CPT® Code 31231

Last Updated: February 2026 | Verified for 2026 AMA, CPT & CMS Guidelines

Quick Reference: CPT 31231 (Diagnostic Nasal Endoscopy)

• What CPT 31231 means: Diagnostic nasal endoscopy, unilateral or bilateral, performed to evaluate the nasal cavity and sinonasal anatomy beyond the limits of anterior rhinoscopy. It is a diagnostic scope service (not a therapeutic sinus surgery code) and is commonly used for chronic sinonasal symptoms, suspected polyps/masses, epistaxis evaluation, CSF rhinorrhea workup, and surveillance of known disease.
• “Unilateral or bilateral” is built into the code: CPT 31231 is reported once per session whether one or both nasal cavities are examined. Do not append modifier 50 or report RT/LT for Medicare-style laterality; billing two units for “both sides” is incorrect. Document which side(s) were examined clinically, but report the code once.
• Bundling is the biggest denial driver: CPT 31231 is a diagnostic “separate procedure” conceptually and is frequently not separately payable when performed with more extensive nasal/sinus endoscopic procedures on the same side/session. NCCI policy and ENT specialty guidance emphasize that diagnostic scoping is often considered integral to related therapeutic procedures.
• Scopes on the same DOS require careful selection: When nasal endoscopy is performed on the same date as other endoscopic ENT procedures (e.g., laryngoscopy), code selection must follow NCCI edits and payer logic. In some combinations, a distinct-procedure modifier may be appropriate only when the services are truly separate and clearly documented; in other combinations, separate reporting is not allowed.
• Modifier 25 is common and commonly audited: If a significant, separately identifiable E/M service is performed on the same date as nasal endoscopy, append modifier 25 to the E/M code and document a distinct evaluation beyond the inherent pre-scope assessment. Do not reflexively bill E/M + 31231 without clear, separate medical decision-making.
• Documentation must make the service auditable: Document the indication, scope type (rigid/flexible), structures examined, key findings, and any clinically relevant patient response/tolerance. ENT specialty indicators emphasize documenting both why the endoscopy was needed and what was found. Missing indication or missing findings is a frequent payer recoupment trigger. CPT 31231 (diagnostic nasal endoscopy) is one of the most common otolaryngology office procedures and also one of the most denial-prone when billed alongside other nasal/sinus procedures or additional endoscopies on the same date of service. The payment and audit risk usually comes from a small set of repeatable errors: (1) billing 31231 as “bilateral” with modifier 50 or multiple units, (2) billing 31231 in situations where payers consider it bundled into a more comprehensive endoscopic procedure, (3) using distinct-procedure modifiers (especially 59) without documentation that the scopes were truly separate, and (4) reporting an E/M visit that is not separately supported when the visit work is primarily pre-procedure assessment. This 2026 guide is designed to be payer-realistic: it focuses on how CMS/NCCI logic and ENT specialty guidance are operationalized in claims and audits.

1. Clinical Definition, Procedure Scope, and When 31231 Is Medically Necessary

CPT 31231 describes a diagnostic nasal endoscopy performed with an endoscope to evaluate the nasal cavity and related sinonasal anatomy. Clinically, diagnostic nasal endoscopy is used when anterior rhinoscopy is insufficient to characterize symptoms, abnormal findings, or disease extent. ENT specialty guidance describes diagnostic nasal endoscopy as an office-based evaluation tool that can visualize structures such as the septum, inferior and middle turbinates, middle meatus, sphenoethmoid recess, and nasopharyngeal region depending on technique and clinical need.

The American Rhinologic Society’s position statement for CPT 31231 frames diagnostic nasal endoscopy as a key diagnostic procedure for rhinologic disease evaluation, including chronic rhinosinusitis and related inflammatory disorders.

1.1 What 31231 includes (coding-relevant scope)

• Diagnostic visualization of the nasal cavity using an endoscope (rigid or flexible; technique is clinical, the CPT code is the diagnostic service).
• Unilateral or bilateral evaluation in the same session: the CPT descriptor includes both possibilities, which is why separate “bilateral” coding is generally not appropriate.
• Findings documentation sufficient to support the indication and medical necessity for the diagnostic evaluation (see Section 5).

1.2 Common, defensible indications (examples)

Indications vary by payer and clinical context, but the most defensible use cases share a common theme: the scope is needed to answer a clinically important question that cannot be answered by history and anterior rhinoscopy alone. ENT clinical indicator guidance supports nasal endoscopy as an evaluation method for a range of rhinologic complaints and disease surveillance.

