Crystal's MCW Coder Hub🧬CPT Code 31256: Nasal/Sinus Endoscopy, Surgical, with Maxillary Antrostomy
📋 Code Information
| Field | Value |
|---|---|
| CPT Code | 31256 |
| Descriptor | Nasal/sinus endoscopy, surgical, with maxillary antrostomy |
| Section | Surgical Procedures on the Accessory Sinuses (31231-31298) |
| Approach | Endoscopic |
| Global Period | 90 days |
| Effective Date | 1994-01-01 |
| Last Updated | 2026-01-01 (no change from 2025) |
📖 Clinical Description
CPT Code 31256 describes a surgical endoscopic procedure to create or enlarge an opening (antrostomy) in the maxillary sinus. The surgeon inserts an endoscope into the nasal cavity, gains access to the maxillary sinus through a cut in the uncinate process, and opens the maxillary sinus ostium to improve drainage and ventilation.[4][8]
Procedure Steps[4][8]
- Endoscope Insertion: The surgeon inserts a nasal endoscope to visualize the nasal cavity and sinus anatomy.
- Access to Maxillary Sinus: The uncinate process is incised to expose the natural ostium of the maxillary sinus.
- Antrostomy Creation: The sinus opening is enlarged using surgical instruments such as through-cutting forceps, microdebriders, or balloon dilation devices.
- Inspection: The maxillary sinus may be inspected through the newly created opening to assess for pathology.
- Closure: There are typically no external incisions; the procedure is performed entirely through the nostrils.
Indications
- Chronic maxillary sinusitis refractory to medical management[5]
- Recurrent acute sinusitis
- Sinus ostial obstruction
- Access for biopsy or culture of sinus contents
- Part of comprehensive functional endoscopic sinus surgery (FESS)[5]
🔍 Includes and Inclusions
- Surgical Endoscopy: Includes diagnostic endoscopy of the nasal cavity and sinuses (do not report 31231 separately)[6]
- Maxillary Antrostomy: Creation or enlargement of the maxillary sinus ostium
- Unilateral Procedure: Code describes one side (use modifier 50 for bilateral)[8]
- Instrumentation: Use of endoscopic instruments to perform the antrostomy
🚫 Excludes and Differentiating Codes
Do Not Report 31256 With
| Code | Description | Rationale |
|---|---|---|
| 31231 | Diagnostic nasal endoscopy | Bundled into surgical endoscopy[6] |
| 31267 | Maxillary antrostomy with tissue removal | More comprehensive; 31256 is component[6][9] |
| 31233 | Nasal/sinus endoscopy, diagnostic, with maxillary sinusoscopy | Diagnostic version |
| 31237 | Nasal/sinus endoscopy with biopsy or polypectomy | Different procedure |
Code When Tissue Is Removed
31267 (with removal of tissue from maxillary sinus) should be used instead of 31256 when the surgeon removes polyps, cysts, mucopus, or other tissue from the maxillary sinus.[6][9]
Related Codes
| Code | Description |
|---|---|
| 31254 | Partial ethmoidectomy |
| 31255 | Total ethmoidectomy |
| 31276 | Frontal sinus exploration |
| 31287 | Sphenoidotomy |
| 31295 | Balloon dilation of maxillary sinus ostium |
📊 Code Tree and Hierarchy
flowchart TD A["31231-31298 Endoscopy Procedures on the Accessory Sinuses"] --> B["Diagnostic Endoscopy"] B --> C["31231 Nasal/sinus endoscopy, diagnostic"] B --> D["31233 Maxillary sinusoscopy"] B --> E["31235 Sphenoid sinusoscopy"] A --> F["Surgical Endoscopy"] F --> G["Maxillary Sinus Procedures"] G --> H["31256 Maxillary antrostomy<br>WITHOUT tissue removal"] G --> I["31267 Maxillary antrostomy<br>WITH tissue removal"] F --> J["Ethmoid Sinus Procedures"] J --> K["31254 Partial ethmoidectomy"] J --> L["31255 Total ethmoidectomy"] F --> M["Sphenoid Sinus Procedures"] M --> N["31287 Sphenoidotomy"] M --> O["31288 Sphenoidotomy with tissue removal"] F --> P["Frontal Sinus Procedures"] P --> Q["31276 Frontal sinus exploration"]
🔄 Modifiers and Billing Nuances[8]
| Modifier | Description | Application to 31256 |
|---|---|---|
| -50 | Bilateral Procedure | Use when procedure is performed on both right and left maxillary sinuses during same session |
| -51 | Multiple Procedures | Apply when multiple sinus procedures are performed (e.g., ethmoidectomy + maxillary antrostomy) |
| -59 | Distinct Procedural Service | Use to indicate procedure is distinct from other services performed on same day |
| -22 | Increased Procedural Services | Use when work required is substantially greater than typical (requires documentation) |
