonary disease, unspecified) or J84.10 (Pulmonary fibrosis, unspecified) when documentation supports a more specific code (e.g., J84.112 IPF based on HRCT UIP pattern without identifiable cause) constitutes undercoding. Query the physician when documentation is ambiguous.

Oxygen Dependence

Z99.81 (Dependence on supplemental oxygen) should be assigned as an additional code whenever a patient is on chronic supplemental oxygen (typically ≥15 hours/day) per Official Guidelines Section I.C.21.c.17. This is a significant HCC/risk adjustment code and is frequently undercoded in pulmonary fibrosis patients.

FY2025/FY2026 Changes Relevant to Pulmonary Fibrosis

• J84.170 (NEW FY2025, active FY2026): “Interstitial lung disease with progressive fibrotic phenotype in diseases classified elsewhere” — created to capture the progressive fibrosing ILD (PF-ILD) concept aligning with nintedanib’s expanded FDA approval. Requires underlying disease coded first.
• No other J84 code additions specific to pulmonary fibrosis in FY2026; verify at CMS FY2026 ICD-10-CM files.

🔢 ICD-10-CM Code Set (FY2026)

All codes below are valid for FY2026 (effective October 1, 2025). Verify currency at the CMS FY2026 ICD-10-CM Tabular.

🔎 Indexing

Use the ICD-10-CM Alphabetic Index and Tabular List to verify all codes. Key index pathways for pulmonary fibrosis:

• Fibrosis, fibrotic → lung (atrophic) (chronic) (confluent) (massive) (perialveolar) (peribronchial): → J84.10 (unspecified); subterm “idiopathic” → J84.112
• Pneumonitis, interstitial → idiopathic nonspecific: J84.113
• Pneumonitis → organizing (cryptogenic): J84.116
• Lymphangioleiomyomatosis: → J84.81
• Histiocytosis → pulmonary Langerhans cell: → J84.82
• Disease, lung, interstitial → with progressive fibrotic phenotype: → J84.170 (code first underlying cause)
• Disease, lung, interstitial → in diseases classified elsewhere: → J84.178
• Sarcoidosis, lung / pulmonary: → D86.0
• Dependence → oxygen: → Z99.81
• Sclerosis, systemic → with lung involvement: M34.81 (Tabular note: code also J99 or J84.17x)
• Arthritis, rheumatoid → lung: M05.10–M05.19 (laterality by site of arthritis)

🏥 CPT (2026)

The following CPT codes are relevant to the diagnosis, monitoring, and procedural management of pulmonary fibrosis. All codes are CY2026 CPT.

🧾 HCPCS (2026)

The following HCPCS Level II codes are relevant to durable medical equipment and pharmaceutical billing for pulmonary fibrosis. Verify current codes at CMS HCPCS annual updates.

📚 AHA Coding Clinic (Recent Guidance)

The following AHA Coding Clinic for ICD-10-CM/PCS references provide official guidance relevant to pulmonary fibrosis coding. Note: Coding Clinic issues are copyrighted by the AHA; summaries are provided here for educational reference.

• Coding Clinic, Q4 2017: Addressed coding for usual interstitial pneumonitis pattern — confirmed that UIP on HRCT without known cause, diagnosed clinically as IPF, should be coded J84.112 and not J84.10. Physician query is required if documentation only states “UIP” without an associated clinical diagnosis.
• Coding Clinic, Q3 2018: Clarified etiology/manifestation sequencing for connective tissue disease-associated ILD — confirmed that underlying CTD (e.g., M34.81 systemic sclerosis with lung involvement) must be sequenced before the ILD manifestation code (J99 or J84.178).
• Coding Clinic, Q1 2021: Guidance on progressive fibrosing ILD (PF-ILD) pre-FY2025 code creation — coders were instructed to use J84.89 (other specified ILD) when the physician documented “progressive fibrosing ILD” in non-IPF patients prior to the creation of J84.170.
• Coding Clinic, FY2025 cycle: Introduction of J84.170 with guidance on code first requirements and documentation expectations for “progressive fibrotic phenotype” in non-IPF ILD. Review the FY2025 AHA Coding Clinic issues for complete guidance on J84.170 application.

💰 HCC / Risk Adjustment (v28)

Under the CMS-HCC Model v28 (fully implemented in 2025), the majority of pulmonary fibrosis codes map to HCC 280 – Pulmonary Fibrosis and Other Chronic Lung Disorders, which carries a Risk Adjustment Factor (RAF) of approximately 0.204 for community-dwelling Medicare Advantage beneficiaries.

HCC v28 vs. v24 Transition Notes

The CMS-HCC v28 model, fully phased in for 2025, restructured pulmonary categories. CMS reorganized HCC categories to create HCC 280 as a consolidated chronic lung disorders category, which absorbs what were previously split across v24 categories. Verify current RAF values using the CMS HCC software tool for the current payment year, as segment-specific RAFs vary by community vs. institutional status and low-income subsidy status.

✍️ CDI Query Templates

All query templates below follow AHIMA/ACDIS CDI Query Practice Brief standards: non-leading, multiple-choice format, with clinical basis provided. Queries should be submitted through approved facility query platforms and documented in the medical record per facility policy.

🧑‍⚕️ Treatments (Clinical)

Clinical management of pulmonary fibrosis is multidisciplinary and tailored to the specific ILD subtype, disease severity, and patient comorbidities. Evidence-based treatment summaries are derived from current society guidelines including ATS/ERS/JRS/ALAT IPF Guidelines and the ATS ILD clinical resources.