• Chronic rhinosinusitis evaluation and follow-up: persistent symptoms despite medical therapy, suspected chronic inflammation, or need to evaluate middle meatus drainage pathways.
• Nasal obstruction where exam is limited and endoscopy is needed to assess turbinate hypertrophy, septal deviation impact, polyps, or mass effect.
• Epistaxis evaluation when the bleeding source is not identified on basic exam.
• Suspected polyps or mass lesions requiring better visualization and characterization.
• Concern for CSF rhinorrhea or other specific pathology where endoscopic visualization contributes to diagnostic workup.
• Post-treatment surveillance of known sinonasal disease where endoscopic findings influence management decisions (e.g., inflammation control, topical therapy adjustment, referral for imaging, biopsy planning). Practical medical-necessity boundary: “Routine” scoping without a clear diagnostic purpose is difficult to defend in audits. The record should state (a) what clinical question prompted endoscopy, and (b) what endoscopy changed (diagnosis confirmed/ruled out, management changed, or a lesion was identified that required further workup). ENT clinical indicators emphasize documenting both the indication and the findings.

2. Medicare & Payer Billing Rules That Drive Denials

CPT 31231 is widely recognized, but claims behavior is dominated by bundling logic, multiple-endoscopy payment rules, and E/M pairing scrutiny. Three payer realities matter most in 2026:

• NCCI bundling and comprehensive-code logic controls whether 31231 is separately payable in mixed-procedure encounters.
• Same-day multiple endoscopy scenarios often require choosing the correct primary procedure rather than stacking multiple diagnostic scope codes.
• E/M + minor procedure billing requires documentation that the E/M is distinct and not merely inherent pre-procedure evaluation.

2.1 “Separate procedure” reality: why it matters operationally

In CPT conventions, procedures labeled or treated as “separate procedures” are commonly considered integral components of a more comprehensive service when performed in the same operative session or anatomic region. In rhinology, diagnostic nasal endoscopy is frequently performed as part of the work necessary to carry out therapeutic endoscopic sinus procedures. CMS NCCI policy for the respiratory system describes bundling expectations and is a practical anchor for understanding when 31231 is not separately reportable.

2.2 Multiple endoscopy payment logic: why “more scopes” does not always mean “more codes”

Otolaryngology encounters sometimes include more than one scope-based service (e.g., nasal endoscopy plus laryngoscopy). In these cases, coding is constrained by both NCCI edits and payer adjudication rules that prevent duplicative payment for overlapping endoscopic work. AAPC’s otolaryngology coding guidance highlights that multiple scopes in one session often do not translate into multiple separately payable codes unless distinctness is supported and payer rules permit separate reporting.

Operational takeaway: When payers deny 31231, the most common root cause is not “lack of coverage” but claim logic conflict (bundling edit, mutually exclusive pairing, or insufficient documentation to support distinctness or E/M separation). Build workflows that review edits and documentation before submission rather than relying on appeals.

3. NCCI Edits, “Separate Procedure” Logic, and Common Bundling Patterns

NCCI policy is the core reference for procedure-to-procedure bundling logic in Medicare and is widely mirrored by commercial payers. For CPT 31231, NCCI-driven denials cluster in two areas: (1) bundling into related therapeutic sinonasal procedures, and (2) scope-to-scope bundling when multiple endoscopies are performed on the same date. CMS NCCI policy manual guidance for respiratory system coding is therefore a primary compliance anchor.

3.1 31231 with endoscopic sinus debridement (31237) and related procedures

A high-frequency denial pattern is reporting diagnostic nasal endoscopy (31231) in addition to therapeutic endoscopic sinonasal services that inherently require endoscopic visualization. AAPC coding guidance explicitly cautions to check CCI edits before coding 31231 with 31237 and indicates they are not typically coded together in the same session for the same site.

• Practical rule: If the clinical service provided is debridement (31237) or another comprehensive endoscopic nasal/sinus procedure, do not “add” 31231 for the diagnostic look that is part of doing the procedure. Instead, code the comprehensive service and ensure the note supports that service.
• Audit lens: Auditors often interpret 31231 billed alongside therapeutic endoscopy as unbundling unless a truly separate, distinct diagnostic endoscopy occurred in a separate session or on a separate anatomic site and payer rules allow it.

3.2 31231 with laryngoscopy on the same date

ENT specialty coding guidance addresses same-day nasal endoscopy and laryngoscopy billing and emphasizes correct code selection and documentation when multiple endoscopic evaluations occur.

If a nasal endoscopy and a laryngoscopy are performed for distinct indications (for example, sinonasal symptoms plus voice/airway complaint), some payers may allow separate reporting when documentation clearly supports two separate diagnostic objectives and when NCCI permits the pairing with an appropriate distinct-procedure modifier. However, “two scopes happened” is not sufficient by itself; the record must show two distinct clinical questions and distinct evaluation content.

3.3 Nasopharyngoscopy (92511) bundling risk

Scope-based ENT codes can overlap anatomically and conceptually. AAPC’s otolaryngology coding guidance highlights that multiple scopes may not justify multiple codes, especially when one scope service encompasses regions that overlap with another code’s diagnostic territory.

