🩸 CPT 37799 — Unlisted Procedure, Vascular Surgery
Quick Reference
wRVU: 0.00 — Not CMS-assigned; MAC-priced individually per claim | Global Period: ZZZ (No independent global period — follows comparable code submitted with claim) | Assistant Payable: MAC-determined | Bilateral Indicator: 0
📋 Clinical Description
CPT 37799 is the unlisted procedure code for vascular surgery — the final and catch-all code in the CPT Arteries and Veins surgical range (34001-37799), maintained by the AMA to provide a compliant reporting vehicle when a vascular surgical procedure has been performed that is not accurately described by any existing Category I or Category III CPT code. Use of 37799 is a compliance requirement in those circumstances, not a shortcut; using an existing code that merely approximates the procedure when no accurate match exists constitutes improper code assignment. Because the code carries no fixed descriptor, RVU, or global period, reimbursement is determined case-by-case by the applicable MAC based on the comparable listed CPT code submitted with every claim.
Current procedures commonly submitted under 37799 include intravascular lithotripsy (IVL) of peripheral arteries without concurrent angioplasty, stab phlebectomy with fewer than 10 incisions, arteriovenous malformation (AVM) excision not captured by an existing vascular family, fibrin sheath disruption via existing catheter access without exchange, complex multibranched endovascular repair variants such as TAMBE (Thoracoabdominal Multibranch Endograft), and percutaneous arteriovenous fistula creation where G2170 is not applicable. In each case, the Society for Vascular Surgery and AMA direct physician reporting to **37799**with a concurrent narrative and comparable code.
This code may be reported in the following clinical contexts:
- Intravascular Lithotripsy (IVL) — Peripheral Arteries Without Angioplasty — When IVL is performed on a lower extremity artery as a standalone intervention; physicians report 37799(not facility codes C9764-C9767) and compare to 37246 for MAC valuation.
- Stab Phlebectomy — Fewer Than 10 Incisions — CPT describes phlebectomy at 37765 (10-20 incisions) and 37766 (>20 incisions); when documentation specifies fewer than 10 incisions, 37799 is the only appropriate code, compared to 37765 for pricing reference.
- Arteriovenous Malformation Excision — Peripheral Vessel — AVM excision not captured by a dedicated CPT code is reported as **37799**and compared to 37607 (ligation of arteriovenous fistula or aneurysm) for valuation.
- Fibrin Sheath Disruption via Existing Catheter Access — When fibrin sheath is mechanically disrupted through existing access without a separately coded catheter exchange; 37799 is reported and compared to 37209 (exchange/repositioning of transluminal catheter) for MAC pricing.
- Complex Multibranched Endovascular Repair (TAMBE) — For thoracoabdominal multibranch endograft procedures with no matching fenestrated/branched CPT descriptor; comparable code drawn from the 34841-34848 family for valuation reference.
🔬 Submission Framework & Documentation Requirements
⚠️ Unlike all other CPT codes in this range, **37799**does not describe a discrete procedure. The table below summarizes required submission components and how each drives adjudication.
| Submission Component | Required Content | Impact on Adjudication |
|---|---|---|
| Operative Report | Step-by-step technique, access site, target vessel(s), devices used, fluoroscopic or imaging guidance, and final clinical findings | Primary basis for medical necessity; a human MAC reviewer replaces automated adjudication for every 37799 claim |
| Comparable CPT Code | The most analogous listed Category I code cited in Box 19 (CMS-1500) or electronic equivalent — submitted for valuation only, never billed | Determines MAC payment benchmark; selection directly impacts reimbursement level and appeal outcome |
| Medical Necessity Statement | Explains why no existing CPT code accurately describes the procedure; includes clinical indication and, for novel techniques, supporting peer-reviewed literature | Absence is the leading cause of denial; required by all payers including Medicare MACs, Wisconsin Medicaid, BCBS of WI, UMR, UHC, Cigna, and Aetna |
| Prior Authorization | Obtained before the procedure where payer requires it | Most payers require PA for unlisted codes; failure to obtain PA results in non-appealable denials at many payers |
| Box 19 / Electronic Narrative | Short procedure descriptor plus comparable code reference | Required for electronic claim processing; absence triggers automatic denial from most clearinghouses and MACs |
Clinical Pearl
The leading cause of 37799 denial is not clinical — it is documentation. A MAC reviewer, not an automated system, reads every claim, and what they find in the record determines payment. The operative note, medical necessity letter, and comparable code must be assembled before claim submission, and before the procedure when PA is required. When appealing a denial, include a narrative explaining specifically how the procedure differs from existing CPT codes; submitting only the operative report without an explanatory narrative significantly reduces appeal success rates. Track historical MAC payments for each specific procedure type reported under 37799 to build an internal reimbursement benchmark.
