CPT code 01522: Anesthesia for venous thrombectomy of the lower leg

Key Takeaways

CPT code 01522 describes anesthesia for a venous thrombectomy of the lower leg – direct or catheter-based clot removal from a deep vein – a distinct, narrower procedure from CPT 01520, the general not-otherwise-specified (NOS) code for lower leg vein procedures

Reimbursement uses the standard anesthesia formula: (Base Units + Time Units + Qualifying Circumstances) x Conversion Factor – missing any component creates underpayment or denial

Always append a valid anesthesia modifier (AA, QZ, QK, QX, or QY) – omitting the modifier is the single most common reason anesthesia claims for 01522 are denied

Practice management software like Pabau tracks CPT codes, modifiers, and time documentation so anesthesia billing teams submit cleaner claims and resolve denials faster

CPT code 01522 covers anesthesia for a venous thrombectomy of the lower leg – the surgical removal of a blood clot (thrombus) from a deep vein below the knee, performed either directly through an open venotomy or with a catheter-based technique.

It is one of two vein-specific anesthesia codes in the lower leg range: CPT 01520 covers lower leg vein procedures that are not otherwise specified (NOS), while 01522 is reserved specifically for venous thrombectomy.

The code was established by the American Medical Association (AMA), which maintains the CPT code set and assigns base unit values to each anesthesia code.

Billers and anesthesia providers use CPT code 01522 specifically when a patient undergoes a venous thrombectomy of the lower leg – removal of a thrombus obstructing a deep vein, most often to treat an acute deep vein thrombosis (DVT) or thrombophlebitis.

Because the code is limited to this single procedure type, it’s billed far less often than the broader NOS vein code in the same anesthesia range. Like other anesthesia CPT codes, such as 00562, correctly billing 01522 depends on base units, time tracking, modifiers, and paired diagnosis codes.

CPT code 01522 base units and the anesthesia billing formula

Anesthesia reimbursement doesn’t follow a simple flat-fee model. Every claim uses the formula (Base Units + Time Units + Qualifying Circumstance Units) x Conversion Factor = Reimbursement. Understanding each component is essential before submitting a claim for CPT code 01522.

Base units

The American Society of Anesthesiologists (ASA) assigns a base unit value to every anesthesia CPT code through its Relative Value Guide. These base units reflect the complexity of the procedure.

For CPT code 01522, the ASA base unit value is 5 base units – two units higher than CPT 01520 (3 base units), the general NOS code for lower leg vein procedures, reflecting the added complexity of a venous thrombectomy compared with a non-specific vein procedure. Always verify against the current ASA Relative Value Guide, since base unit values are periodically reviewed.

Other anesthesia codes carry entirely different values – 00561, for example, sits in its own base-unit tier altogether, reflecting a different procedure and a different level of complexity.

Time units

Time units are calculated from the documented anesthesia start time to the documented stop time. Most payers, including Medicare, calculate one time unit per 15 minutes of anesthesia. A 45-minute case generates 3 time units. Accurate start/stop time documentation in the anesthesia record is mandatory – missing or ambiguous time entries are a leading cause of claim audits and partial denials.

Qualifying circumstances

Qualifying circumstance codes add units to the formula when certain conditions increase the complexity of anesthesia care, and the unit value differs by code:

• 99100 – extreme age, younger than 1 or older than 70, adds 1 unit
• 99140 – emergency conditions add 2 units
• 99135 – controlled hypotension adds 5 units

These values come from the ASA Relative Value Guide and CMS. Not every 01522 case will have a qualifying circumstance – only append one of these codes when clinical documentation supports it.

Conversion factor

The conversion factor (CF) translates total anesthesia units into a dollar amount. The Centers for Medicare and Medicaid Services (CMS) publishes an anesthesia-specific conversion factor annually.

For 2026, consult the CMS Physician Fee Schedule directly for the current Medicare anesthesia CF, as commercial payers negotiate their own rates and may use different CF values.

The CF varies by Medicare Administrative Contractor (MAC) region, so the same total unit count produces different dollar amounts in different states.

