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ICD-10-PCS 2027 procedure code

099C0ZZDrainage of Left Mastoid Sinus, Open Approach

✓ Valid for 2027O.R. procedure

Code unchanged since ICD-10-PCS took effect on October 1, 2015. Source: official FY2027 ICD-10-PCS release from CMS. Page updated September 29, 2026. About our data

About 099C0ZZ

099C0ZZ is the ICD-10-PCS code for a drainage procedure on the left mastoid sinus using an open approach. In ICD-10-PCS, drainage means taking or letting out fluids and/or gases from a body part.

In plain terms, this corresponds to incision of mastoid and incision of petrous pyramid air cells, the ICD-9-CM procedure titles it maps to (20.21 and 20.22).

For a different body part, codes include 09900ZZ (right external ear), 09910ZZ (left external ear), 09930ZZ (right external auditory canal), 09940ZZ (left external auditory canal), 09950ZZ (right middle ear), 09960ZZ (left middle ear) and 22 more.

The same procedure with a different approach is coded 099C3ZZ (percutaneous), 099C4ZZ (percutaneous endoscopic), 099C7ZZ (via natural or artificial opening) and 099C8ZZ (via natural or artificial opening endoscopic).

With a different device, use 099C00Z (drainage device).

It is an operating-room procedure in the MS-DRG logic for DRG 135 (Sinus and Mastoid Procedures with CC/MCC) and DRG 136 (Sinus and Mastoid Procedures without CC/MCC), under the surgical category “Sinus and Mastoid Procedures”.

It has been valid since ICD-10-PCS took effect on October 1, 2015.

What each character means

1. Section
0Medical and Surgical
2. Body System
9Ear, Nose, Sinus
3. Operation
9Drainage

Taking or letting out fluids and/or gases from a body part

The qualifier DIAGNOSTIC is used to identify drainage procedures that are biopsies

Includes: Thoracentesis, incision and drainage

4. Body Part
CMastoid Sinus, Left

Includes: Mastoid air cells

5. Approach
0Open

Cutting through the skin or mucous membrane and any other body layers necessary to expose the site of the procedure

6. Device
ZNo Device
7. Qualifier
ZNo Qualifier

Other versions of this procedure

Different device

Different qualifier

MS-DRG v44.0 grouping

All DRGs →

Surgical MS-DRGs this procedure can group to, depending on the principal diagnosis's MDC.

MDC 03 · Diseases and Disorders of the Ear, Nose, Mouth and Throat · Sinus and Mastoid Procedures

ICD-9-CM equivalent

Converter →
  • 20.21Incision of mastoidapproximate
  • 20.22Incision of petrous pyramid air cellsapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about 099C0ZZ

Is 099C0ZZ a valid ICD-10-PCS code for 2027?

Yes. 099C0ZZ is valid for inpatient procedures from October 1, 2026 through September 30, 2027.

Is 099C0ZZ an O.R. procedure?

Yes. 099C0ZZ is an O.R. procedure in MS-DRG v44.0.

What DRG does 099C0ZZ group to?

Depending on the principal diagnosis, 099C0ZZ can group to MS-DRG 135 and MS-DRG 136.

What is the ICD-9 procedure code for 099C0ZZ?

The CMS GEMs map 099C0ZZ to ICD-9-CM 20.21 (Incision of mastoid) and 20.22 (Incision of petrous pyramid air cells).