✅ Submission Includes / Required Documentation
- Complete operative report with step-by-step procedural description, access site, target vessel, imaging guidance used, technique, and all devices or implants
- Medical necessity statement explaining why no Category I or Category III CPT code accurately describes the service performed
- Comparable listed CPT code identified for MAC pricing reference — cited in Box 19, not separately billed
- Supporting clinical or specialty society literature for novel or emerging techniques (IVL, TAMBE, percutaneous AVF)
- Prior authorization documentation where required by payer (Medicare MACs for designated procedures, Wisconsin Medicaid, and most commercial payers)
- Box 19 or equivalent electronic narrative field completed with procedure descriptor and comparable code reference
- Standard pre-procedure evaluation, post-procedure care instructions, and device/implant documentation as applicable
❌ Excludes / Do Not Report Together
| Code | Description | Relationship to 37799 |
|---|---|---|
| 37765 | Stab phlebectomy of varicose veins, one extremity; 10-20 incisions | Use 37765 when exactly 10-20 incisions are documented; 37799 is appropriate only for <10 incisions — once a specific code accurately describes the service, 37799 is not reportable |
| 37766 | Stab phlebectomy, >20 incisions | Use 37766 when more than 20 incisions are documented; same principle applies — a specific code supersedes 37799 |
| 37246 | Transluminal balloon angioplasty, non-coronary | When IVL is performed with concurrent angioplasty, 37246 is reported for the angioplasty component; 37799 covers the IVL only when no angioplasty is performed — the two may be reported together when both services are independently documented |
| 37209 | Exchange of a previously placed intravascular catheter | If a catheter exchange is performed, 37209 is the correct code and 37799 does not apply; 37799 is appropriate only when sheath disruption occurs without catheter removal and replacement |
| Category III codes (C-codes) | e.g., C9764-C9767 for IVL (facility) | Category III codes take precedence over unlisted codes per AMA guidance; C-codes are facility-side only — 37799 remains the physician profee code for IVL; review AMA Category III updates annually as procedures may gain permanent Category I codes |
| E/M codes (992xx) | Office visit, any level | Separately reportable only when modifier -25 is appended to the E/M code, documenting a significant, separately identifiable evaluation beyond the routine pre-procedure assessment |
Bundling Alert — Global Period is ZZZ, Not 000/010/090
CMS does not independently assign a global period to 37799; the MAC assigns a global period based on the comparable code submitted. If the comparable code carries a 90-day global (e.g., 37780 or 37785), follow-up visits within that window may be considered bundled. Document the comparable code at time of service and track the applicable global window accordingly. The most common audit finding for unlisted vascular code submissions is billing post-procedure E/M visits during the comparable code’s global window without modifier -24 (unrelated E/M during global period) when the visit is unrelated to the procedure. When the visit is related to the procedure, it is bundled and not separately reportable.