Worked example: A 60-minute venous thrombectomy of the lower leg performed under general anesthesia, with no qualifying circumstances, gives you (5 base + 4 time + 0 QC) x CF = 9 x CF. At a hypothetical CF of $25.00, that yields $225.00 before any geographic adjustments.

The dollar amount will differ – use the FastRVU 2026 RVU lookup tool or the CMS fee schedule to check current rates for your MAC region.

CPT code 01522 reimbursement rates and fee schedule 2026

Reimbursement for CPT code 01522 is never a single national figure. Three variables shift the final payment: the payer type (Medicare, Medicaid, or commercial), the MAC region for Medicare claims, and any geographic practice cost index (GPCI) adjustments that CMS applies.

Regional variation isn’t unique to 01522 – 00352 shows the same MAC-driven spread elsewhere in the anesthesia code family, with a claim in a high-cost urban jurisdiction sometimes reimbursing 15-25% more than the same claim in a rural one.

Medicare reimbursement for CPT code 01522

Medicare pays for anesthesia services using a unit-based formula rather than a set fee per code. CMS sets a national anesthesia conversion factor updated each January. The MAC processes the claim and applies any local GPCI adjustments before paying.

Because the CF and GPCI change annually, any dollar figure from prior-year fee schedules may understate or overstate current Medicare payments. Always verify against the current CMS Physician Fee Schedule before quoting a rate to providers or patients.

Medicare also distinguishes between a physician anesthesiologist billing independently (modifier AA) and a CRNA billing under medical direction (modifiers QK/QX).

The modifier choice affects both the allowed amount and the percentage of the fee schedule that Medicare will pay – typically 100% for AA and 50% each for QK and QX in a medically directed arrangement. Using the wrong modifier is a compliance risk that can attract OIG scrutiny.

Modifiers for CPT code 01522

Every anesthesia claim requires a modifier identifying the type of anesthesia provider and the supervision arrangement. Submitting CPT code 01522 without a modifier will result in an automatic denial from most payers. The five core anesthesia modifiers are listed below.

Medical direction rules (QK/QX/QY) require the supervising physician to meet specific CMS requirements: performing the pre-anesthesia evaluation, being present for induction and emergence, and remaining immediately available throughout.

Failure to document compliance with all seven CMS medical direction criteria can convert a legitimate QK claim into an improper billing – a risk the Office of Inspector General (OIG) actively monitors. For broader guidance on HIPAA compliance in clinical documentation, see our compliance guide.

ICD-10 codes that pair with CPT code 01522

Anesthesia claims require a supporting diagnosis code that justifies the procedure. The ICD-10-CM code must reflect the clinical condition being treated surgically, not the anesthesia itself. Because CPT 01522 is specific to venous thrombectomy, the paired diagnosis should document a thrombotic or thrombophlebitic condition of the deep veins – not an orthopedic, soft-tissue, or dermatologic diagnosis.

Below are common diagnosis codes that pair with CPT code 01522. This list is not exhaustive – the code must accurately reflect the documented diagnosis, ideally confirmed by imaging of the affected vein before the procedure is scheduled.

Always use the most specific ICD-10-CM code available. A vague or unspecified code increases the risk of a medical necessity denial. The AAPC Codify CPT lookup tool includes ICD-10 crosswalk functionality that helps billers identify clinically appropriate diagnosis pairings for specific procedure codes.

CPT 01520 vs CPT 01522: Key differences

CPT 01520 and CPT 01522 are often confused because they share the same anatomical region – the veins of the lower leg. Selecting the wrong code affects both reimbursement and audit risk. The difference is procedural specificity, not anatomy: 01520 is the NOS code for general vein procedures, while 01522 applies only to venous thrombectomy.

This distinction matters most for surgical and vascular practices, including those running on plastic surgery EMR systems, where a single vein-procedure list might include both types of cases.

01522 is not a general catch-all – it applies only when the documented procedure is a venous thrombectomy. If the operative note describes a different vein procedure on the lower leg with no other dedicated code, 01520 (the NOS code) is the correct choice, not 01522.

