CurrentPremera BluecrossPolicy 7.01.559

Sinus Surgery in Adults (FESS and Balloon Ostial Dilation)

Medical policy defining medical necessity criteria, documentation requirements, coding, site-of-service rules, and evidence review for elective sinus surgical procedures (Functional Endoscopic Sinus Surgery and Balloon Ostial Dilation) in individuals aged 19 and older; includes indications, preoperative medical therapy requirements, and when site-of-service pre-approval is required.

Policy Summary

PayerPremera Bluecross

PolicySinus Surgery in Adults (FESS and Balloon Ostial Dilation)

Policy CodePolicy 7.01.559

Change TypeMixed (multiple additions/removalsannual updates)

Effective DateMay 1, 2026

Next Review Date

Key ActionObtain health plan pre-approval for sinus surgery performed outside a hospital OR and document onset/duration, maximal medical therapy tried and failed, and CT/MRI or nasal endoscopy results showing objective sinus disease.

SourceLink

POLICY UPDATE CHANGES

Policy history shows multiple implementation delays and iterative updates between 2014 and 2016 and interim reviews with additions (e.g., age 19+, balloon dilation indications).

Silent sinus syndrome (chronic maxillary atelectasis) added to list of conditions for which FESS may be considered medically necessary.

Maxillary accessory ostium/ostia (ostiomeatal complex) added to imaging findings associated with chronic rhinosinusitis.

Policy updated annually with literature reviews and references; policy statements largely unchanged across reviews.

CPT codes 31233, 31235, 31240 removed from policy.

Site of Service Ambulatory Service Center (ASC) Select Surgical Procedures criteria added and related policy 11.01.525 referenced.

Policy language standardized replacing 'patient' with 'individual' throughout the policy.

Policy updated to indicate site of service review does not apply to Indian Health Services (IHS) facilities.

Trek Health ingests and normalizes Transparency in Coverage data and payer policy updates to give provider organizations a clear view of how commercial reimbursement behaves across markets, payers, and services. Our platform transforms raw payer disclosures into structured intelligence that supports contract evaluation, payer negotiations, and service line strategy. By combining market benchmarks with ongoing policy visibility, Trek helps teams identify variability, risk, and opportunity in commercial reimbursement. The result is faster insight, stronger negotiating positions, and more informed financial decisions.

Coverage Summary

Scope: This policy (Sinus Surgery in Adults, policy 7.01.559) defines medical necessity criteria, documentation requirements, coding, site-of-service rules, and evidence review for elective sinus surgical procedures in individuals aged 19 and older (adults). Effective date is May 1, 2026 with last revision June 1, 2026.

Subject and population: The policy addresses surgical management of chronic rhinosinusitis (CRS) and recurrent acute bacterial rhinosinusitis (RARS) in adults (Age ≥19) and covers both Functional Endoscopic Sinus Surgery (FESS) and Balloon Ostial Dilation (BOD / balloon sinuplasty) as treatment options.

High-level coverage stance: Mixed — the policy includes detailed medical necessity criteria that make FESS and BOD medically necessary in specified situations; evidence supports both procedures but with differing indications and levels of evidence (e.g., RCTs/meta-analyses supporting BOD non-inferiority and variable evidence for FESS), so coverage depends on meeting the stated criteria.

Covered procedures and requirements: FESS and BOD (balloon ostial dilation) are addressed with associated CPT/HCPCS codes listed; a site-of-service medical necessity review applies for elective sinus surgery (preferred ASC when appropriate, with exceptions) and site-of-service pre-approval is required when surgery is not performed in a hospital operating room.

Key thresholds and quick facts

Duration of CRS symptoms>= 12 continuous weeks

RARS episode frequency>= 4 episodes within 12 continuous months

Antibiotic course requirementAt least one 5-7 day course of oral antibiotics within the last 6 months (varies by indication)

Topical steroid / saline requirementTopical intranasal steroids OR daily saline nasal irrigation for at least 6 consecutive weeks (4 weeks used in some RARS documentation requirements)

ASC accessibility threshold (site of service)No qualifying ambulatory surgical center within 30 miles that can provide necessary care or where physician has privileges

Medical-Necessity Criteria

Functional Endoscopic Sinus Surgery (FESS) - Recurrent Acute Bacterial Rhinosinusitis (RARS)

Functional Endoscopic Sinus Surgery (FESS) — Recurrent Acute Bacterial Rhinosinusitis (RARS).