🌳 Code Tree — Surgery: Arteries and Veins
CPT 34001-37799 Surgery: Arteries and Veins
│
├── 34001-34530 Embolectomy / Thrombectomy
│
├── 35001-35907 Direct Repair of Aneurysm / Blood Vessel
│
├── 35301-35390 Thromboendarterectomy
│
├── 35450-35476 Transluminal Angioplasty (Open)
│
├── 35500-35907 Bypass Graft
│
├── 36000-36598 Vascular Access and Injection Procedures
│
├── 36800-36870 Hemodialysis Access
│
├── 37140-37216 Vascular Ligation, Transposition, and Intracranial Procedures
│
├── 37220-37239 Revascularization — Lower Extremity Arteries
│
├── 37241-37244 Vascular Embolization and Occlusion
│
├── 37246-37249 Transluminal Balloon Angioplasty (Endovascular)
│
├── 37252-37253 Intravascular Ultrasound (IVUS)
│
├── 37500-37501 Endoscopy — Vascular
│
├── 37600-37660 Ligation — Major Vessels
│
├── 37700-37785 Varicose Veins
│ ├── 37760 Ligation, perforator veins, subfascial, radical (Linton type)
│ ├── 37761 Ligation, perforator vein(s), subfascial, open
│ ├── 37765 Stab phlebectomy, 10-20 incisions (Global: 010)
│ ├── 37766 Stab phlebectomy, >20 incisions (Global: 010)
│ ├── 37780 Ligation and division, short saphenous vein (Global: 090)
│ └── 37785 Ligation, division, excision of varicose vein cluster (Global: 090)
│
└── ▶▶ 37799 ◀◀ Unlisted procedure, vascular surgery ← YOU ARE HERE (Global: ZZZ — MAC-assigned)
💰 RVU & Reimbursement Profile
| Component | Value |
|---|---|
| Work RVU (wRVU) | 0.00 — Not independently assigned by CMS (MAC prices each claim individually based on the comparable code submitted; no MPFS line exists for 37799) |
| Global Period | ZZZ — No independent global period; MAC assigns based on comparable code |
| Bilateral Indicator | 0 — No CMS bilateral rule assigned; bilateral determination made by MAC based on actual procedure and comparable code |
| Assistant Surgeon | MAC-determined on a per-claim basis |
| Co-Surgeon | MAC-determined |
| Team Surgery | MAC-determined |
| PC/TC Split | ❌ No — Procedure code only (Indicator 0) |
| Modifier -51 Exempt | No — standard multiple procedure rules apply when applicable |
| Anesthesia | Variable — depends on actual procedure; ranges from local infiltration to general anesthesia; separately billable under applicable anesthesia code |
Reimbursement Strategy
Payment for 37799 is entirely dependent on (1) documentation package quality and (2) comparable code selection. A comparable code that underrepresents the procedure’s complexity undersells the work; a comparable code that overstates it risks denial or recoupment. Build an internal tracking log of what WPS (Wisconsin MAC) and payer-specific MACs have paid historically for each procedure type reported under 37799 and appeal aggressively when initial payments fall below the comparable code benchmark. Wisconsin Medicaid and BCBS of WI payer policies on unlisted code submission requirements may differ from Medicare MAC policy — confirm payer-specific Box 19 and PA requirements before billing each payer the first time.
🏷️ Modifier Reference
| Modifier | Name | When to Apply |
|---|---|---|
| -RT | Right Side | Procedure performed on a right-sided vessel; append to 37799 for laterality documentation |
| -LT | Left Side | Procedure performed on a left-sided vessel |
| -50 | Bilateral Procedure | Same procedure performed on bilateral vessels in the same session; confirm MAC-specific format preference (single line -50 vs. two lines -RT/-LT) before submitting — WPS has specific bilateral unlisted code guidance |
| -59 | Distinct Procedural Service | When 37799 is reported alongside another vascular code and payer inappropriately bundles them; distinguishes separate vessel, separate approach, or independent clinical service |
| -51 | Multiple Procedures | When 37799 is reported alongside other surgical procedures in the same session; apply to the lower-valued code |
| -25 | Significant, Separately Identifiable E/M | Applied to the E/M code — not 37799 — when a separately documented office visit is performed on the same date; documentation must support an evaluation beyond the pre-procedure assessment |
| -24 | Unrelated E/M During Postoperative Period | Applied to the E/M code when a patient is seen during the comparable code’s global window for a condition unrelated to the procedure; document unrelated nature explicitly |
| -76 | Repeat Procedure by Same Physician | When the same unlisted vascular procedure is repeated within the same session |
| -80 | Assistant Surgeon | When an assistant surgeon participates; payability is MAC-determined for unlisted codes |
⚠️ AMA CPT 2024 Modifier Restriction: Modifiers -22 (Increased Procedural Services), -52 (Reduced Services), and -53 (Discontinued Procedure) are not used with unlisted codes. Because unlisted codes have no assigned description, there is no defined service against which to measure a reduction, increase, or discontinuation. If the procedure was partially performed or discontinued, document this thoroughly in the operative report and narrative; do not append -52 or -53 to 37799. This is a known audit finding.