| -76 | Repeat Procedure by Same Physician | Applied when same procedure is repeated on same day |
| -77 | Repeat Procedure by Another Physician | Used when procedure is repeated by different physician on same day |
| -79 | Unrelated Procedure | Use when performed during postoperative period of another, unrelated surgery |
| -62 | Two Surgeons | Used when two surgeons work as primary surgeons performing distinct parts of procedure[3] |
👨⚕️ Assistant Surgeon (Modifier 80) Payability
Assistant Surgeon Information
- Assistant Surgeon Status: Generally not payable as assistant surgeon for routine cases
- Medicare Payment Indicator: Check MPFSDB “Asst Surg” indicator for current status
- Documentation Requirements: If assistant is medically necessary, documentation must support:
- Patient factors (morbid obesity, complex anatomy)
- Unusual circumstances (excessive bleeding, extensive disease)
- Need for two surgeons performing distinct procedures[3]
Billing Scenarios Involving Assistants[3]
If two surgeons of different specialties perform distinct procedures during the same operative session:
- Physician A (e.g., Oral Surgeon) performs primary procedure (e.g., Caldwell-Luc)
- Physician B (e.g., ENT) performs nasal antrostomy (31256)
Both physicians should:
- Bill their respective procedures as primary surgeons
- Each dictate their own operative report documenting their distinct procedure
- Do not use assistant modifiers if performing distinct, separately identifiable procedures[3]
Co-Surgery (Modifier 62)[3]
If both surgeons work together as co-surgeons performing the same procedure:
- Both report the same CPT code with modifier 62
- Reimbursement is typically 125% of the fee schedule amount, split equally
💰 Work RVU (wRVU) and Reimbursement
Work RVU Information
The Work Relative Value Units (wRVU) for 31256 are updated annually by CMS. For current values:
- 2026 Reference: Consult the most recent CMS Physician Fee Schedule (PFS) Final Rule or the AMA RBRVS DataManager[7]
- Reimbursement Factors: Final payment determined by:
- Total RVUs (Work + Practice Expense + Malpractice)
- Geographic Practice Cost Index (GPCI) for your area
- National conversion factor ($33.40 for 2026 non-APM participants)[7]
Medicare Administrative Contractor (MAC) Considerations[8]
Reimbursement may vary based on:
- Local Coverage Determinations (LCDs) in your region
- Specific MAC policies and documentation requirements
- Medical necessity criteria for sinus surgery
📋 Documentation Requirements
To support billing of 31256, the operative report should clearly document:[1][6][9]
- Preoperative Diagnosis: Specific sinus pathology requiring antrostomy
- Procedure Performed: “Maxillary antrostomy” or “maxillary sinus ostium enlargement”
- Laterality: Right, left, or bilateral
- Findings: Description of sinus mucosa, presence of pus, polyps, or other pathology
- Tissue Removal: Explicitly state if no tissue was removed from the maxillary sinus
- Extent of Procedure: Whether other sinuses were addressed
- Technique: Instruments used (forceps, microdebrider, balloon)
📊 ICD-10 Crosswalk and HCC Information
Common ICD-10 Diagnoses for 31256[5]
| ICD-10 Code | Description | HCC Applicability |
|---|---|---|
| J32.0 | Chronic maxillary sinusitis | No (0) |
| J32.9 | Chronic sinusitis, unspecified | No (0) |
| J33.8 | Other polyp of sinus | No (0) |
| J33.9 | Nasal polyp, unspecified | No (0) |
| J34.89 | Other specified disorders of nose and nasal sinuses | No (0) |
| J01.00 | Acute maxillary sinusitis, unspecified | No (0) |
| C31.0 | Malignant neoplasm of maxillary sinus | Yes (HCC 8 or 10) |
| D14.0 | Benign neoplasm of middle ear, nasal cavity and accessory sinuses | No (0) |
HCC Note
Most sinusitis and polyp diagnoses are not hierarchical condition categories (HCCs) that affect risk adjustment payments. Malignant neoplasms of the sinus (C31.0) do map to HCCs and impact risk scores.
🏥 MS-DRG Assignment
When performed in an inpatient setting (rare; typically outpatient), 31256 may map to:
| MS-DRG | Description |
|---|---|
| 129 | Major head and neck procedures with CC/MCC |
| 130 | Major head and neck procedures without CC/MCC |
| 152 | Otitis media and URI with MCC |
| 153 | Otitis media and URI without MCC |
Note: 31256 is typically performed in outpatient/ambulatory surgical center (ASC) settings and is not usually assigned to inpatient MS-DRGs.
