2027 ICD-10-CM Diagnosis Code Q26.4Anomalous pulmonary venous connection, unspecified

ICD-10-CM Codes›Q00-Q99›Q20-Q28›Q26

ICD-10-CM Q26.4
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Q26.4 is a billable ICD-10-CM diagnosis code for anomalous pulmonary venous connection, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 306 through 307. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 8 closely related codes. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Cardiac and circulatory congenital anomalies.

Q26.4 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 191 for payment year 2027.

Code Identity

ICD-10-CM Code
Q26.4
Billable Status
Yes — Valid for Submission
Code Describes
Anomalous pulmonary venous connection, unspecified
Short Description
Anomalous pulmonary venous connection, unspecified
Same as the full description in the CMS dataset.
Parent Code
Q26
Congenital malformations of great veins

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ20-Q28Congenital malformations of the circulatory system
CategoryQ26Congenital malformations of great veins
This CodeQ26.4Anomalous pulmonary venous connection, unspecified

Present on Admission (POA)Billing

Q26.4 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Congenital malformations of the circulatory system (Q20-Q28).

Medicare Risk Adjustment (HCC)Billing

Q26.4 does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model, but it maps to payment categories in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
no payment category in the model that pays 100% of MA risk scores
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Part D (RxHCC)
RxHCC 191 — Ventricular Septal Defect and Major Congenital Heart Disorders
also risk-adjusts in the Part D prescription drug model (V08)

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.

  • Abnormal inferior vena caval connection
  • Anomalous pulmonary to systemic collateral vein
  • Anomalous pulmonary venous connection of mixed type
  • Anomalous pulmonary venous connection of mixed type with two pulmonary venous confluences
  • Anomalous pulmonary venous drainage
  • Anomalous pulmonary venous drainage to abdominal portion of inferior vena cava
  • Anomalous pulmonary venous drainage to coronary sinus
  • Anomalous pulmonary venous drainage to hepatic veins
  • Anomalous pulmonary venous drainage to right atrium
  • Anomalous pulmonary venous drainage to superior vena cava
  • Anomalous termination of right pulmonary vein
  • Congenital abnormality of hepatic vein
  • Congenital hypoplasia of pulmonary artery
  • Congenital hypoplasia of right side of chest
  • Congenital pulmonary vein confluence
  • Cor triatriatum with some pulmonary veins to proximal chamber draining to left atrium
  • Cor triatriatum with some pulmonary veins to proximal chamber draining to right atrium and others connecting directly to left atrium
  • Divided left atrium with some pulmonary veins to proximal chamber
  • Divided left atrium with some pulmonary veins to proximal chamber draining to left atrium and others connecting directly to left atrium
  • Divided left atrium with some pulmonary veins to proximal chamber draining to right atrium
  • Divided left atrium with some pulmonary veins to proximal chamber draining to right atrium and others connecting anomalously
  • Infracardiac location of anomalous pulmonary venous connection
  • Infracardiac location of anomalous pulmonary venous connection to hepatic vein
  • Infracardiac location of anomalous pulmonary venous connection to patent venous duct
  • Infracardiac location of anomalous pulmonary venous connection with two descending veins
  • Infracardiac location of anomalous pulmonary venous connections to inferior caval vein
  • Infracardiac location of anomalous pulmonary venous connections to portal system
  • Intracardiac location of anomalous pulmonary venous connection
  • Intracardiac location of anomalous pulmonary venous connection to coronary sinus
  • Intracardiac location of anomalous pulmonary venous connection to midline with isomeric atria
  • Intracardiac location of anomalous pulmonary venous connection to right atrium
  • Intracardiac location of anomalous pulmonary venous connections to bilateral isomeric atriums
  • Obstructed pulmonary venous connection
  • Obstructed pulmonary venous connection at coronary sinus orifice
  • Pulmonary vein atresia
  • Pulmonary venous confluence in direct proximity to left atrium
  • Pulmonary venous confluence in horizontal orientation
  • Pulmonary venous confluence in vertical orientation
  • Pulmonary venous confluence remote from left atrium
  • Scimitar syndrome
  • Scimitar syndrome with additional anomalous pulmonary venous connection
  • Supracardiac location of anomalous pulmonary venous connection
  • Supracardiac location of anomalous pulmonary venous connection to azygos vein
  • Supracardiac location of anomalous pulmonary venous connection to hemiazygos vein
  • Supracardiac location of anomalous pulmonary venous connection to left sided vertical vein
  • Supracardiac location of anomalous pulmonary venous connection to left superior caval vein
  • Supracardiac location of anomalous pulmonary venous connection to right sided vertical vein
  • Supracardiac location of anomalous pulmonary venous connection to right superior caval vein
  • Transposition of pulmonary veins

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Q26.4: its own notes plus those printed at Chapter 17. 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 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • inborn errors of metabolism (E70-E88)

Notes

General instructions on how these codes are used.

From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • Codes from this chapter are not for use on maternal records

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

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 MAL001
Cardiac and circulatory congenital anomalies
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Congenital Heart Defects

Congenital heart defects (CHDs) are problems with the structure of the heart. "Congenital" means that that the problems are present at birth. These defects happen when a fetus's heart doesn't develop normally during pregnancy. Congenital heart defects are the most common type of birth defect.

The full article covers:

  • What are congenital heart defects?
  • What causes congenital heart defects?
  • Who is more likely to have a baby with a congenital heart defect?
  • What are the symptoms of congenital heart defects?
  • What other problems do congenital heart defects cause?
  • How are congenital heart defects diagnosed?
  • What are the treatments for congenital heart defects?

Read the full article at MedlinePlus

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

Convert Q26.4 to ICD-9-CMHistory

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

ICD-9-CM
747.42 Part anom pulm ven conn
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About Q26.4Overview

What is the ICD-10 code for anomalous pulmonary venous connection, unspecified?

The ICD-10-CM code for anomalous pulmonary venous connection, unspecified is Q26.4 (sometimes written as Q264). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is Q26.4 (Congenital malformations of great veins) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report anomalous pulmonary venous connection, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does Q26.4 group to?

When anomalous pulmonary venous connection, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 306, 307, with relative weights from 0.9146 to 1.5457 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Q26.4 a CC or MCC?

CMS lists Q26.4 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 8 closely related codes in its exclusion list.

Is Q26.4 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 anomalous pulmonary venous connection, unspecified on inpatient claims. The code appears in the Congenital malformations of the circulatory system (Q20-Q28) range of the CMS exempt list.

Does Q26.4 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: Q26.4 maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the RxHCC Part D (V08) category 191 (Ventricular Septal Defect and Major Congenital Heart Disorders).