2027 ICD-10-CM Diagnosis Code I71.23Aneurysm of the descending thoracic aorta, without rupture

ICD-10-CM Codes›I00–I99›I70-I79›I71

ICD-10-CM I71.23
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

I71.23 is a billable ICD-10-CM diagnosis code for aneurysm of the descending thoracic aorta, without rupture. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 299 through 301. Coders also document this condition as aneurysm of descending thoracic aorta. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Aortic; peripheral; and visceral artery aneurysms.

I71.23 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 108 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 108, ESRD (V21) category 108, and ESRD (V24) category 108 for payment year 2027.

Code Identity

ICD-10-CM Code
I71.23
Billable Status
Yes — Valid for Submission
Code Describes
Aneurysm of the descending thoracic aorta, without rupture
Short Description
Aneurysm of the descending thoracic aorta, without rupture
Same as the full description in the CMS dataset.
Parent Code
I71.2
Thoracic aortic aneurysm, without rupture

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI70-I79Diseases of arteries, arterioles and capillaries
CategoryI71Aortic aneurysm and dissection
This CodeI71.23Aneurysm of the descending thoracic aorta, without rupture

Medicare Risk Adjustment (HCC)Billing

I71.23 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
Dropped in V28 see all codes that no longer risk-adjust
Prior Model (CMS-HCC V24)
HCC 108
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
Other CMS Models
PACE (CMS-HCC V22): HCC 108 · ESRD (V21): HCC 108 · ESRD (V24): HCC 108
ESRD V21 weights: 0.065 dialysis, 0.086–0.271 functioning graft · ESRD V24 weights: 0.073 dialysis, 0.074–0.287 functioning graft
Part D (RxHCC)
Not mapped
I71.23 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Aneurysm of descending thoracic aorta

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I71.23: its own notes plus those printed at I71 and Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 9 (I00-I99) Diseases of the circulatory system applies to 1,433 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)
  • transient cerebral ischemic attacks and related syndromes (G45.-)

Code First

The underlying condition named in the note is sequenced before this code.

From I71 Aortic aneurysm and dissection applies to 31 codes
  • if applicable:
  • syphilitic aortic aneurysm (A52.01)
  • traumatic aortic aneurysm (S25.09, S35.09)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name I71.23, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming I71.23: they are not reported together with it, unless the two conditions are unrelated.

  • I77.81 Aortic ectasia
    aortic aneurysm and dissection (I71.-) names I71.-, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming I71.23: its condition is not part of those codes, and both may be reported when the patient has both.

  • I72 Other aneurysm
    aneurysm (of) aorta (I71.-) names I71.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR CIR029
Aortic; peripheral; and visceral artery aneurysms
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Aortic Aneurysm, Thoracic

    an abnormal balloon- or sac-like dilatation in the wall of the thoracic aorta. this proximal descending portion of aorta gives rise to the visceral and the parietal branches above the aortic hiatus at the diaphragm.

Patient EducationClinical

Aortic Aneurysm

An aneurysm is a bulge or "ballooning" in the wall of an artery. Arteries are blood vessels that carry oxygen-rich blood from the heart to other parts of the body. If an aneurysm grows large, it can burst and cause dangerous bleeding or even death.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code History & ChangesHistory

Replacement I71.23 replaces the following previously assigned code(s):

  • I71.2 - Thoracic aortic aneurysm, without rupture
FY 2023AddedAdded to the ICD-10-CM code setEffective October 1, 2022.
FY 2024–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About I71.23Overview

What is the ICD-10 code for aneurysm of the descending thoracic aorta, without rupture?

The ICD-10-CM code for aneurysm of the descending thoracic aorta, without rupture is I71.23 (sometimes written as I7123). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is I71.23 (Thoracic aortic aneurysm, without rupture) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report aneurysm of the descending thoracic aorta, without rupture on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does I71.23 group to?

When aneurysm of the descending thoracic aorta, without rupture is the principal diagnosis on an inpatient stay, it groups to MS-DRG 301, 300, 299, with relative weights from 0.7132 to 1.5840 depending on complications. Higher weights mean higher Medicare reimbursement.

What is coded first with I71.23?

The Code First note at I71, which applies to I71.23, reads: , if applicable: syphilitic aortic aneurysm (A52.01); traumatic aortic aneurysm (S25.09, S35.09). When one of these applies, it is sequenced before I71.23.

Does I71.23 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. I71.23 mapped to HCC 108 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 108 (Vascular Disease), ESRD (V21) category 108 (Vascular Disease), and ESRD (V24) category 108 (Vascular Disease).