Compliance warning: Do not treat modifier 59 as a universal override for same-day scope codes. If the payer’s edit indicators do not permit bypass, or if the services are not truly distinct, appending 59 can create high audit risk.

4. Modifier Usage: 25, 59, 58, 78 (and What to Avoid)

Modifier strategy for 31231 should be conservative and documentation-driven. The most important modifier questions are:

(a) whether an E/M is separately billable, and

(b) whether another procedure performed the same day is distinct enough to allow separate reporting of 31231.

4.1 Modifier 25 on E/M (most common modifier issue)

Because nasal endoscopy is commonly performed in the office, it is often paired with an office E/M (e.g., 99213/99214). The compliance problem is that a portion of the “visit work” (history and focused exam related to the scope, informed consent, and immediate post-procedure discussion) is often considered inherent to the procedure. Guidance on same-day endoscopy billing underscores that modifier 25 should be used only when a significant, separately identifiable E/M service is documented beyond the procedure-related work.

• When 25 is appropriate: A distinct evaluation and management service is performed (separate complaint, separate clinical decision-making, or additional management beyond the scope results), and documentation supports a separate assessment/plan.
• When 25 is risky: The note reads like “scope-only” with minimal separate decision-making, or the E/M appears to describe the same work as the procedure note without additional clinical management.

4.2 Modifier 59 (or XE/XS) for distinct procedures (rare; high scrutiny)

ENT specialty guidance addressing nasal endoscopy and laryngoscopy on the same date emphasizes that distinctness must be clinically meaningful and documented. In practice, modifier 59 (or payer-preferred subset modifiers such as XE/XS) is used when two procedures that normally bundle are truly distinct (separate session, separate anatomic site, or separate clinical indication) and the payer’s edit policy allows a bypass.

High-yield documentation requirement for 59: If you append 59 to 31231, the record should clearly demonstrate (1) a separate indication for nasal endoscopy, (2) a separate indication for the other scope/procedure, and (3) that the scopes were not simply overlapping evaluations performed as one combined endoscopic assessment. ENT guidance highlights careful selection in same-day scope scenarios.

4.3 Modifier 58 and 78 in postoperative/staged contexts (payer-specific and scenario-specific)

Postoperative policies can create confusion about repeat endoscopy during global periods of other procedures. Some payer policies addressing postoperative sinus endoscopy and debridement discuss how modifiers are handled in postoperative contexts and may list modifier restrictions or expectations.

• Modifier 58 (staged/related): Consider when the endoscopy is planned or part of the staged management course related to a prior procedure (documentation should indicate planned staging when applicable).
• Modifier 78 (return to OR): Consider when a patient returns to the operating room for a related procedure during a global period (rare in routine office diagnostic nasal endoscopy contexts, but relevant in surgical practice patterns).

4.4 What to avoid: modifier misuse that creates denials

• Avoid modifier 50 / RT / LT: The code descriptor is unilateral or bilateral; report once per session. ENT clinical indicators emphasize the procedure concept and support documenting laterality clinically without altering reporting to “bilateral.”
• Avoid “stacking scopes” without edit review: AAPC guidance emphasizes that multiple scopes do not automatically justify multiple codes.
• Avoid using modifiers to “force pay”: Distinctness modifiers without clear documentation increase audit exposure rather than solving reimbursement problems.

5. Documentation Standards (Audit-Proofing Checklist)

For CPT 31231, payers and auditors expect documentation to establish medical necessity and to make the endoscopy findings clinically meaningful. ENT clinical indicators provide a strong reference framework for what documentation should include in diagnostic nasal endoscopy.

5.1 Minimum documentation elements

• Indication / reason for the procedure: Symptoms, abnormal findings, surveillance need, or specific diagnostic question.
• Procedure description: Diagnostic nasal endoscopy performed; scope type if relevant (rigid vs flexible); topical anesthesia/decongestion if used (clinical detail supports credibility but is not the CPT code driver).
• Anatomic extent: Structures examined (septum, inferior/middle turbinates, middle meatus, sphenoethmoid recess, nasopharynx if examined).
• Key findings: Normal vs abnormal findings, laterality of pathology, presence/absence of polyps, purulence, masses, bleeding source, crusting, edema, synechiae, postoperative changes, etc.
• Assessment/plan tied to findings: How results influenced treatment (medication changes, imaging ordered, biopsy planned, follow-up interval set).
• Authentication: Provider signature/attestation and date.

