CPT Code 73700: Lower extremity CT without contrast billing guide

Key takeaways

CPT Code 73700 covers computed tomography of the lower extremity without contrast material, including the leg, knee, ankle, and foot.

Three codes share that region: 73700 without contrast, 73701 with contrast, and 73702 with and without contrast.

Picking the wrong contrast variant is the top denial driver on lower extremity CT claims.

The 2026 Medicare national average is roughly $130.26, and the facility and non-facility rates match.

Documentation must name the ordering provider, the clinical indication, the medical necessity, and any reason contrast was withheld.

CPT Code 73700 is the billable code for computed tomography of the lower extremity performed without contrast material. It covers the leg, knee, ankle, and foot, and it is reported once per study session. The contrast decision is what separates it from 73701 and 73702, and it is the variable coders get wrong most often.

This guide covers the official descriptor, the clinical indications, the modifier logic, the 2026 Medicare rates, and the ICD-10 codes that support medical necessity. It also shows how one non-contrast CT ends up as a single, correctly modified line on the claim.

What CPT Code 73700 covers

Official descriptor: Computed tomography, lower extremity; without contrast material.

CPT Code 73700 is assigned when a CT scan of the lower extremity runs without any intravenous contrast agent. The AMA CPT code set places it in the Radiology section. It applies to imaging of the leg, knee, ankle, or foot.

The “lower extremity” designation covers the whole limb below the pelvis. The specific area imaged belongs in the clinical record, but it does not change the code you report.

The code is reported once per study session, not once per anatomical sub-region. If both lower extremities are imaged, modifiers LT and RT or modifier 50 apply.

CPT 73700 vs 73701 vs 73702: Choosing the right code

Contrast is the only difference between the three codes. All three describe the same anatomical region, so the acquisition protocol decides which one goes on the claim.

If contrast was planned but withheld for patient factors, the clinical record has to say so. Billing 73700 is still correct in that scenario. The documentation simply needs to explain why contrast was withheld, such as a documented allergy or renal insufficiency.

When non-contrast CT of the lower extremity is appropriate

Non-contrast CT is appropriate whenever the clinical question can be answered without vascular or soft-tissue enhancement. The AAPC CPT code lookup references 73700 across orthopedic, podiatric, and sports medicine settings.

Common appropriate use scenarios include:

• Fracture identification and characterization, including stress fractures and complex fractures with suspected intra-articular extension
• Osteomyelitis assessment when initial X-rays are inconclusive
• Pre-operative planning for orthopedic or podiatric surgery
• Evaluation of bone tumors or cortical lesions where soft-tissue detail is secondary
• Post-surgical hardware assessment, where metal artifact may limit MRI
• Tarsal coalition evaluation in the ankle and foot

Non-contrast is generally preferred when renal function is compromised or a contrast allergy is documented. Some payers require prior authorization for lower extremity CT. Document the clinical indication before the study is ordered, so the request has support behind it.

Choosing the right modifier

Three variables drive modifier selection for 73700: equipment ownership, interpretation, and laterality. Attaching the wrong modifier is one of the most common reasons radiology claims get denied or downcoded.

When the interpreting radiologist and the technical facility are separate entities, both bill 73700. One line carries modifier 26 and the other carries modifier TC. Billing global when a split applies is a compliance risk, so verify the approach against current NCCI edits and payer policy.

Read together, the three decisions produce one coded line rather than three separate choices.

2026 Medicare reimbursement rates for 73700

Medicare payment for 73700 varies by geographic locality. The CMS Physician Fee Schedule lookup tool is the authoritative source for current rates. The figures below are national averages, so confirm your own locality before posting an expected payment.

Unlike most codes on the fee schedule, 73700 carries no facility differential. CMS pays the same national average whether the study happens in a hospital or an independent imaging center. So a facility rate that differs from the non-facility rate in your billing system is a setup error, not a payer rule.

The split between the two components is worth knowing before you reconcile a remittance. The technical component carries roughly 60% of the payment, and the professional component the remaining 40%.

Geographic payment localities move these figures, so check the work, practice expense, and malpractice RVU values that apply to your area. Validating each line against your payer-specific fee schedule catches a stale rate before the claim leaves the practice.

Documentation requirements payers check

Incomplete documentation is the second most common reason 73700 claims are denied. Payers look for specific elements to establish medical necessity, and a missing element can trigger a records request or an outright rejection. Build the record at the point of order, not at the point of submission.

