2026 ICD-10-CM Diagnosis Code Q18.0Sinus, fistula and cyst of branchial cleft

ICD-10-CM Codes›Q00-Q99›Q10-Q18›Q18

ICD-10-CM Q18.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q18.0 is a billable ICD-10-CM diagnosis code for sinus, fistula and cyst of branchial cleft. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 154 through 156. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Congenital malformations of eye, ear, face, neck.

Code Identity

ICD-10-CM Code
Q18.0
Billable Status
Yes — Valid for Submission
Code Describes
Sinus, fistula and cyst of branchial cleft
Short Description
Sinus, fistula and cyst of branchial cleft
Same as the full description in the CMS dataset.
Parent Code
Q18
Other congenital malformations of face and neck

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ10-Q18Congenital malformations of eye, ear, face and neck
CategoryQ18Other congenital malformations of face and neck
This CodeQ18.0Sinus, fistula and cyst of branchial cleft

Present on Admission (POA)Billing

Q18.0 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.

  • Branchial cleft cyst
  • Branchial cleft external sinus
  • Branchial cleft internal sinus
  • Branchial cleft sinus
  • Branchial cleft sinus and fistula
  • Congenital anomaly of first branchial cleft
  • Congenital anomaly of fourth branchial cleft
  • Congenital anomaly of second branchial cleft
  • Congenital anomaly of third branchial cleft
  • First branchial cleft cyst
  • Fistula of branchial cleft
  • Fourth branchial cleft cyst
  • Second branchial cleft cyst
  • Third branchial cleft cyst

Tabular List NotesGuidance

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

Inclusion Terms

  • Branchial vestige

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.

    • Branchiogenic remnant(in neck)
    • Cleft(congenital)
      • branchial (persistent)
        • cyst
    • Cleft(congenital)
      • branchial (persistent)
        • cyst
          • fistula
    • Cleft(congenital)
      • branchial (persistent)
        • cyst
          • sinus
    • Cyst(colloid) (mucous) (simple) (retention)
      • branchial (cleft)
    • Cyst(colloid) (mucous) (simple) (retention)
      • branchiogenic
    • Cyst(colloid) (mucous) (simple) (retention)
      • cervical lateral
    • Fistula(cutaneous)
      • branchial (cleft)
    • Fistula(cutaneous)
      • branchiogenous
    • Fistula(cutaneous)
      • pharynx
        • branchial cleft (congenital)
    • Imperfect
      • closure (congenital)
        • branchial cleft NOS
          • cyst
    • Imperfect
      • closure (congenital)
        • branchial cleft NOS
          • fistula
    • Imperfect
      • closure (congenital)
        • branchial cleft NOS
          • sinus
    • Infection, infected, infective(opportunistic)
      • branchial cyst
    • Persistence, persistent(congenital)
      • branchial cleft NOS
        • cyst
    • Persistence, persistent(congenital)
      • branchial cleft NOS
        • fistula
    • Persistence, persistent(congenital)
      • branchial cleft NOS
        • sinus
    • Sinus
      • branchial cleft (internal) (external)
    • Vestige, vestigial
      • branchial

Clinical ClassificationClinical

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

CCSR MAL005
Congenital malformations of eye, ear, face, neck
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

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Convert Q18.0 to ICD-9-CMHistory

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

ICD-9-CM
744.41 Branch cleft sinus/fistu
Approximate The match is approximate rather than exact.
ICD-9-CM
744.42 Branchial cleft cyst
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 Q18.0Overview

Is Q18.0 (Other congenital malformations of face and neck) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report sinus, fistula and cyst of branchial cleft on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does Q18.0 group to?

When sinus, fistula and cyst of branchial cleft is the principal diagnosis on an inpatient stay, it groups to MS-DRG 154, 155, 156, with relative weights from 0.6911 to 1.5635 depending on complications. Higher weights mean higher Medicare reimbursement.

Is Q18.0 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 sinus, fistula and cyst of branchial cleft on inpatient claims.

What is the ICD-9 equivalent of Q18.0?

Under the General Equivalence Mappings, sinus, fistula and cyst of branchial cleft converts to ICD-9-CM 744.41 (branch cleft sinus/fistu) and 744.42 (branchial cleft cyst). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.