The 2026 IR Coding Overhaul: What Every Billing Specialist Needs to Know

By Valeriya Nifadeva, Billing Department, WCH

Imagine this: a vascular surgeon completes a complex multi-vessel lower extremity revascularization — technically flawless, clinically successful. The billing team codes it the same way they coded it last year. Come January 2026, the entire claim denies. No appeal will fix it, because the logic itself was wrong.

This is not a hypothetical. It is the near-certain outcome for any practice that enters 2026 without understanding what CPT has fundamentally changed about interventional radiology coding for lower extremity procedures.

What’s Actually Changing — and Why It Matters

The shift from 2025 to 2026 is not a minor update. It is a structural rebuild. The 2025 system organized lower extremity IR codes around vessels: you identified the first vessel treated, assigned a base code, then added add-on codes for each subsequent vessel. Simple, but imprecise — it didn’t account for the fact that treating a stenosis and treating a chronic total occlusion (CTO) are clinically and operationally very different procedures.

The 2026 system corrects this. It is built around lesions and territories. The code set expands from 16 codes to 46. The selection logic now requires coders to work through a five-step decision tree for every territory treated: identify the territory, determine lesion complexity, select the intervention type, apply add-ons, then restart the process for each new territory.

The practical implication: a coder who was excellent in 2025 will produce systematic errors in 2026 if they don’t retrain. The muscle memory is wrong.

The Detail That Will Make or Break Your Claims: Lesion Complexity

Of all the changes, one stands out as the highest-risk documentation gap: lesion complexity.

In 2026, every code selection begins with a binary question — is this a straightforward lesion (stenosis) or a complex lesion (chronic total occlusion, CTO)? The answer determines which family of codes applies, and the difference in reimbursement between the two tiers is significant.

The problem is that physicians don’t always document this distinction explicitly. An operative note might describe a vessel as “occluded” without confirming whether it meets CTO criteria, or use language like “severe stenosis” that sits ambiguously between the two categories.

The rule is simple and non-negotiable: if lesion complexity is not documented, do not code — query first. Defaulting to straightforward when a CTO was actually treated is undercoding. Assuming CTO without documentation is overcoding. Both create compliance risk.

Practices should build a physician query template specifically for this scenario before January 2026. It is one of the most actionable preparation steps available right now.

Territory Logic: The Framework That Ties Everything Together

The four anatomic territories — Iliac, Femoral/Popliteal, Tibial/Peroneal, and Inframalleolar — are not just geographic labels. They are the structural units around which the entire 2026 code set is organized.

Each territory is coded independently. You apply the five-step decision order, select your base code and add-ons, then fully restart the process for the next territory. There is no carry-over logic between territories.

Within territories, the procedural hierarchy determines which code to use when multiple interventions are performed on the same lesion: stent plus atherectomy sits at the top, followed by atherectomy alone, then stent alone, then balloon angioplasty only. The highest intervention performed determines the base code; lower-level interventions at the same lesion are bundled and not separately reported.

One territory deserves special attention: Tibial/Peroneal, which carries a hard cap of three interventions per session — one base code and two add-ons. If four tibial vessels are treated, only the three highest-complexity interventions are reportable. Coders working with complex limb salvage cases need to know this ceiling cold.

What You Were Always Bundling (And Maybe Weren’t)

One of the most consistent sources of audit risk in IR coding — both before and after 2026 — is the separate reporting of services that CPT considers integral to the intervention.

Catheter placement is never separately reportable when performed as part of a lower extremity intervention. Neither is access, roadmapping angiography, or completion angiography. These are bundled by CPT instruction, not by payer policy, which means Modifier 59 cannot unbundle them. Appending Modifier 59 to catheter placement codes in an IR case is not a solution — it is a red flag.

The same logic applies to thrombectomy performed with the same device as the primary intervention. If the physician used the atherectomy catheter to also remove thrombus, that thrombectomy is bundled. If a separate dedicated thrombectomy device was used, the situation warrants a closer review of CPT instructions and payer policy.

Venous Cases: The Good News

Not everything is getting more complex. Venous interventions remain organized around veins — no territory hierarchy, no lesion complexity tiers. The core codes (37238/37239 for stenting, 37248/37249 for balloon dilation) follow straightforward first-vessel and add-on logic. When both angioplasty and stent are performed in the same vein, report only the stent code.

Ablation and sclerotherapy coding is similarly stable: select based on technique (RFA, laser, mechanochemical, adhesive) and whether one or multiple veins were treated. For practices with a significant venous volume, this stability is welcome.

Three Things to Do

1. Audit your operative note templates. Work with your IR physicians now to ensure that notes explicitly document lesion complexity — stenosis versus CTO — for every vessel treated. This is not a documentation preference; it is a coding prerequisite in 2026.

2. Remap your charge capture workflows. Any workflow built around 2025 vessel-based logic needs to be rebuilt. Create territory-based encounter forms that walk through the five-step decision order. Consider building in a mandatory lesion complexity field that cannot be left blank.

3. Run a parallel coding exercise before go-live. Pull a representative sample of 2025 IR cases and recode them using 2026 logic. Compare the results. The gaps you find — in documentation, in coder knowledge, in charge capture design — are exactly the gaps that will produce denials in January if left unaddressed.

The Bigger Picture

The 2026 restructure is a sign that CPT is moving toward greater clinical specificity across high-complexity specialties. Lesion-based coding is more accurate and, when used correctly, better reflects the actual work performed. That is good for the specialty — but only for practices that make the transition successfully.

The practices that will benefit most are those that treat the documentation workflow and the coding workflow as inseparable. When the surgeon writes the operative note and the coder selects the code, they are collaborating on the same claim. The 2026 changes make that collaboration more important, and more consequential, than ever.

Sources

1. American Medical Association. CPT 2026 Professional Edition. AMA Press, 2025.
2. Centers for Medicare & Medicaid Services. Medicare Claims Processing Manual, Chapter 12 — Physicians/Nonphysician Practitioners. CMS.gov.
3. Society of Interventional Radiology. Coding and Reimbursement Resources for Lower Extremity Arterial Interventions. SIR, 2024.
4. American College of Radiology. Interventional Radiology Coding Reference, 2025 Edition. ACR.
5. AAPC. Medical Coding Training: CPC — Cardiovascular and Interventional Radiology Module. AAPC, 2024.
6. Sabilova E. Interventional Radiology Billing & Coding: Lower Extremity Interventions 2025–2026. Webinar, AAPC Tashkent Chapter, February 2026.