🩺 Common ICD-10-CM Pairings
Peripheral Arterial Disease — IVL / Arterial Intervention Context
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| I70.201 | Unspecified atherosclerosis of native arteries of extremities, right leg | ✅ HCC — peripheral vascular disease | Confirm native vs. bypass graft vessel; unspecified subtype — query for rest pain, claudication, or ulceration to capture higher specificity I70.21x/I70.22x codes |
| I70.202 | Unspecified atherosclerosis of native arteries of extremities, left leg | ✅ HCC | Left-side counterpart; avoid I70.209 (unspecified leg) when laterality is documented anywhere in the record |
| I70.209 | Unspecified atherosclerosis of native arteries of extremities, unspecified leg | ✅ HCC | Use only when laterality is entirely absent from documentation; query provider before defaulting here |
Varicose Veins — Stab Phlebectomy (<10 Incisions) Context
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| I83.90 | Asymptomatic varicose veins of unspecified lower extremity | ❌ No | Medical necessity scrutiny is highest here; document symptom burden, failed conservative management, and functional impact explicitly to support payer coverage |
| I83.10 | Varicose veins of unspecified lower extremity with inflammation | ❌ No | Strengthens medical necessity narrative; provider must explicitly document inflammation — do not infer |
| I83.009 | Varicose veins of unspecified lower extremity with ulcer of unspecified site | ❌ No | Highest medical necessity support in this grouping; query for ulcer site and laterality to reach a more specific code when documentation supports it |
Arteriovenous Malformation Context
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| Q27.30 | Arteriovenous malformation, site unspecified | ❌ No | Query for site specificity when AVM location is documented elsewhere in the chart — unspecified is appropriate only when documentation truly does not identify the site |
| Q27.39 | Arteriovenous malformation of other site | ❌ No | Use for peripheral vascular AVM at a site other than the digestive system (Q27.33); confirm site from operative/imaging documentation |
| I77.4 | Celiac artery compression syndrome | ❌ No | Median arcuate ligament syndrome (MALS); report when the procedure specifically addresses celiac axis compression — operator documentation must name the condition |
Device / Complication Context — Fibrin Sheath, Complex Repair
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| T82.898A | Other specified complication of vascular prosthetic devices, implants and grafts, initial encounter | ❌ No | Use for fibrin sheath disruption on tunneled catheter or TAMBE-related device complication; confirm initial vs. subsequent encounter (A vs. D); the 7th character is mandatory |
| I72.4 | Aneurysm of artery of lower extremity | ❌ No | Use for complex peripheral aneurysm repairs without a specific CPT equivalent; confirm that no code in the 35001-35152 or 34001-34530 range accurately describes the procedure before selecting 37799 |
Comorbidity / Supporting Codes (ESRD / Dialysis Context)
| ICD-10 Code | Description | HCC? | Clinical Notes |
|---|---|---|---|
| N18.6 | End-stage renal disease | ✅ HCC 136 | Report as additional code when fibrin sheath or dialysis access procedure is the basis for 37799; supports clinical picture and medical necessity |
| Z99.2 | Dependence on renal dialysis | ❌ No | Report with N18.6 in ESRD / dialysis access context to fully document dialysis dependence per ICD-10-CM Official Guidelines |
Coding Specificity Reminder
The unlisted nature of 37799 does not reduce the ICD-10-CM specificity obligation. MAC reviewers read the CPT code, the Box 19 narrative, and the ICD-10-CM codes as a coherent clinical story; vague or parent-level diagnosis codes actively undermine the medical necessity argument and increase denial risk. The three specificity axes most frequently missed in vascular coding are laterality, condition type (native artery vs. bypass graft vessel vs. venous structure), and encounter type (initial vs. subsequent). Query-first standard applies regardless of how routine the submission appears.
