Skip to main content

I71.20 ICD-10-CM Code: Thoracic aortic aneurysm, without rupture, unspecified

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
3 code-first instructions
Risk adjustment
CMS-HCC V22 category 108

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 299 — PERIPHERAL VASCULAR DISORDERS WITH MCC (MDC 05)
  • MS-DRG 300 — PERIPHERAL VASCULAR DISORDERS WITH CC (MDC 05)
  • MS-DRG 301 — PERIPHERAL VASCULAR DISORDERS WITHOUT CC/MCC (MDC 05)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for I71.20 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on I71.20 itself; “inherited from” names the category or block whose note applies here.

Code First

Underlying conditions that must be sequenced before this code.

  • Code first, if applicable:
  • syphilitic aortic aneurysm (A52.01)
  • traumatic aortic aneurysm (S25.09, S35.09)

Source: inherited from I71

Coder workflow for I71.20

MedCoder structured workflow — derived from this code’s own official record

Before you code I71.20

  1. Unspecified does not mean incorrect. When the record gives no greater specificity, I71.20 may be the appropriate code. Check the record for detail that supports a more specific sibling — in this subcategory the siblings differ by the presence or absence of the associated condition. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18).

    ReviewI71.21, I71.22, I71.23

    See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

Choose the right path

  1. Does the record document the detail a more specific sibling code needs?
    Yes → Review the specific siblings in this subcategory.
    No → Continue — I71.20 is appropriate when the documentation goes no further.

    ReviewI71.21, I71.22, I71.23

  2. Is the underlying (etiologic) condition the Code First note names documented?
    Yes → Sequence the underlying condition first, then I71.20.
    No → Continue; do not add an underlying condition the record does not document.

    ReviewA52.01, S25.09, S35.09

Consider I71.20. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The associated condition or complication
Whether the associated condition the title names is documented; the “with” convention presumes some links, and a provider statement that the conditions are unrelated defeats it (Guidelines I.A.15).
The underlying (etiologic) condition
Named in the Code First note; sequenced before this code when documented (Guidelines I.A.13).
Any detail beyond this code’s title
What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

  • Code First — sequencing check(3 notes)

    Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before I71.20. Do not add an underlying condition the record does not document.

    ReviewA52.01, S25.09, S35.09

    See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: The provider documents the condition in the terms of this code’s title and records no further detail.

Coding question: Is a more specific sibling code supportable?

Path: Review the specific siblings in this subcategory and what each requires the record to state.

Reason: A more specific code needs documentation of the distinguishing element; without it the unspecified code is appropriate, and a provider query is the route to specificity (Guidelines I.A.9.b, I.B.18).

ReviewI71.21, I71.22, I71.23

Documentation: The underlying condition the Code First note names is documented alongside this condition.

Coding question: How are the two sequenced?

Path: Review the Code First note.

Reason: The underlying condition is sequenced first and the manifestation follows (Guidelines I.A.13).

ReviewA52.01, S25.09, S35.09

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Thoracic aortic aneurysm, without rupture, unspecified is a billable ICD-10-CM diagnosis code (I71.20).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (5)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name I71.20 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: I77.81 — Aortic ectasia (via I71.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Excludes2 note: I72 — Other aneurysm (via I71.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 3 MS-DRGs: DRG 299 (MDC 05), DRG 300 (MDC 05), DRG 301 (MDC 05).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):CIR029 — Aortic; peripheral; and visceral artery aneurysms (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Aortic; peripheral; and visceral artery aneurysms).