Functional endoscopic sinus surgery (FESS) may be considered medically necessary when ALL of the following are met:

1) Four or more documented episodes of acute bacterial rhinosinusitis within 12 continuous months.

2) Documentation of episodes including date, clinician diagnosis, and antibiotic treatment for each episode.

3) There is objective evidence of sinus disease as demonstrated by ONE of the following:

a) Sinus CT or MRI showing mucosal thickening, polyps, opacification of the paranasal sinuses, sinus ostial obstruction, or air-fluid levels; OR

Clinical Definitions, Diagnostic Criteria, and Appropriateness

Coding

Covered CPT codes for FESS and BOD proceduresCPTCovered

31253	Nasal/sinus endoscopy, surgical with ethmoidectomy; total (anterior and posterior), including frontal sinus exploration, with removal of tissue from frontal sinus, when performed.
31254	Nasal/sinus endoscopy, surgical; with ethmoidectomy, partial (anterior).
31255	Nasal/sinus endoscopy, surgical; with ethmoidectomy, total (anterior and posterior).
31256	Nasal/sinus endoscopy, surgical, with maxillary antrostomy.
31257	Nasal/sinus endoscopy, surgical with ethmoidectomy; total (anterior and posterior), including sphenoidotomy.
31259	Nasal/sinus endoscopy, surgical with ethmoidectomy; total (anterior and posterior), including sphenoidotomy, with removal of tissue from the sphenoid sinus.
31267	Nasal/sinus endoscopy, surgical, with maxillary antrostomy; with removal of tissue from maxillary sinus.
31276	Nasal/sinus endoscopy, surgical with frontal sinus exploration, with or without removal of tissue from frontal sinus.
31287	Nasal/sinus endoscopy, surgical, with sphenoidotomy.
31288	Nasal/sinus endoscopy, surgical, with sphenoidotomy; with removal of tissue from the sphenoid sinus.

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HCPCS material/device code for balloon catheterHCPCSCovered

C1726

Catheter, balloon dilatation, nonvascular

FDA-cleared balloon sinus dilation devices (device list, informational)mixed

K190525	Relieva Ultirra Sinus Balloon Catheter - 510(k) No.
K181838	Sinusway Dilation System - 510(k) No.
K172737	MESIRE - Balloon Sinus Dilatation System - 510(k) No.
K171687	Relieva SpinPlus Nav Balloon Sinuplasty System - 510(k) No.
K161698	Relieva UltirraNav Sinus Balloon Catheter - 510(k) No.
K160770	Vent-Os Sinus Dilation Family - 510(k) No.
K153341	Relieva Scout Multi-Sinus Dilation System - 510(k) No.
K152434	XprESS Multi-Sinus Dilation System - 510(k) No.
K143738	DSS Sinusplasty Balloon Catheter - 510(k) No.
K143541	Relieva SpinPlus Balloon Sinuplasty System - 510(k) No.

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CPT codes historically added/removed/updated in policy historyCPT

31233	CPT code added 05/01/25 then removed 08/01/25 per history.
31235	CPT code added 05/01/25 then removed 08/01/25 per history.
31240	CPT code added 05/01/25 then removed 08/01/25 per history.
31241	CPT code added 01/23/18 (new codes effective 1/1/18).
31253	CPT code added 01/23/18 (new codes effective 1/1/18).
31257	CPT code added 01/23/18 (new codes effective 1/1/18).
31259	CPT code added 01/23/18 (new codes effective 1/1/18).
31295	Descriptor revised 01/01/20.
31296	Descriptor revised 01/01/20.
31297	Descriptor revised 01/01/20.

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HCPCS addedHCPCS

C1726

HCPCS code added 11/01/20.

Provider Actions and Billing Rules

Prior Authorization

Site-of-service pre-approval required for non-hospital OR sinus surgery

Sinus surgery performed outside a hospital operating room (e.g., ASC or office-based procedure) requires health plan pre-approval. Prior to scheduling non-hospital OR sinus surgery, obtain site-of-service medical necessity review and explicit plan approval to confirm that the chosen setting is appropriate for the individual's clinical risk and the planned procedures.

