What is ICD-10 code I77.811?

I77.811 is the ICD-10-CM diagnosis code for Abdominal aortic ectasia. It belongs to the ICD-10-CM chapter for diseases of the circulatory system (i00-i99). I77.811 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I77.811 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. I77.811 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. I77.811 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 I77.811?

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. I77.811 was a payment HCC under V24 (Vascular Disease) but the V28 recalibration removed it from the risk adjustment model. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting I77.811?

Distinguish between ectasia (mild dilation) and aneurysm (larger dilation); ectasia codes are used for smaller dilations that don't meet aneurysm criteria Document the location (abdominal) and any associated symptoms or complications, as these may affect severity assessment and treatment decisions Because I77.811 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 I77.811: Abdominal aortic ectasia

ICD-10-CM Code View

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Code lookupI77.811Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Diseases of arteries, arterioles and capillaries (I70-I79)

I77.811

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

Abdominal aortic ectasia

This condition involves an abnormal widening or ballooning of the abdominal aorta (the main blood vessel in the abdomen), but it is smaller than what would be classified as a true aneurysm. It represents a localized dilation of the aortic wall that requires monitoring to prevent progression.

Buddy Insight

Abdominal aortic ectasia represents mild dilation of the abdominal aorta below the aneurysm threshold (typically less than 3 cm).

CMS-HCC V28

N/A

—

Not risk-adjusted for this model/period.

Not mapped

CMS-HCC V24

Mapped

HCC 108

Vascular Disease

RAF 0.288

ACA/HHS

N/A

—

Not risk-adjusted for this model/period.

Not mapped

ESRD/PACE

Mapped

HCC 108

Vascular Disease

RAF 0.073

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

I77.8Other specified disorders of arteries and arterioles

I77.81Aortic ectasia

I77.811Abdominal aortic ectasia

Inclusion Terms

Official

Ectasis aorta

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I77.811 in this effective period.

Related Child Codes

Official

I77.810Thoracic aortic ectasia

I77.812Thoracoabdominal aortic ectasia

I77.819Aortic ectasia, unspecified site

Includes

Official

ICD-10-CM does not list Includes notes for I77.811 in this effective period.

Excludes 1

Official

aortic aneurysm and dissection (I71.-)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I77.811 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I77.811 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for I77.811 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Imaging confirmation with abdominal aortic diameter measurements (ultrasound, CT, or magnetic resonance imaging)

Documentation distinguishing ectasia from aneurysm based on size criteria

Surveillance plan including imaging follow-up intervals

Assessment of cardiovascular risk factors including smoking, hypertension, and family history

MEAT Support

HCC Buddy guidance

Imaging confirmation with abdominal aortic diameter measurements (ultrasound, CT, or magnetic resonance imaging)

Documentation distinguishing ectasia from aneurysm based on size criteria

Surveillance plan including imaging follow-up intervals

Assessment of cardiovascular risk factors including smoking, hypertension, and family history

Audit Caution

HCC Buddy guidance

Confusing abdominal aortic ectasia with abdominal aortic aneurysm — check measurements against threshold

Using unspecified site code (I77.819) when the abdominal location is clearly documented

Failing to update the code to aneurysm if follow-up imaging shows progression beyond aneurysm threshold

Not distinguishing from infrarenal vs. suprarenal location when documented

Common Mistakes

HCC Buddy guidance

I71.4 — Abdominal aortic aneurysm without rupture: use when dilation meets aneurysm threshold (3 cm or greater)

I77.810 — Thoracic aortic ectasia: different anatomic location

I77.812 — Thoracoabdominal aortic ectasia: use when both thoracic and abdominal segments are dilated

I77.819 — Aortic ectasia, unspecified site: less specific; use I77.811 when abdominal location is documented

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 I77.811 an HCC code?

Yes. I77.811 maps to Vascular Disease under the V24 model but is not retained in V28.

Code: I77.811
Description: Abdominal aortic ectasia
HCC (V28): No CMS-HCC V28 mapping
RAF: —
Billable: Yes
Payment year: 2026

HCC Category Mapping

V24HCC 108, Vascular Disease

0.288

ESRDHCC 108, Vascular Disease

0.073

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 I77.811 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for I77.811

For I77.811 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 I77.811 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

I77.811 is the ICD-10-CM diagnosis code for abdominal aortic ectasia. This condition involves an abnormal widening or ballooning of the abdominal aorta (the main blood vessel in the abdomen), but it is smaller than what would be classified as a true aneurysm. It represents a localized dilation of the aortic wall that requires monitoring to prevent progression. I77.811 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering diseases of arteries, arterioles and capillaries (i70-i79).

Under the older CMS-HCC V24 model, I77.811 maps to Vascular Disease (HCC 108) with a community, non-dual, aged base RAF weight of 0.288. 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.

Distinguish between ectasia (mild dilation) and aneurysm (larger dilation); ectasia codes are used for smaller dilations that don't meet aneurysm criteria. Because I77.811 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 I77.811 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Distinguish between ectasia (mild dilation) and aneurysm (larger dilation); ectasia codes are used for smaller dilations that don't meet aneurysm criteria
•Document the location (abdominal) and any associated symptoms or complications, as these may affect severity assessment and treatment decisions

Clinical Significance

Abdominal aortic ectasia represents mild dilation of the abdominal aorta below the aneurysm threshold (typically less than 3 cm). This sub-aneurysmal dilation requires surveillance as approximately 60% of patients progress to true aneurysm over time. It reflects ongoing vascular disease burden and the need for regular imaging follow-up, contributing to patient complexity in risk adjustment.

Documentation Requirements

✓Imaging confirmation with abdominal aortic diameter measurements (ultrasound, CT, or magnetic resonance imaging)
✓Documentation distinguishing ectasia from aneurysm based on size criteria
✓Surveillance plan including imaging follow-up intervals
✓Assessment of cardiovascular risk factors including smoking, hypertension, and family history
✓Current treatment plan including blood pressure management and smoking cessation if applicable

Commonly Confused Codes

•I71.4: Abdominal aortic aneurysm without rupture: use when dilation meets aneurysm threshold (3 cm or greater)
•I77.810: Thoracic aortic ectasia: different anatomic location
•I77.812: Thoracoabdominal aortic ectasia: use when both thoracic and abdominal segments are dilated
•I77.819: Aortic ectasia, unspecified site: less specific; use I77.811 when abdominal location is documented