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31231

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⚕️CPT Code 31231 - Nasal endoscopy, diagnostic, unilateral or bilateral

Long description: Nasal endoscopy, diagnostic, unilateral or bilateral (separate procedure).web:7
This code represents diagnostic endoscopic evaluation of the nasal cavity (and visualized sinus outflow tracts) performed with rigid or flexible endoscopes, typically under topical anesthesia in the office or outpatient setting.web:6

Clinical use and indications

Diagnostic nasal endoscopy is used to better characterize nasal and paranasal sinus anatomy and identify sinonasal pathology that cannot be adequately assessed with anterior rhinoscopy alone.web:6
Common indications include evaluation of chronic sinonasal symptoms, assessment of response to medical or surgical therapy, surveillance for recurrent sinusitis or nasal polyps, evaluation of epistaxis, endoscopically guided cultures, assessment of facial pain of possible rhinogenic origin, clear rhinorrhea suggestive of cerebrospinal fluid leak, sinonasal neoplasm evaluation, and smell disorders.web:6

The procedure is commonly performed in the otolaryngology clinic after topical decongestion and anesthesia, using a 0-30 degree rigid endoscope or flexible endoscope to inspect the septum, inferior and middle turbinates, middle meatus, sphenoethmoid recess, and nasopharynx when accessible.web:6
Findings may include mucosal edema, purulence, polyps, crusting, septal deviation, postoperative changes, mass lesions, or evidence of CSF leak, and both normal and abnormal findings should be documented to support medical necessity and avoid denials.web:5

Work RVU and reimbursement considerations

For recent Medicare fee schedules, 31231 is a low-intensity minor procedure with work RVU of approximately 1.0 and total RVU around the mid‑1 range, varying slightly by year and locality.web:3
It carries a 0‑day global period (global period 000), which means evaluation and management services on the same day must be separately identifiable and supported for modifier 25 use when appropriate.web:2

Because the code is valued as a stand‑alone minor procedure, payers consider a small, inherent E/M component included in its valuation, so documentation must clearly distinguish any additional E/M service if billed separately.web:2
Assistant surgeon services are not payable for 31231 under Medicare (assistant-at-surgery indicator N), which is expected given the office-based, low-complexity nature of the service.web:3

Assistant at surgery and team surgery

Medicare’s assistant-at-surgery indicator for 31231 is “N,” indicating that assistant surgeon claims will be denied as not covered.web:3
The procedure is typically performed by a single otolaryngologist without the need for co-surgeon or team surgeon arrangements, so team surgery indicators similarly do not support additional surgeon roles under standard policy.web:3

When nasal endoscopy is performed in an operative setting as a true diagnostic procedure rather than as part of a more extensive endoscopic sinus surgery, the same assistant restrictions apply, and the diagnostic endoscopy remains bundled into more extensive endoscopic codes in most circumstances.web:7

Includes / inherent components

By convention, this diagnostic endoscopy includes the following components:web:6web:7

  • Use of topical decongestant and anesthetic in the nasal cavity.
  • Introduction of endoscope with systematic inspection of the nasal cavity and accessible sinus outflow tracts.
  • Limited manipulation necessary to visualize anatomic landmarks (e.g., gentle lateralization of turbinates).
  • Routine documentation of findings and patient tolerance.

It is also considered integral to more extensive endoscopic sinus procedures in the same anatomic region and is not separately reported when used solely to guide or confirm the therapeutic procedure (e.g., FESS on the same side).web:7

Excludes / when not separately reportable

31231 is not separately reportable in the following common scenarios:web:7web:8

  • When performed as part of more extensive nasal/sinus endoscopic surgery in the same anatomic region (e.g., endoscopic ethmoidectomy, maxillary antrostomy) during the same session.
  • When used solely as a diagnostic or guidance step integral to another nasal/sinus endoscopic procedure on the same side.
  • When payer NCCI edits bundle it into certain laryngoscopy procedures, unless separate scopes, distinct indications, and different anatomic regions are clearly documented and modifier 59/XS is appropriately supported.

