What is ICD-10 code M31.31?

M31.31 is the ICD-10-CM diagnosis code for Wegener's granulomatosis with renal involvement. A serious autoimmune disease that causes inflammation of blood vessels and granulomas in the lungs, upper respiratory tract, and kidneys. M31.31 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. M31.31 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. M31.31 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. M31.31 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 M31.31?

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 M31.31, V28 maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders at RAF 0.617 while V24 mapped to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease at RAF 0.421. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting M31.31?

Always document the degree of renal involvement and any renal function impairment Link to appropriate codes for kidney disease if present Because M31.31 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 M31.31: Wegener's granulomatosis

ICD-10-CM Code View

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Code lookupM31.31Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Systemic connective tissue disorders (M30-M36)

M31.31

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

Wegener's granulomatosis with renal involvement

A serious autoimmune disease that causes inflammation of blood vessels and granulomas in the lungs, upper respiratory tract, and kidneys.

Buddy Insight

Wegener's granulomatosis with renal involvement represents the most severe form of this systemic necrotizing vasculitis, with significant risk of kidney failure and other organ damage.

CMS-HCC V28

Mapped

HCC 93

Rheumatoid Arthritis and Othe...

RAF 0.617

CMS-HCC V24

Mapped

HCC 40

Rheumatoid Arthritis and Infl...

RAF 0.421

ACA/HHS

Mapped

HCC 56

HHS-HCC 56

Varies by metal level

ESRD/PACE

Mapped

HCC 40

Rheumatoid Arthritis and Infl...

RAF 0.058

RXHCC

Mapped

HCC 84

Vasculitis and Other Autoimmu...

RAF 0.113

Code Book Path

Official

M31Other necrotizing vasculopathies

M31.3Wegener's granulomatosis

M31.31Wegener's granulomatosis with renal involvement

Inclusion Terms

Official

Granulomatosis with polyangiitis
Necrotizing respiratory granulomatosis

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M31.31 in this effective period.

Related Child Codes

Official

M31.30Wegener's granulomatosis without renal involvement

Includes

Official

ICD-10-CM does not list Includes notes for M31.31 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M31.31 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M31.31 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M31.31 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M31.31 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Clinical evidence of respiratory tract involvement

Documentation of renal involvement (hematuria, proteinuria, decreased GFR)

Biopsy evidence from affected organs

ANCA testing results

MEAT Support

HCC Buddy guidance

Clinical evidence of respiratory tract involvement

Documentation of renal involvement (hematuria, proteinuria, decreased GFR)

Biopsy evidence from affected organs

ANCA testing results

Audit Caution

HCC Buddy guidance

Using without renal involvement code when kidneys are affected

Missing the multi-organ systemic nature

Using only renal codes for kidney involvement

Confusing with other vasculitic syndromes

Common Mistakes

HCC Buddy guidance

M31.30 — Wegener's granulomatosis without renal involvement (when kidneys not affected)

M31.7 — Microscopic polyangiitis (different ANCA-associated vasculitis)

N05.9 — Unspecified nephritic syndrome (isolated renal disease)

J44.0 — Chronic obstructive pulmonary disease with acute lower respiratory infection

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 M31.31 an HCC code?

Yes. M31.31 (Wegener's granulomatosis with renal involvement) maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders under the CMS-HCC V28 risk adjustment model (and Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under V24), with a community non-dual aged RAF of 0.617. It is billable for payment year 2026.

Coder answer: M31.31 is billable and maps to V28 HCC 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: M31.31
Description: Wegener's granulomatosis with renal involvement
HCC (V28): HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders
RAF: 0.617
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders

0.617

V24HCC 40, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease

0.421

ESRDHCC 40, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease

0.058

RxHCCHCC 84, Vasculitis and Other Autoimmune Disorders

0.113

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 M31.31 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for M31.31

For M31.31 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 M31.31 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M31.31 is the ICD-10-CM diagnosis code for wegener's granulomatosis with renal involvement. A serious autoimmune disease that causes inflammation of blood vessels and granulomas in the lungs, upper respiratory tract, and kidneys. M31.31 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering systemic connective tissue disorders (m30-m36).

Under the CMS-HCC V28 risk adjustment model, M31.31 maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders (HCC 93) with a community, non-dual, aged base RAF weight of 0.617. Under the older CMS-HCC V24 model, M31.31 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 40) with a community, non-dual, aged base RAF weight of 0.421. 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.

Always document the degree of renal involvement and any renal function impairment. Because M31.31 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 M31.31 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Always document the degree of renal involvement and any renal function impairment
•Link to appropriate codes for kidney disease if present

Clinical Significance

Wegener's granulomatosis with renal involvement represents the most severe form of this systemic necrotizing vasculitis, with significant risk of kidney failure and other organ damage. The renal component indicates more extensive disease requiring aggressive immunosuppressive therapy and close monitoring.

Documentation Requirements

✓Clinical evidence of respiratory tract involvement
✓Documentation of renal involvement (hematuria, proteinuria, decreased GFR)
✓Biopsy evidence from affected organs
✓ANCA testing results
✓Assessment of extent of renal damage
✓Monitoring of kidney function over time
✓Treatment response in multiple organ systems
✓Coordination with nephrology services

Commonly Confused Codes

•M31.30: Wegener's granulomatosis without renal involvement (when kidneys not affected)
•M31.7: Microscopic polyangiitis (different ANCA-associated vasculitis)
•N05.9: Unspecified nephritic syndrome (isolated renal disease)
•J44.0: Chronic obstructive pulmonary disease with acute lower respiratory infection
•M30.0: Polyarteritis nodosa (different systemic vasculitis)