Site-of-service review required for non-hospital OR sinus surgery (effective 2026-05-01).
Site-of-service medical necessity criteria do not apply to Indian Health Services (IHS) facilities (see note: does not apply to IHS).

Documentation Required

Confirm diagnostic criteria and imaging

Document that the individual meets diagnostic criteria for chronic rhinosinusitis (CRS) or recurrent acute rhinosinusitis (RARS) and obtain fine-cut sinus CT imaging prior to balloon dilation or surgical planning. Record objective findings (CT or nasal endoscopy) that correspond to the clinical symptoms and that support the surgical indication.

Background and Evidence Summary

Background and purpose: This coverage policy specifies indications and objective diagnostic thresholds (e.g., CRS symptoms ≥ 12 continuous weeks, RARS defined as ≥ 4 episodes in 12 months), required preoperative/maximal medical therapy (examples include at least one 5–7 day course of oral antibiotics within the prior 6 months and topical intranasal steroids or daily saline irrigation for specified durations), documentation requirements (onset/duration, imaging or endoscopy, documentation of medical therapy failure), and site-of-service considerations (preferred Ambulatory Surgical Center when appropriate; site-of-service review and pre-approval for non-hospital OR cases).

Relationship to guidelines: The policy aligns with and cites professional guidance—AAO-HNS recommendations (verify CRS diagnosis, assess candidacy, obtain fine-cut CT for surgical planning, and guidance on patient selection and perioperative care) and NICE guidance (e.g., XprESS MTG30 finding supporting balloon dilation as comparable to FESS in selected uncomplicated CRS after failed medical therapy)—and incorporates AAO-HNS consensus statements on balloon dilation appropriateness and operational recommendations. The policy applies to adults age 19+.

Evidence source	Key finding
REMODEL RCT durability	BOD non-inferior to FESS with durable effect to 24 months (REMODEL)
Meta-analysis (14 RCTs)	BOD associated with lower postoperative SNOT-20, shorter operating time, and fewer complications vs FESS; no difference in revision surgery or Lund-Mackay scores
Complication rates (retrospective cohort)	Retrospective cohort: overall complication rate 5% for BOD vs 7% for FESS
AAO-HNS recommendation strength	Multiple strong recommendations on diagnosis verification, imaging, candidacy, and perioperative care; consensus statements on appropriate use of balloon dilation
NICE 2016 finding (MTG30)	XprESS supported as comparable to FESS for uncomplicated chronic sinusitis after failed medical therapy (based on REMODEL); faster recovery and more local anesthesia use

Device/technology context: The policy lists multiple FDA-cleared balloon sinus dilation devices and references HCPCS/CPT coding for balloon dilation (e.g., HCPCS C1726 and CPT codes in the 3129x series for dilation).

Reuse/reprocessing: Per AAO-HNS operational recommendations referenced in the policy, surgeons who consider reusing devices intended for dilation should follow FDA reprocessing regulations (strong consensus statement).

Medicare Determinations

Determination	Effective/Notes
Medicare National Coverage: No national coverage determination	No national coverage determination exists for balloon dilation or sinus surgery; policy notes 'There is no national coverage determination.'

Definitions

Chronic rhinosinusitis (CRS)Symptoms > 12 weeks with >=2 symptoms (one must be nasal blockage/obstruction or nasal discharge) plus objective endoscopic or CT evidence of inflammation.

Recurrent acute rhinosinusitis (RARS)Four or more episodes of acute bacterial rhinosinusitis per year without persistent symptoms between episodes.

Maximal medical therapyTypically includes topical intranasal steroids and antibiotics; policy specifies at least one 5-7 day course of oral antibiotics and topical intranasal steroids OR daily saline irrigation for specified durations.

ASA classificationAmerican Society of Anesthesiologists physical status scoring (ASA 1-5) as defined in policy (ASA1 healthy to ASA5 moribund).

CRS subtypes (CRSwNP / CRSsNP)CRSwNP = CRS with nasal polyps; CRSsNP = CRS without nasal polyps (based on presence or absence of nasal polyps).

Revision History

2014-12-08revised (history)

New policy created and added to Surgery section; planned provider notification and effective date originally set for 2015-04-15 with subsequent implementation delays throughout 2015.

2016-05-01revised (history)

Annual review approved April 18, 2016; policy updated with removal of 'without medical review' for list of medically necessary indications and addition of revision surgery to list of indications.