Billing 01522 for a non-thrombectomy vein procedure is an up-coding risk that can trigger a payer audit. A preoperative CPT 93971 duplex scan documenting the thrombus location is typically part of the medical record that justifies 01522 over 01520.

Documentation requirements for billing CPT code 01522

Clean anesthesia claims depend on complete documentation. Payers audit anesthesia records closely because time-unit billing creates opportunities for overbilling – intentional or not. Every 01522 claim should be supported by documentation covering all of the following elements.

• Pre-anesthesia evaluation: Completed and documented before the procedure begins – includes ASA physical status classification, airway assessment, medication review, and patient history. Required for medical direction compliance under CMS rules.
• Anesthesia start and stop times: Recorded in minutes on the anesthesia record. Start time is when the anesthesiologist or CRNA begins preparing the patient, not when the surgeon begins the procedure. Stop time is when the patient is transferred from anesthesia care.
• Intraoperative monitoring record: Vital signs, medications administered, and any adverse events documented at regular intervals throughout the case.
• Provider qualifications and modifier justification: The record must support whichever modifier is billed. For QK/QX/QY, document that all seven CMS medical direction criteria were met.
• Post-anesthesia note: A brief note confirming the patient’s status at the end of anesthesia care and any post-procedure instructions.
• Qualifying circumstance documentation (if applicable): Clinical evidence supporting any 99100, 99135, or 99140 code appended to the claim.

Keeping medical documentation at your practice organized and accessible is essential for both billing accuracy and audit readiness.

A HIPAA compliance checklist can help anesthesia teams confirm records are audit-ready before submission.

Common billing errors and denial reasons for CPT code 01522

Most anesthesia claim denials are preventable. Billing teams that understand the pattern behind 01522 denials can implement pre-submission checks that cut rejection rates significantly.

This applies whether the anesthesia group supports a hospital-based surgical service or a private practice referring patients out for vascular procedures. These are the failure points that come up most often.

• Missing modifier: Submitting 01522 without AA, QZ, QK, QX, or QY causes an automatic denial from virtually every payer. This is the single most common error in anesthesia billing.
• Incorrect time unit calculation: Rounding anesthesia minutes up rather than down, or using start/stop times from the surgical record instead of the anesthesia record, inflates time units and creates an overpayment risk.
• ICD-10 mismatch: Pairing a diagnosis code that doesn’t support a venous thrombectomy – such as an orthopedic fracture or soft-tissue diagnosis instead of a deep vein thrombosis or thrombophlebitis code – triggers medical necessity denials.
• Unsupported qualifying circumstances: Appending 99100 (extreme age) or 99140 (emergency) without clinical documentation to support the designation. Payers audit QC units closely.
• Medical direction criteria failure: Billing QK or QX when the supervising physician cannot demonstrate compliance with all seven CMS medical direction criteria. This is one of the most common OIG audit triggers for anesthesia groups.
• Confusing 01522 with the NOS code 01520: 01522 applies only to venous thrombectomy. If the operative report describes a different vein procedure with no dedicated code, 01520 (not otherwise specified) is correct – defaulting to 01522 for non-thrombectomy vein work is an up-coding risk.

Practices managing high volumes of medical billing compliance checks often benefit from workflow tools that flag missing modifiers and incomplete documentation before claims go out.

Pabau’s claims management software supports CPT code tracking, modifier assignment, and pre-submission documentation review, helping anesthesia billing teams catch errors at the point of entry rather than after a denial – especially valuable for teams handling multiple procedure code sets across specialties.

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Conclusion

CPT code 01522 is a narrowly defined anesthesia code – reserved specifically for venous thrombectomy of the lower leg – but that specificity creates its own billing risk: confusing it with the broader NOS code 01520, or pairing it with a diagnosis that doesn’t support a thrombectomy.

The most common failure points – wrong code selection, missing modifiers, and unsupported qualifying circumstances – are all addressable through consistent pre-submission review.

Practices that build structured documentation workflows around the anesthesia record catch these errors before they become denials. Pabau’s automated workflow tools flag missing modifiers and incomplete documentation before a claim goes out. To see how it works for anesthesia billing teams, book a demo.

Continue your research

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