📝 Coding Examples and Scenarios
Example 1: Simple Maxillary Antrostomy
Scenario: A 45-year-old with chronic maxillary sinusitis refractory to antibiotics undergoes endoscopic sinus surgery. The surgeon performs a right maxillary antrostomy, enlarging the natural ostium. No polyps or tissue are removed from the sinus. Coding:
- 31256 - -RT (Nasal/sinus endoscopy, surgical, with maxillary antrostomy, right side)
- J32.0 (Chronic maxillary sinusitis)
Example 2: Bilateral Maxillary Antrostomy
Scenario: A 52-year-old with bilateral chronic maxillary sinusitis undergoes endoscopic sinus surgery. The surgeon performs maxillary antrostomy on both sides. No tissue is removed from either sinus. Coding:
- 31256 - -50 (Nasal/sinus endoscopy, surgical, with maxillary antrostomy, bilateral)
- J32.9 (Chronic sinusitis, unspecified)
Example 3: Multiple Sinus Procedures
Scenario: A patient undergoes endoscopic sinus surgery including bilateral total ethmoidectomies and bilateral maxillary antrostomies without tissue removal. Coding:
- 31255 - -50 (Total ethmoidectomy, bilateral)
- 31256 - -51 - -50 (Maxillary antrostomy, bilateral, multiple procedures)
- Note: Modifier -51 indicates multiple procedures; Medicare carriers apply multiple procedure payment reduction automatically[6]
Example 4: Maxillary Antrostomy WITH Tissue Removal
Scenario: A patient undergoes endoscopic sinus surgery. The surgeon performs bilateral maxillary antrostomies and removes polyps from both maxillary sinuses. Coding:
- Correct: 31267 - 50 (Maxillary antrostomy with tissue removal, bilateral)
- Incorrect: 31256 - 50 + 31267 - 50
- Rationale: 31256 is a component of 31267; when tissue is removed, report only 31267[6][9]
Example 5: Two Surgeons, Different Procedures
Scenario: Oral surgeon performs Caldwell-Luc procedure. ENT performs endoscopic maxillary antrostomy during same operative session. Coding:
- Oral Surgeon: Appropriate Caldwell-Luc code (e.g., 21345) as primary surgeon
- ENT: 31256 as primary surgeon (no modifier)[3]
- Rationale: Each physician bills their distinct procedure as primary surgeon with own op note
Example 6: Co-Surgery Scenario
Scenario: Two ENT surgeons work together as co-surgeons to perform a complex bilateral maxillary antrostomy due to difficult anatomy and extensive disease. Coding:
- Both surgeons: 31256 - -62 - -50
- Rationale: Modifier 62 indicates co-surgery; both report same code with modifier
Example 7: Incorrect Reporting of Diagnostic Endoscopy
Scenario: Surgeon performs diagnostic nasal endoscopy followed by maxillary antrostomy. Coder reports 31231 and 31256. Coding:
- Correct: 31256 only
- Incorrect: 31231 + 31256
- Rationale: Surgical endoscopy includes diagnostic endoscopy; do not report separately[6]
⚠️ Important Coding Notes
31256 vs. 31267 Distinction[6][9]
The critical factor in choosing between 31256 and 31267 is whether tissue was removed from the maxillary sinus:
| Factor | 31256 | 31267 |
|---|---|---|
| Antrostomy | ✓ Yes | ✓ Yes |
| Tissue Removal | ✗ No | ✓ Yes |
| Polypectomy | ✗ No | ✓ Yes |
| Mucosal Stripping | ✗ No | ✓ Yes |
| Cyst Removal | ✗ No | ✓ Yes |
NCCI Edits[6][9]
- 31256 is a component of 31267 and should not be reported together
- Surgical endoscopy codes bundle the associated diagnostic endoscopy (31231)
- Multiple sinus procedures may be reported together with modifier -51
Bilateral Surgery[6][8]
- Use modifier -50 for bilateral procedures
- Medicare typically pays 150% of the unilateral fee for bilateral procedures (75% per side)
References
1 Haugen Consulting Group. “Webinar Q&A: Procedure Coding for Sinus Surgery.” (2025) 2 Bristol Healthcare Services. “CPT® 2026 Overhaul: Thoracic Endovascular Aortic Repair Coding Changes.” (2026) 3 AAPC Forum. “Assistant Surgery billing as Primary surgeon.” (2012) 4 AAPC. “CPT® Code 31256 - Endoscopy Procedures on the Accessory Sinuses.” (2026) 5 NIH/NCBI. “Table 1. Diagnosis and Procedure Codes for Sinus Surgery.” (2024) 6 AAPC. “You Be the Coder: Septoplasty With FESS, Turbinoplasties.” (2008) 7 ISASS. “2026 CPT® Code Updates for Spine Surgery.” (2026) 8 MD Clarity. “CPT Code 31256: What It Is, Modifiers, Reimbursement.” (2026) 9 AAPC. “Reader Questions: Know Criteria for 31256 to 31267 Conversion.” (2021) 10 MedLearn Publishing. “Peripheral & Cardiology Coder - 2026 Edition.” (2026)