2026 ICD-10-CM Diagnosis Code Q33.1Accessory lobe of lung

ICD-10-CM Codes›Q00-Q99›Q30-Q34›Q33

ICD-10-CM Q33.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q33.1 is a billable ICD-10-CM diagnosis code for accessory lobe of lung. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 205 through 206. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Respiratory congenital malformations.

Code Identity

ICD-10-CM Code
Q33.1
Billable Status
Yes — Valid for Submission
Code Describes
Accessory lobe of lung
Short Description
Accessory lobe of lung
Same as the full description in the CMS dataset.
Parent Code
Q33
Congenital malformations of lung

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ30-Q34Congenital malformations of the respiratory system
CategoryQ33Congenital malformations of lung
This CodeQ33.1Accessory lobe of lung

Present on Admission (POA)Billing

Q33.1 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Accessory lobe of lung
  • Accessory lung
  • Accessory structure of lower respiratory tract
  • Azygos lobe of lung
  • Trilobed left lung

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Azygos lobe (fissured), lung

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Accessory(congenital)
      • lung (lobe)
    • Azygos
      • lobe (lung)

Clinical ClassificationClinical

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

CCSR MAL007
Respiratory congenital malformations
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

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Read the full article at MedlinePlus

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

Convert Q33.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
748.69 Lung anomaly NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Q33.1Overview

Is Q33.1 (Congenital malformations of lung) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report accessory lobe of lung on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does Q33.1 group to?

When accessory lobe of lung is the principal diagnosis on an inpatient stay, it groups to MS-DRG 205, 206, with relative weights from 0.9411 to 1.8310 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Q33.1 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for accessory lobe of lung on inpatient claims.

What is the ICD-9 equivalent of Q33.1?

Under the General Equivalence Mappings, accessory lobe of lung converts to ICD-9-CM 748.69 (lung anomaly NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.