31231 also should not be reported for simple anterior rhinoscopy performed with a nasal speculum and headlight; in that case, the exam is part of the E/M service rather than an endoscopy.web:6

Code family / “code tree” context

Within the nasal endoscopy family, 31231 functions as the base code for diagnostic nasal endoscopy that does not include debridement or specific therapeutic interventions.web:7
Other codes in the family describe additional work such as sinusotomy, debridement, or control of epistaxis and typically encompass the diagnostic visualization inherent in 31231.web:7

Common related nasal endoscopy codes (simplified “tree” perspective):web:7web:8

  • 31231 - Diagnostic nasal endoscopy, unilateral or bilateral (separate procedure).
  • 31233 - Nasal/sinus endoscopy with biopsy, polypectomy, or debridement limited to certain sites (varies by descriptor; consult full code set).
  • 31235 - Nasal/sinus endoscopy with additional sinus evaluation/intervention (see full descriptor).
  • 31237 - Nasal/sinus endoscopy, surgical with debridement (e.g., postoperative FESS cavity cleaning).
  • 31238 - Nasal/sinus endoscopy, surgical, with control of nasal hemorrhage (epistaxis).

Tip

Endoscopy multiple-procedure rules treat 31231 as the base diagnostic endoscopy that is “built into” higher-valued nasal/sinus endoscopy codes, explaining why it is “never paid separately” when a more extensive code in the same family is reported for the same site.web:7

Modifiers commonly associated with 31231

While specific use depends on payer policy and documentation, the following modifiers are frequently relevant to 31231 in ENT practice:web:2web:7

  • 25 - Significant, separately identifiable E/M service by the same physician on the same day of the procedure or service (used on E/M code, not on 31231).
  • 59 - Distinct procedural service (used on 31231 when performed at a different session, different site/structure, or distinct indication from another endoscopy and allowed by payer policy).
  • XS - Separate structure (Medicare X modifier; may be preferred over 59 when distinguishing separate anatomic structures).

Careful documentation must support why the diagnostic endoscopy is distinct from any other endoscopic or surgical procedure billed on the same date, especially when invoking 59 or XS.web:7

Typical ICD-10-CM diagnosis pairings (no HCC impact)

CPT 31231 itself is a procedure code and does not directly map to an HCC, but the associated ICD-10-CM diagnosis codes determine risk adjustment and medical necessity.
Most sinonasal conditions evaluated with diagnostic nasal endoscopy fall into non‑HCC respiratory or ENT categories, so this procedure rarely drives HCC capture; however, accurate coding supports overall documentation integrity.web:3

Common ICD-10-CM codes used with 31231 in ENT practice (examples):web:3web:9

  • J01.90 - Acute sinusitis, unspecified: used when acute sinus infection is present without specified site.
  • J31.0 - Chronic rhinitis: chronic nasal mucosal inflammation, often allergic or vasomotor.
  • J32.9 - Chronic sinusitis, unspecified: for chronic sinus inflammation when specific sinus is not documented.
  • J34.2 - Deviated nasal septum: supports evaluation of nasal obstruction due to septal deformity.
  • R09.81 - Nasal congestion: symptom-based code when no definitive diagnosis is yet established.