2016-08-01revised (history)

Policy Summary

PayerPremera Bluecross

PolicySinus Surgery in Adults (FESS and Balloon Ostial Dilation)

Policy CodePolicy 7.01.559

Change TypeMixed (multiple additions/removalsannual updates)

Effective DateMay 1, 2026

Next Review Date

SourceLink

On This Page

Functional Endoscopic Sinus Surgery (FESS) - Chronic Rhinosinusitis (CRS) with or without polyposis (Initial surgery)

Functional Endoscopic Sinus Surgery (FESS) — Chronic Rhinosinusitis (CRS) with or without polyposis (Initial surgery).

Functional endoscopic sinus surgery (FESS) may be considered medically necessary when ALL of the following are met:

1) Chronic rhinosinusitis symptoms (e.g., mucopurulent drainage, nasal congestion/obstruction, facial pain/pressure, decreased sense of smell) have been present for at least 12 continuous weeks.

2) Medical therapy consisting of BOTH of the following has been tried and failed:

a) At least one 5-7 day course of oral antibiotics within the last 6 months; AND

b) Topical intranasal steroids OR daily saline nasal irrigation for at least 6 consecutive weeks.

3) There is objective evidence of sinus disease as demonstrated by ONE of the following:

a) Sinus CT or MRI showing significant mucosal thickening, polyps, opacification of the paranasal sinuses, sinus ostial obstruction, maxillary accessory ostium/ostia, presence of accessory ostia, or air-fluid levels; OR

b) Nasal endoscopy shows purulent mucus or edema in the middle meatus, anterior ethmoid region, or sphenoethmoid region, or polyps in the nasal cavity or middle meatus.

Operational note: Depending on symptoms and imaging findings, surgery could be unilateral or bilateral.

Documentation requirements: include symptom duration, prior medical therapy details (dates, medications, adherence), imaging and/or endoscopy reports, and clinician assessment linking symptoms to objective findings.

Functional Endoscopic Sinus Surgery (FESS) - Revision surgery

Functional Endoscopic Sinus Surgery (FESS) — Revision surgery.

Functional endoscopic sinus surgery (FESS) may be considered medically necessary for revision surgery when ALL of the following are met:

1) At least 12 weeks have passed since the previous sinus surgery.

2) Chronic rhinosinusitis symptoms (e.g., mucopurulent drainage, nasal congestion/obstruction, facial pain/pressure, decreased sense of smell) have been present for at least 12 continuous weeks since recurrence of symptoms.

3) Medical therapy consisting of the following has been tried and failed since the previous surgery:

a) At least one 5-7 day course of oral antibiotics; AND

b) Additional appropriate medical therapy as clinically indicated (e.g., topical intranasal steroids or saline irrigation).

4) There is persistent objective evidence of sinus disease as demonstrated by ONE of the following:

a) Sinus CT or MRI showing significant mucosal thickening, polyps, opacification of the paranasal sinuses, sinus ostial obstruction, accessory ostia, or air-fluid levels; OR

b) Nasal endoscopy shows purulent mucus or edema in the middle meatus, anterior ethmoid region, or sphenoethmoid region, or polyps in the nasal cavity or middle meatus.

Documentation requirements: include prior operative report with date, documentation that >=12 weeks have elapsed, records of post-operative medical therapy and antibiotics, current imaging and/or endoscopy demonstrating persistent disease, and rationale for revision rather than continued medical therapy.

FESS - Other diagnoses considered medically necessary

FESS — Other diagnoses considered medically necessary.

FESS may be considered medically necessary for ANY of the following diagnoses when clinically appropriate:

• Abscess (complication of sinusitis)

• Cerebrospinal fluid (CSF) leak closure

• Choanal atresia repair

• Concha bullosa, symptomatic

• Dacryocystorhinostomy (DCR)

• Epistaxis control

• Excision of selected tumors and nasal masses

• Foreign body removal

• Nasal polyps, multiple (antrochoanal polyps)

• Optic nerve decompression

• Orbital decompression (e.g., Graves ophthalmopathy)

• Recurrent sinusitis in persons with cystic fibrosis or severe asthma

• Silent sinus syndrome (chronic maxillary atelectasis, Stage III) confirmed by paranasal sinus CT

• Sinonasal tumor

• Sinus mucocele, symptomatic

• Sinus disease with bone erosion

• Sinus disease in the immunocompromised

• Invasive fungal sinus disease

• Allergic fungal sinus disease

• Sinus disease related to Wegener's granulomatosis (granulomatosis with polyangiitis)

• Sinus disease related to hereditary hemorrhagic telangiectasia

• Sinus disease related to scarring or osteoneogenesis

Documentation requirements: include diagnosis-specific imaging, pathology, or specialty consultation reports as applicable.