A52.01 — Syphilitic aneurysm of aorta, I71.1 — Thoracic aortic aneurysm, ruptured, I71.10 — Thoracic aortic aneurysm, ruptured, unspecified, I71.11 — Aneurysm of the ascending aorta, ruptured, I71.12 — Aneurysm of the aortic arch, ruptured, I71.13 — Aneurysm of the descending thoracic aorta, ruptured, I71.2 — Thoracic aortic aneurysm, without rupture, I71.21 — Aneurysm of the ascending aorta, without rupture, I71.22 — Aneurysm of the aortic arch, without rupture, I71.23 — Aneurysm of the descending thoracic aorta, without rupture, I71.3 — Abdominal aortic aneurysm, ruptured, I71.30 — Abdominal aortic aneurysm, ruptured, unspecified, I71.31 — Pararenal abdominal aortic aneurysm, ruptured, I71.32 — Juxtarenal abdominal aortic aneurysm, ruptured, I71.33 — Infrarenal abdominal aortic aneurysm, ruptured, I71.4 — Abdominal aortic aneurysm, without rupture, I71.40 — Abdominal aortic aneurysm, without rupture, unspecified, I71.41 — Pararenal abdominal aortic aneurysm, without rupture, I71.42 — Juxtarenal abdominal aortic aneurysm, without rupture, I71.43 — Infrarenal abdominal aortic aneurysm, without rupture, +20 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Aneurysm”; these codes share that main term but sit in a different category of the Tabular List.

I33.0 — Acute and subacute infective endocarditis (mycotic, endocardial), I34.89 — Other nonrheumatic mitral valve disorders (mitral), I35.8 — Other nonrheumatic aortic valve disorders (aorta, aortic, valve), I60.0 — Nontraumatic subarachnoid hemorrhage from carotid siphon and bifurcation (carotid artery, ruptured into brain), I60.6 — Nontraumatic subarachnoid hemorrhage from other intracranial arteries (circle of Willis, ruptured), I60.7 — Nontraumatic subarachnoid hemorrhage from unspecified intracranial artery (berry, ruptured), I60.8 — Other nontraumatic subarachnoid hemorrhage (brain, meninges, ruptured), I61.5 — Nontraumatic intracerebral hemorrhage, intraventricular (arteriovenous, brain, ruptured, intraventricular), I61.8 — Other nontraumatic intracerebral hemorrhage (arteriovenous, brain, ruptured, intracerebral), I67.1 — Cerebral aneurysm, nonruptured (brain), I72.0 — Aneurysm of carotid artery (neck), I72.1 — Aneurysm of artery of upper extremity (ulnar), I72.2 — Aneurysm of renal artery (renal), I72.3 — Aneurysm of iliac artery (iliac), I72.4 — Aneurysm of artery of lower extremity (femoral), I72.5 — Aneurysm of other precerebral arteries (basilar), I72.6 — Aneurysm of vertebral artery (vertebral artery), I72.8 — Aneurysm of other specified arteries (celiac), I72.9 — Aneurysm of unspecified site, I77.0 — Arteriovenous fistula, acquired (arteriovenous, acquired), +24 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Lipid Panel, Prothrombin Time Test and INR (PT/INR)

Contextual Map

Every relationship of I71.20 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run I71.20 with these 2 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

  • I77.81 — Aortic ectasia[Excludes1](via I71.-): “aortic aneurysm and dissection (I71.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Referenced by Excludes2 notes

  • I72 — Other aneurysm[Excludes2](via I71.-): “aneurysm (of) aorta (I71.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 05 — Diseases and Disorders of the Circulatory System[MDC crossing]: “Diseases and Disorders of the Circulatory System — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 17,209 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

  • Aneurysm (anastomotic) (artery) (cirsoid) (diffuse) (false) (fusiform) (multiple) (saccular), aorta, aortic (nonsyphilitic), thoracic[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Aneurysm (anastomotic) (artery) (cirsoid) (diffuse) (false) (fusiform) (multiple) (saccular), aorta, aortic (nonsyphilitic), thorax, thoracic[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Aneurysm (anastomotic) (artery) (cirsoid) (diffuse) (false) (fusiform) (multiple) (saccular), intrathoracic (nonsyphilitic)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Disease, diseased, Hodgson's[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Hodgson's[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (39)

Change history

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "I71.20 — Thoracic aortic aneurysm, without rupture, unspecified." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/i71.20-thoracic-aortic-aneurysm-without-rupture-unspecified

Change history

  • FY2023 — October 1, 2022
    Added to the code set
    Thoracic aortic aneurysm, without rupture, unspecified
    FY2023 changes

Nearest Codes in This Family

Official ICD-10-CM classifications closest to I71.20 in its code family, with their registry titles.

View all codes in the I71 family