2026 ICD-10-CM Diagnosis Code Q42.1Congenital absence, atresia and stenosis of rectum without fistula

ICD-10-CM Codes›Q00-Q99›Q38-Q45›Q42

ICD-10-CM Q42.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q42.1 is a billable ICD-10-CM diagnosis code for congenital absence, atresia and stenosis of rectum without fistula. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 393 through 395. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Digestive congenital anomalies.

Code Identity

ICD-10-CM Code
Q42.1
Billable Status
Yes — Valid for Submission
Code Describes
Congenital absence, atresia and stenosis of rectum without fistula
Short Description
Congen absence, atresia and stenosis of rectum w/o fistula
Parent Code
Q42
Congenital absence, atresia and stenosis of large intestine

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ38-Q45Other congenital malformations of the digestive system
CategoryQ42Congenital absence, atresia and stenosis of large intestine
This CodeQ42.1Congenital absence, atresia and stenosis of rectum without fistula

Present on Admission (POA)Billing

Q42.1 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.

  • Anorectal agenesis
  • Anorectal stricture
  • Atresia and stenosis of large intestine, rectum and anal canal
  • Congenital absence of large intestine
  • Congenital absence of rectum
  • Congenital atresia of large intestine
  • Congenital atresia of rectum
  • Congenital rectal stenosis
  • Congenital stenosis of large intestine
  • Congenital stricture of rectum
  • Stenosis of rectum
  • Stricture of rectum

Tabular List NotesGuidance

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

Inclusion Terms

  • Imperforate rectum

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.

    • Absence(of) (organ or part) (complete or partial)
      • rectum (congenital)
    • Agenesis
      • rectum
    • Atresia, atretic
      • rectum
    • Hypoplasia, hypoplastic
      • rectum
    • Imperforate(congenital)
      • rectum
    • Impervious(congenital)
      • rectum
    • Stricture
      • rectum (sphincter)
        • congenital

Clinical ClassificationClinical

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

CCSR MAL002
Digestive congenital anomalies
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Birth Defects

A birth defect is a problem that happens while a baby is developing in the mother's body. Most birth defects happen during the first 3 months of pregnancy. One out of every 33 babies in the United States is born with a birth defect.

The full article covers:

  • What are birth defects?
  • What causes birth defects?
  • Who is at risk of having a baby with birth defects?
  • How are birth defects diagnosed?
  • What are the treatments for birth defects?
  • Can birth defects be prevented?

Read the full article at MedlinePlus

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

Convert Q42.1 to ICD-9-CMHistory

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

ICD-9-CM
751.2 Atresia large intestine
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 Q42.1Overview

Is Q42.1 (Congenital absence, atresia and stenosis of large intestine) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report congenital absence, atresia and stenosis of rectum without fistula on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does Q42.1 group to?

When congenital absence, atresia and stenosis of rectum without fistula is the principal diagnosis on an inpatient stay, it groups to MS-DRG 393, 394, 395, with relative weights from 0.6490 to 1.5993 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Q42.1 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 congenital absence, atresia and stenosis of rectum without fistula on inpatient claims.

What is the ICD-9 equivalent of Q42.1?

Under the General Equivalence Mappings, congenital absence, atresia and stenosis of rectum without fistula converts to ICD-9-CM 751.2 (atresia large intestine). 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.