🏥 MS-DRG Considerations (Inpatient)
Inpatient Coding Reminder
CPT 37799 is a physician profee code with no independent DRG impact. Inpatient DRG assignment is driven entirely by the ICD-10-PCS code(s) assigned by the facility coder for the actual vascular procedure performed. When the admission is driven by a vascular procedure reported under 37799, grouping falls within MDC 05 — Diseases and Disorders of the Circulatory System; the specific DRG (e.g., DRG 252-254 for peripheral vascular disorders; DRG 237-238 for major cardiovascular procedures) is determined by PCS root operation, body part coded, and CC/MCC tier. Physician coders reporting 37799 should coordinate with facility coding to ensure clinical documentation supports the highest-specificity ICD-10-PCS selection for DRG optimization. CDI query opportunities are significant for complex procedures like TAMBE, where the PCS root operation selection (Restriction vs. Repair vs. Supplement) meaningfully affects DRG weight, and documentation must name the technique with sufficient precision for facility coders to make a defensible root operation determination.
🔧 ICD-10-PCS Equivalents (Inpatient Facility Coding)
Note
Because 37799 reports a variable procedure, the ICD-10-PCS codes below are representative examples organized by the most common procedure types submitted under 37799. Facility coders must assign PCS codes based on the actual documented procedure — the CPT code does not drive PCS selection. This table provides a root operation framework; it is not exhaustive.
| PCS Code | Full Description | Procedure Context |
|---|---|---|
04CK3ZZ | Extirpation, Femoral Artery, Right, Percutaneous, No Device, No Qualifier | IVL — right femoral / superficial femoral artery |
04CL3ZZ | Extirpation, Femoral Artery, Left, Percutaneous, No Device, No Qualifier | IVL — left femoral / superficial femoral artery |
06BQ0ZZ | Excision, Greater Saphenous Vein, Right, Open, No Device, No Qualifier | Stab phlebectomy <10 incisions, right leg |
06BR0ZZ | Excision, Greater Saphenous Vein, Left, Open, No Device, No Qualifier | Stab phlebectomy <10 incisions, left leg |
04BE0ZZ | Excision, Internal Iliac Artery, Right, Open, No Device, No Qualifier | AVM excision — right internal iliac / hypogastric artery |
04BF0ZZ | Excision, Internal Iliac Artery, Left, Open, No Device, No Qualifier | AVM excision — left internal iliac artery |
PCS Character Analysis — 04CK3ZZ (IVL — Right Femoral Artery, Representative Example)
| Position | Character | Value | Definition |
|---|---|---|---|
| 1 | Section | 0 | Medical and Surgical |
| 2 | Body System | 4 | Lower Arteries |
| 3 | Root Operation | C | Extirpation (taking or cutting out solid matter from a body part — applies to IVL where calcified plaque is fractured and removed from the arterial wall) |
| 4 | Body Part | K | Femoral Artery, Right |
| 5 | Approach | 3 | Percutaneous |
| 6 | Device | Z | No Device |
| 7 | Qualifier | Z | No Qualifier |
PCS Root Operation: Extirpation (C) vs. Dilation (7) vs. Excision (B)
- Use Extirpation (C) when the primary objective is removing solid matter (calcium, thrombus, fibrin sheath) from within the vessel — the standard root operation for standalone IVL and fibrin sheath disruption
- Use Dilation (7) when the primary objective is expanding a narrowed vessel lumen — applies to angioplasty; when IVL and angioplasty are performed together, Dilation with an intraluminal device qualifier may be the correct root operation and a separate 37799 may not apply
- Use Excision (B) when a portion of a vessel wall or attached structure (AVM, venous cluster, aneurysm segment) is surgically removed — the correct root operation for AVM excision and stab phlebectomy
- When bilateral vessels are treated, assign separate PCS codes for each side — ICD-10-PCS has no modifier equivalent for bilateral procedures; bilateral CPT -50 does not translate to a single PCS code
📝 Coding Examples
Example 1 — Outpatient Hospital: IVL of Left Superficial Femoral Artery, No Concurrent Angioplasty
Clinical Scenario: A 71-year-old male with documented peripheral arterial disease presents for intravascular lithotripsy of the left superficial femoral artery. The operative note documents percutaneous access via the left common femoral artery, fluoroscopic guidance, IVL catheter positioning at a calcified SFA lesion, delivery of multiple lithotripsy pulses, and completion angiography showing improved lumen diameter. The note explicitly states no balloon was deployed and no angioplasty was performed. No separately documented E/M service is present for this date.