5.2 What “audit-proof” documentation looks like

The strongest documentation reads like a diagnostic report rather than a generic template. For example:

• Indication specificity: “Persistent unilateral nasal obstruction and recurrent epistaxis; anterior rhinoscopy limited by swelling—endoscopy performed to identify bleeding source and evaluate for lesion.”
• Findings specificity: “Right: prominent vessels on anterior septum with active oozing; no mass. Left: no bleeding, mild turbinate hypertrophy. Middle meatus: no purulence.”
• Management linkage: “Plan: cauterization deferred today; initiate topical therapy; consider imaging if symptoms persist; return in 2 weeks.” Common documentation failure that triggers denials: A note that states “nasal endoscopy performed” but does not include the clinical indication and does not record findings. ENT clinical indicators emphasize documenting indication and findings as core elements.

5.3 Documentation when billing E/M + 31231

If an E/M is billed with modifier 25, the documentation should demonstrate a distinct E/M service (separate problem, additional management beyond the scope, or significant decision-making independent of the procedure). Same-day endoscopy billing guidance emphasizes that the E/M must be “separately identifiable” and documented as such.

6. ICD-10 Diagnosis Support: Practical Indication Mapping

ICD-10 selection should reflect the reason the endoscopy was needed, not merely a general symptom when a more specific diagnosis is known or suspected. ENT clinical indicators provide a practical lens: the indication should justify why endoscopic visualization was clinically necessary.

Examples of ICD-10 categories often used to support diagnostic nasal endoscopy include:

• Chronic rhinosinusitis: chronic sinusitis codes (e.g., chronic maxillary/frontal/ethmoidal/sphenoidal patterns) when evaluation is for chronic inflammatory disease assessment.
• Nasal polyps: when endoscopy is used to identify or monitor polyp burden.
• Epistaxis: when endoscopy is needed to locate a bleeding source not visible on anterior exam.
• Nasal obstruction / turbinate hypertrophy / structural complaints: when scope is required to evaluate posterior structures or rule out lesion.
• Suspected mass / neoplasm evaluation: when diagnostic visualization is part of a workup plan (endoscopy findings may drive biopsy or imaging).
• CSF rhinorrhea workup: when clinically suspected and endoscopic evaluation is part of diagnostic workup. Practical ICD-10 rule: Do not “upcode” the diagnosis to justify the procedure. Use the diagnosis that truthfully reflects the indication (symptom-based if that is all that is known, or disease-based if established). The record should support the diagnosis selection and the rationale for endoscopic evaluation.

7. Comparison Table: 31231 vs 31237 vs 31575 vs 92511

8. Real-World Clinical Scenarios and Clean Coding Examples

Scenario 1: Chronic rhinosinusitis symptoms not explained by anterior rhinoscopy

Setting: Office ENT visit.

Presentation: Months of facial pressure, purulent drainage, and reduced smell; anterior rhinoscopy limited by edema.

Service: Diagnostic nasal endoscopy performed to evaluate middle meatus and drainage pathways; purulence and edema documented; plan includes targeted medical therapy and imaging consideration.

Coding logic: Report 31231 once. If a separately identifiable E/M was performed (e.g., management of comorbid conditions, separate complaint, or significant decision-making), report E/M with -25 supported by distinct documentation.

Scenario 2: Epistaxis with unclear bleeding source

Setting: Office or outpatient clinic.

Presentation: Recurrent unilateral epistaxis; no anterior source visualized.

Service: Diagnostic nasal endoscopy identifies posterior septal vessel; findings documented; management plan created (topical therapy, cautery planning, or further workup).

Coding logic: Report 31231 once. Documentation should clearly state why endoscopy was needed and what was found; ENT clinical indicators emphasize documenting indication and findings.

Scenario 3: Same-day nasal endoscopy and laryngoscopy for separate complaints

Setting: ENT office.

Presentation: Chronic nasal obstruction plus a separate voice complaint (hoarseness) requiring laryngeal evaluation.

Service: Nasal endoscopy performed for sinonasal evaluation; diagnostic laryngoscopy performed for hoarseness workup.

Coding logic: Follow ENT guidance for same-day nasal endoscopy and laryngoscopy. If separately reportable under payer edits, documentation must clearly support distinct indications and distinct evaluation content. Use distinct-procedure modifiers only when appropriate and supported.

Scenario 4: Postoperative sinonasal management (payer policy sensitivity)

Setting: Postoperative follow-up after prior sinonasal surgery.

Service: Endoscopic evaluation is performed as part of postoperative management; payer policy may distinguish diagnostic evaluation from debridement and may impose modifier and global-period rules depending on the prior procedure.

Coding logic: Ensure the code billed matches the service performed (diagnostic evaluation vs debridement) and follow payer postoperative policy guidance where applicable.

Scenario 5: Attempted “bilateral” billing error

Setting: Office.

Service: Nasal endoscopy performed on both sides.

Common error: Reporting 31231 with modifier 50 or billing two units for “right and left.”

Correct approach: Report 31231 once and document bilateral findings in the procedure note. ENT clinical indicators and CPT descriptor logic support one-line reporting.