Balloon Sinus Ostial Dilation (BOD) - Chronic Rhinosinusitis and RARS

Balloon Sinus Ostial Dilation (BOD) — Chronic Rhinosinusitis and Recurrent Acute Bacterial Rhinosinusitis (RARS).

Balloon sinus ostial dilation (BOD) may be considered medically necessary when ALL of the following are met (standalone BOD):

1) Diagnosis of chronic rhinosinusitis meeting the CRS criteria above OR diagnosis of recurrent acute bacterial rhinosinusitis meeting the RARS criteria above; AND

2) Medical therapy as specified for CRS or RARS has been tried and failed; AND

3) Objective evidence of sinus ostial obstruction appropriate for dilation as demonstrated by imaging or endoscopy.

Adjunctive use / billing and coding considerations (ANY of the following applicable scenarios):

• BOD performed as an integral part of FESS during the same operative session: BOD is considered integral when dilation is used to facilitate endoscopic access or restore ostial patency as part of a planned FESS. Billing note: when integral to FESS, carrier-specific billing rules apply and separate reimbursement for BOD may be limited or denied per coding guidance.

• BOD performed as an adjunct to FESS for targeted dilation of an ostium in addition to standard endoscopic procedures: document medical necessity and rationale for adjunctive use; billing may vary by payer.

• BOD as a standalone procedure may be considered when criteria above for standalone use are met and when imaging/endoscopy localize disease amenable to dilation without the need for tissue removal.

Documentation requirements: include pre-procedure imaging/endoscopy demonstrating ostial obstruction, documentation of prior medical therapy, operative report detailing whether BOD was standalone or integral/adjunct to FESS, and coding/billing rationale.

Operational billing rule: verify payer-specific guidance for separate claims and allowable CPT/HCPCS codes when BOD is performed with FESS versus as a standalone procedure; anticipate prior authorization and potential denial risk if documentation does not clearly support standalone indication or adjunctive necessity.

Site of Service Medical Necessity

Site of Service Medical Necessity (applies across above procedures).

Medically necessary sites of service for elective sinus procedures (including FESS and BOD):

• Ambulatory Surgical Center (ASC) — preferred site when appropriate and available.

• Off-campus outpatient hospital/medical center when no geographically accessible ASC with necessary equipment or physician privileges is available, or ASC guidelines prohibit use for the individual's condition or weight.

• On-campus outpatient hospital/medical center when ASC access is not available or when patient-specific factors require hospital outpatient department.

Site of service NOT medically necessary when the above criteria are not met:

• Inpatient hospital/medical center is considered NOT medically necessary for elective sinus procedures unless patient meets criteria for inpatient care (e.g., increased anesthesia or medical risk, concurrent procedures requiring hospital setting, pregnancy, morbid obesity with BMI >=50, bleeding disorder requiring replacement products, anticipated transfusion, end stage organ disease as specified in policy).

Clinical/medical risk considerations that may justify hospital outpatient or inpatient site of service include (examples):

• Anesthesia risk: ASA class III or higher, prior anesthesia complications, alcohol dependence or history of cocaine use, anticipated prolonged surgery (>3 hours).

• Cardiovascular risk: uncompensated CHF (NYHA III/IV), recent MI (<3 months), poorly controlled/resistant hypertension (>=3 drugs), recent stroke (<3 months), recent drug-eluting stent (<1 year) or angioplasty (<90 days), symptomatic arrhythmia, significant valvular disease.

• Liver risk: advanced liver disease (MELD >8).

• Pulmonary risk: severe COPD, moderate-severe OSA (AHI >=15).

• Renal risk: end-stage renal disease on dialysis.

Documentation requirements: include clinical justification for site selection, relevant comorbidity documentation (e.g., ASA class, cardiology/pulmonary consults), and confirmation that ASC was unavailable or inappropriate when hospital outpatient site is used. Note: Site of Service criteria do not apply to Indian Health Services (IHS) facilities.