Antifibrotic Pharmacotherapy

• Nintedanib (Ofev®): FDA-approved for IPF (2014), SSc-ILD (2019), and progressive pulmonary fibrosis (2020). Mechanism: tyrosine kinase inhibitor (PDGFR, VEGFR, FGFR). Reduces annual FVC decline by ~50% vs placebo. Dose: 150 mg orally twice daily with food. Key AE: diarrhea (62%), nausea, hepatotoxicity (monitor LFTs).
• Pirfenidone (Esbriet®): FDA-approved for IPF (2014). Mechanism: pleiotropic anti-inflammatory and antifibrotic. Reduces FVC decline and progression. Dose: titrated to 801 mg TID. Key AE: photosensitivity, GI disturbance, hepatotoxicity.

Non-Pharmacologic Interventions

• Supplemental Oxygen Therapy: Prescribed per Medicare LCD L33797 criteria: resting SaO₂ ≤88%, or exercise-induced desaturation to ≤88% with documented need. Long-term oxygen therapy (LTOT) improves survival in resting hypoxemia.
• Pulmonary Rehabilitation: 6–8 week supervised program improves 6MWD, dyspnea scores, and health-related QoL. Now a Medicare-covered benefit (HCPCS G0424) for ILD patients meeting moderate-to-severe criteria.
• Lung Transplantation: Only curative option; bilateral sequential lung transplant preferred for IPF. Median post-transplant survival for IPF is 4–5 years. Requires UNOS listing criteria and multidisciplinary evaluation. ICD-10-CM: Z94.2 (lung transplant status) post-procedure; T86.81x for complications.
• Antacid Therapy: Per conditional recommendation in ATS IPF guidelines — many centers treat subclinical gastroesophageal reflux (silent aspiration as microinjury trigger) with PPIs; data mixed but practice widespread.

CTD-ILD Specific Treatments

• SSc-ILD: Mycophenolate mofetil (MMF) is the first-line immunosuppressant (per Scleroderma Lung Study I & II); nintedanib add-on per SENSCIS trial. Rituximab (anti-CD20) for refractory disease.
• RA-ILD: Optimization of RA disease control; MTX controversy (may be fibrogenic); MMF, azathioprine, or rituximab; pirfenidone under investigation.
• HP (fibrotic): Antigen avoidance is paramount; systemic corticosteroids for initial management; MMF or azathioprine for steroid-sparing; nintedanib if progressive fibrotic phenotype (J84.170).

Emerging Therapies (FY2026 Horizon)

• Pamrevlumab (anti-CTGF): Monoclonal antibody; FDA Breakthrough Therapy for IPF; Phase 3 data pending.
• Inhaled treprostinil (Tyvaso®): FDA-approved for PH-ILD (Group 3 PH in ILD, per INCREASE trial); relevant when J84.112 is complicated by I27.22 (PH due to ILD). HCPCS J3285 (treprostinil inhalation).
• Autotaxin inhibitors, integrin αvβ6/αvβ1 inhibitors: Phase 2 trials ongoing; watch for new HCPCS J-codes in CY2027.

🎓 Patient Education / Summary

The following patient-facing summary is intended as a resource for CDI specialists, coders, and care coordinators when educating patients or preparing documentation for patient communication. Clinical accuracy is maintained while using accessible language.

What Is Pulmonary Fibrosis?

Pulmonary fibrosis (PF) is a lung disease that causes scarring (fibrosis) in the lungs. As scar tissue builds up, the lungs become stiff and it becomes harder to breathe and for oxygen to pass from the lungs into the blood. The most common form is idiopathic pulmonary fibrosis (IPF) — “idiopathic” means the cause is unknown. Other forms are linked to autoimmune diseases, occupational exposures, or other lung conditions. There is currently no cure, but treatments can slow the disease and help patients feel better.

Understanding Your Diagnosis Code

Your doctor uses specific codes to describe your diagnosis. For pulmonary fibrosis, the most common codes include:

• J84.112 – Idiopathic Pulmonary Fibrosis (IPF): The most specific code for IPF when no cause has been found.
• J84.10 – Pulmonary fibrosis, unspecified: Used when the exact type has not been determined.
• Z99.81 – Dependence on supplemental oxygen: If you use oxygen therapy daily, this code should appear in your record.

Accurate coding helps ensure your health plan covers the right treatments and that your care team communicates your full health picture.

Questions to Ask Your Doctor

• What specific type of pulmonary fibrosis do I have?
• Has my HRCT (lung scan) shown a UIP or NSIP pattern?
• Should I be on an antifibrotic medication (nintedanib or pirfenidone)?
• Do I qualify for pulmonary rehabilitation?
• Am I a candidate for a lung transplant evaluation?
• Should I be on supplemental oxygen?

Trusted Resources for Patients

• Pulmonary Fibrosis Foundation (PFF) — patient support, clinical trial listings, care center locator
• NIH National Heart, Lung, and Blood Institute – IPF
• American Lung Association – Pulmonary Fibrosis
• American Thoracic Society – IPF Patient Information

About this Guide

This Clinical Documentation Guide is published by CCO Academy and is intended for credentialed coding, CDI, and clinical documentation professionals. Content is updated for FY2026 ICD-10-CM (effective October 1, 2025). All code assignments should be verified against the official ICD-10-CM Tabular List, AHA Coding Clinic, and applicable payer-specific policies. This guide does not constitute legal, medical, or compliance advice.

Last reviewed: April 2026 · Next scheduled review: October 2026 (FY2027 update)