Tip

For chronic rhinosinusitis with nasal polyps (CRSwNP), more specific ICD-10-CM coding (e.g., J33 family plus chronic sinusitis codes) better reflects disease phenotype, which can be clinically important because nasal polyposis is associated with higher disease burden and different inflammatory patterns.web:4web:9

MS-DRG context

CPT 31231 is most frequently performed in the outpatient or office setting and thus does not itself define an MS‑DRG, but when performed during a hospital inpatient stay, the MS‑DRG is driven by the principal ICD-10-CM diagnosis and any inpatient procedural codes (ICD‑10‑PCS) rather than this CPT code.web:10
Inpatients with principal diagnoses such as chronic sinusitis, epistaxis, or sinonasal neoplasm would typically group into medical DRGs for ear, nose, mouth, and throat conditions unless a qualifying major operative procedure (coded in ICD‑10‑PCS) is performed that moves the case into a surgical DRG.web:10

As a purely diagnostic, low‑risk endoscopic evaluation, 31231 on its own does not usually correspond to an ICD‑10‑PCS “major OR” procedure and therefore rarely changes MS‑DRG assignment when translated into inpatient coding terms.web:10

Coding examples

Example 1 - Chronic rhinosinusitis surveillance

An established patient with a history of chronic sinusitis and prior FESS returns with persistent nasal congestion and postnasal drip despite guideline-directed medical therapy.
After topical decongestant and anesthetic, the otolaryngologist performs bilateral diagnostic nasal endoscopy, visualizing the middle meatus, sphenoethmoid recess, and postoperative cavities, documenting mucosal edema and small polypoid changes but no purulence.

  • Procedure code: 31231
  • Example diagnosis codes: J32.9 (chronic sinusitis, unspecified), R09.81 (nasal congestion) as appropriate.

Because the visit includes detailed interval history, medication review, and decision-making about further medical vs surgical management beyond what is inherent to the endoscopy, the provider also reports an established patient E/M with modifier 25 if documentation supports a significant, separately identifiable service.web:2

Example 2 - Epistaxis evaluation without cautery

A patient presents with intermittent unilateral epistaxis and nasal obstruction.
Anterior rhinoscopy is inconclusive, so after topical vasoconstrictor and anesthetic, the ENT performs unilateral diagnostic nasal endoscopy, identifying a small friable area on the anterior septum without active bleeding and no other structural lesions.

  • Procedure code: 31231
  • Example diagnosis codes: R04.0 (epistaxis), plus J34.2 (deviated nasal septum) if documented.

If no cauterization or specific hemorrhage control is performed, 31231 alone describes the procedure.
If cautery is performed endoscopically to control active bleeding, a surgical nasal endoscopy code such as 31238 may be more appropriate, and 31231 would generally not be separately reported for that same site and session due to NCCI bundling.web:7web:8

Example 3 - Separate diagnostic endoscopy and FESS on different sites

A patient undergoes endoscopic maxillary antrostomy on the right side for chronic maxillary sinusitis, and during the same session the surgeon also performs diagnostic nasal endoscopy on the contralateral (left) nasal cavity for separate symptoms of obstruction.
Operative documentation clearly distinguishes the right-sided therapeutic sinus surgery from the left-sided diagnostic evaluation, including separate indications and findings.

  • Procedure codes:
    • FESS procedure code(s) for right-sided sinus surgery (e.g., right maxillary antrostomy code as appropriate).
    • 31231-59 or 31231-XS for left-sided diagnostic endoscopy when allowed by payer policy.

This scenario reflects the “separate structure” use case where 31231 can be unbundled from more extensive sinus endoscopy because it is performed on a different side/structure with a distinct clinical indication and documentation.web:7

Sources

web:2 AAPC - My Otolaryngology Coding Alert discussion of 31231 and E/M bundling.
web:3 ENT diagnosis and procedure code utilization overview (Top ENT Codes).
web:5 ENT coding article on diagnostic endoscopy denials and documentation tips.
web:6 American Rhinologic Society position statement on diagnostic nasal endoscopy (31231).
web:7 Nasal endoscopy billing and coding updates describing 31231 as base code and bundling rules.
web:8 AAPC guidance on reporting 31238 and 31231 together under NCCI edits.
web:9 Patient-focused CRSwNP resource describing chronic inflammation and nasal polyps.
web:10 CMS MS‑DRG definitions manual for ENT medical DRGs.

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