Documentation Required

Documentation required for RARS

For recurrent acute rhinosinusitis (RARS), document the frequency and timing of episodes and confirm prior medical management. Required documentation includes onset and duration of current and prior episodes, evidence of four or more acute bacterial rhinosinusitis episodes within 12 months (when applicable), details of maximal medical therapy attempted including at least one course of oral antibiotics (5–7 days) within the last 6 months, and the results of sinus CT/MRI or nasal endoscopy.

Onset and duration of symptoms and number of acute episodes (≥4 in 12 months when applicable).
Maximal medical therapy: at least one 5–7 day course of oral antibiotics within last 6 months, and topical intranasal steroids or daily saline irrigation.
Objective findings: fine-cut CT or MRI showing mucosal disease/obstruction or nasal endoscopy showing purulence/edema or polyps.

Documentation Required

Documentation required for CRS (initial and revision)

For initial CRS and for revision CRS surgeries, document duration of symptoms, prior medical therapy, and objective findings. For revision procedures include surgery-specific timing and interim treatment details to justify surgical extent.

CRS initial: symptoms ≥12 continuous weeks; at least one 5–7 day antibiotic course within last 6 months; topical intranasal steroids OR daily saline irrigation for at least 6 consecutive weeks; objective evidence by CT/MRI or nasal endoscopy.
Revision CRS additional requirements: at least 12 weeks since prior sinus surgery; at least one 5–7 day course of antibiotics since the prior surgery; documentation of persistent objective disease on CT/MRI or endoscopy.
Include clear operative planning documentation that links targeted sinuses and extent of surgery to symptoms and imaging. Surgical extent justification must explain why the planned procedures (e.g., which sinuses, unilateral vs bilateral, extent of debridement vs dilation) are necessary given the individual's anatomy, symptoms, prior treatments, and imaging findings.

Billing Rule

BOD billing when used during FESS

When balloon ostial dilation (BOD) is performed concomitantly with FESS, BOD that is integral to the FESS procedure in the same sinus is not separately reportable. If balloon dilation is used as an adjunct on different sinuses during the same operation, follow coding guidance for adjunct procedures and document which sinuses were treated by each technique.

BOD integral to FESS in same sinus is not separately reportable.
When BOD is performed on different sinuses during the same operative session, document and code according to adjunctive procedure rules.
Ensure operative report details which sinuses were treated with FESS versus balloon dilation.

Denial Risk

Inappropriate indications for balloon dilation

Balloon dilation is not appropriate for certain indications. Examples of scenarios likely to be denied include absence of symptoms with only incidental CT findings, positive CT without corresponding clinical CRS/RARS criteria, and headache or sleep apnea as the sole indication without objective evidence of CRS/RARS. Providers should ensure clinical symptoms, duration, prior medical therapy, and objective findings are aligned with the indication.

No symptoms but incidental positive CT — likely not medically necessary.
Headache or sleep apnea alone without CRS/RARS diagnostic criteria or objective sinus disease — likely not medically necessary.
Positive CT findings without corresponding clinical criteria or documentation of failed medical therapy — denial risk.

Billing Rule

Site of service criteria and effective dates

Site-of-service medical necessity review applies to elective sinus surgeries; see policy effective dates for when criteria apply. Note that the Site-of-Service review does NOT apply to Indian Health Services (IHS) facilities. Providers must also follow the policy's Documentation Requirements table and any effective date specifications in coding/billing guidance.

Site-of-service review effective starting 2026-05-01 for applicable procedures.
Site-of-service review does not apply to IHS facilities (see policy note).
Follow Documentation Requirements table referenced in the policy for specific documentation elements and dates.

Documentation Required

Follow policy documentation requirements

Providers must follow the Documentation Requirements table in the policy for all preoperative and operative documentation. Ensure operative reports include explicit justification for surgical extent (which sinuses, unilateral vs bilateral, and techniques used), correlation with symptoms and imaging, prior medical therapy, and any perioperative considerations that affect site of service.

Follow Documentation Requirements table referenced in policy.
Operative report must include surgical extent justification tied to symptoms, imaging, prior treatments, and anatomy.
Include perioperative risk factors that influenced site-of-service selection.