| Field | Code | Rationale |
|---|---|---|
| CPT | 37799-LT | Unlisted vascular procedure — IVL of peripheral artery without concurrent angioplasty; -LT for left-sided intervention; comparable code 37246 cited in Box 19 for MAC valuation only |
| PDx | I70.202 | Atherosclerosis of native arteries of extremities, left leg — most specific code reflecting PAD driving IVL; query for rest pain or ulceration to capture higher-specificity subtype |
Note
SVS guidance explicitly directs physicians to report 37799 for peripheral IVL, not the facility-side C9764-C9767 codes. The comparable code 37246 is cited for pricing reference in Box 19 and is never separately billed. Fluoroscopic guidance is bundled into the IVL work and is not separately reportable.
Example 2 — Outpatient Hospital: Stab Phlebectomy With 7 Incisions, Right Leg, With Separately Documented E/M
Clinical Scenario: A 58-year-old female with symptomatic varicose veins of the right lower extremity presents for stab phlebectomy. The operative note specifies 7 stab incisions along tributary vessels of the great saphenous vein, right leg; tributaries were avulsed and removed through micro-incisions. A separately documented E/M was performed at the same visit addressing bilateral lower extremity edema and right calf pain not related to the varicose vein procedure and documented distinctly from the pre-operative phlebectomy assessment, with its own history, exam, and medical decision-making.
| Field | Code | Rationale |
|---|---|---|
| CPT 1 | 99213-25 | Separately documented E/M for bilateral edema and calf pain evaluation — -25 modifier on the E/M code, not on 37799 |
| CPT 2 | 37799-RT-51 | Unlisted vascular — stab phlebectomy <10 incisions, right leg; -RT for laterality; -51 for multiple procedures in same session; comparable code 37765 cited in Box 19 |
| PDx | I83.90 | Varicose veins of unspecified lower extremity, asymptomatic — primary indication for phlebectomy; document failed conservative management to support medical necessity |
Warning
Modifier -25 belongs on the E/M code (99213), not on 37799. A phlebectomy’s pre-procedure assessment is bundled into the procedure’s payment; the E/M is separately reportable only because the documented complaint (bilateral edema, calf pain) was clinically distinct and independently and completely documented with its own history, exam, and MDM. If documentation does not clearly separate these services, -25 is not defensible and the E/M is not separately billable.
Example 3 — Inpatient: Fibrin Sheath Disruption via Existing Dialysis Catheter, No Catheter Exchange
Clinical Scenario: A 63-year-old male with ESRD on hemodialysis is admitted with a malfunctioning right internal jugular tunneled dialysis catheter due to fibrin sheath formation confirmed on fluoroscopy. The operative report documents percutaneous access via the existing catheter, fluoroscopic confirmation of sheath at the catheter tip, and mechanical disruption using a snare technique. The existing catheter was retained and function was restored; no catheter exchange or removal and replacement was performed. The procedure is not described by any existing CPT code; 37799 is reported with comparable code 37209.
| Field | Code | Rationale |
|---|---|---|
| CPT | 37799 | Unlisted vascular — fibrin sheath disruption via existing access without catheter exchange; comparable code 37209 cited in Box 19; no laterality modifier added as access is central venous |
| PDx | T82.898A | Other specified complication of vascular prosthetic devices, initial encounter — fibrin sheath on tunneled hemodialysis catheter; 7th character A is required for initial encounter |
| SDx | N18.6 | End-stage renal disease — documents clinical context and dialysis dependence; required per ICD-10-CM guidelines when ESRD is documented |
| SDx | Z99.2 | Dependence on renal dialysis — report with N18.6 per Official Guidelines to fully capture dialysis status |
Note
Global period reminder: 37209 (the comparable code) is not separately billed — it is cited for valuation only. If a catheter exchange had been performed rather than sheath disruption alone, 37209 would be the correct billable code and 37799 would not apply. The operative note must unambiguously state that the existing catheter was retained and no exchange was performed to defend 37799 over 37209 on audit.
⚠️ Common Coding Pitfalls
-
Reporting 37799 when a specific Category I or III code exists: This is the most fundamental misuse of the unlisted code and constitutes improper code assignment — a compliance risk equivalent to upcoding. A procedure that closely matches an existing CPT descriptor must use that code, even if the work was more complex or the technique slightly different. AMA guidance is explicit: approximation is not a basis for 37799. When a Category III temporary technology code exists in the facility setting (e.g., C9764-C9767 for IVL), verify whether a physician-specific code also exists before defaulting to 37799; the landscape changes annually as procedures gain permanent Category I status.
-
Submitting 37799 without a comparable CPT code: Every 37799 claim must include a comparable listed CPT code in Box 19 or the electronic equivalent — this is what allows the MAC to price the service. Submitting 37799 without a comparable code results in automatic denial from most MACs and payers. The comparable code is cited for valuation only; billing both 37799 and the comparable code is a separate billing error. Always cite the comparable code in Box 19, not on the claim fee line.
-
Appending modifier -22, -52, or -53 to 37799: Per AMA CPT 2024 guidance, these modifiers are not applicable to unlisted codes because unlisted codes have no assigned description against which to measure a reduction, increase, or discontinuation. This is a known audit finding. If the procedure was partially performed or discontinued, document this in the operative report and submission narrative; do not append these modifiers.
-
Failing to obtain prior authorization when the payer requires it: Most payers — including Medicare MACs for select procedures, Wisconsin Medicaid, BCBS of WI, UMR, UHC, Cigna, and Aetna — require prior authorization for unlisted codes. Submitting 37799 without PA when required results in a denial that cannot be successfully appealed on medical necessity grounds alone. Confirm payer-specific PA requirements before the procedure, not at claim submission.
-
Defaulting to unspecified ICD-10-CM codes without querying: The unlisted nature of 37799 does not reduce the ICD-10-CM specificity requirement. MAC reviewers read the diagnosis codes alongside the CPT and Box 19 narrative as a coherent clinical picture; vague or unspecified diagnosis codes undermine the medical necessity story. Laterality, condition type (native artery vs. graft, type of malformation, ulcer site), and encounter type are the three axes most frequently missed. Query-first standard applies.
-
Failing to track the global window of the comparable code: Because 37799 has no assigned global period, some coders skip global window tracking entirely — this is a billing error. The comparable code submitted for valuation carries its own global period, and MAC adjudication may apply that global to follow-up care. Identify the comparable code’s global period at the time of service, note it in the patient’s account, and apply modifier -24 (unrelated E/M) or -79 (unrelated procedure) as appropriate for services rendered within that window.
📎 Sources
AMA CPT 2026 Professional Edition · CMS 2026 Medicare Physician Fee Schedule Final Rule (CMS-1809-F) · CMS MPFS RVU26A Relative Value Files · NCCI Policy Manual, CMS 2025-2026 · ICD-10-CM Official Guidelines for Coding and Reporting FY2026 · ICD-10-PCS Official Guidelines for Coding and Reporting FY2026 · AMA CPT Assistant, January 2024 — Unlisted Code Guidance and Modifier Applicability Update · Society for Vascular Surgery (SVS) — Coding & Reimbursement: Vascular Coding Q&A, 2024-2025 (vascular.org) · Libman Education — “CPT Coding: The Appropriate Use of Unlisted CPT Codes” (March 2024) · Pabau — “CPT Code 37799: Unlisted Procedure, Vascular Surgery” (April 2026) · WPS Government Health Administrators — Unlisted Procedure Code Submission Requirements, Jurisdiction 5/8 MAC