A complete 73700 claim requires documentation of all of the following:

• Ordering provider identity: name, NPI, and relationship to the patient, whether referring or treating
• Clinical indication: the symptom, sign, or finding that prompted the CT order, such as ankle pain with cortical irregularity on X-ray
• Medical necessity: why imaging was required at this point in the patient’s care. A diagnosis alone is not enough. The record must explain why CT rather than X-ray or MRI
• Contrast rationale: for non-contrast studies, the record should show that no contrast was ordered, or explain why it was withheld
• Date of service and place of service
• Interpreting radiologist report: a signed, dated radiology report with findings and impression

Capturing these elements when the study is ordered removes most back-end rework. When the clinical note travels with the claim, the payer has less reason to ask for records before it pays.

ICD-10 codes that support medical necessity

The ICD-10-CM diagnosis code on the claim must support the medical necessity of 73700. Not every diagnosis code is accepted by every payer for lower extremity CT. Confirm coverage against the payer’s local coverage determination before submission.

A non-specific symptom code such as M79.671 needs strong supporting documentation behind it. Payers approve 73700 more readily when a structural diagnosis accompanies the claim. Work with your ordering providers to capture the most specific diagnosis available at the time of imaging.

Laterality and encounter character are where these codes are most often mistyped. When the documentation names a diagnosis outside the list above, the ICD-10-CM code index is the place to check both.

Bundling rules and NCCI edits

The National Correct Coding Initiative (NCCI) publishes quarterly updates to bundling edits. Those edits govern how 73700 interacts with other codes billed on the same date of service, and violating one triggers an automatic rejection.

Key bundling considerations for CPT Code 73700:

• 73700 with 73701 or 73702, same date and same extremity: the three codes are mutually exclusive for one anatomical region on one date. Bill only the one that reflects the acquisition protocol.
• CPT 76377 (3D rendering add-on): billable alongside 73700 when 3D images are independently generated and reviewed by the interpreting physician. The post-processing must appear in the radiology report. Coverage is payer-specific, so verify against current NCCI edits before appending.
• Modifier 59 use: when two separately payable imaging services fall on the same date, modifier 59 may be required to bypass automatic bundling edits. Appending 59 without a distinct service is a compliance risk.
• Bilateral billing: billing 73700 twice with LT and RT, without modifier 50 or payer-approved bilateral logic, may trigger duplicate claim edits.

NCCI edit tables change four times a year, so review your radiology codes each quarter. An edit that did not apply last quarter may be active today.

Common billing errors and how to avoid them

Radiology billing is denial-prone because contrast status, laterality, split billing, and add-on codes all have to align on one line. Each of the errors below is visible before submission if someone checks for it.

The most frequent errors on CPT Code 73700 claims:

• Wrong contrast code: billing 73700 when contrast was given, or 73701 and 73702 when it was not. Confirm with the technologist before coding.
• Missing medical necessity documentation: a diagnosis code alone does not establish necessity. The clinical record must explain why CT imaging was required at this stage of care.
• Incorrect modifier for split billing: billing global when a physician-only or facility-only component applies. This misallocates payment and invites an audit.
• Improper 76377 add-on billing: appending 76377 without documenting the physician’s use of the 3D images. Payers audit this combination frequently.
• Bilateral coding errors: omitting modifier 50, LT, or RT when both extremities are imaged, which triggers duplicate claim alerts.
• Outdated fee schedule rates in the billing system: prior-year expected amounts cause payment posting errors and inaccurate patient balances.

Pre-submission scrubbing catches most of these before the claim reaches the payer. The two checks that pay for themselves are contrast code against the acquisition record, and modifier against place of service.

Related CPT codes for lower extremity imaging

Coders working with lower extremity CT regularly meet related codes in the same region or modality family. The table below lists the most common companions and crosswalk references to CPT Code 73700.

When the clinical question is ligament or cartilage detail rather than bone, 73721 is usually billed instead. Confirm the modality with the ordering provider before you code, because a CT and an MRI of the same joint answer different questions.

How Pabau catches 73700 coding errors before submission

Radiology billing has more moving parts than most outpatient specialties. Split billing between components, quarterly NCCI updates, and payer-specific prior authorization rules all land on the same claim. So does modifier logic that changes with place of service.

Most practices find these problems on the remittance, weeks after the claim went out. Practice management software like Pabau moves the check forward instead. Pabau’s claims software for radiology connects to the Claim.MD clearinghouse and validates each claim before it is submitted.

The validation covers modifier logic, NCCI edit compliance, and diagnosis-to-procedure pairing. A 73700 line billed global when the hospital owns the scanner gets flagged inside the practice. You fix it once, rather than appeal it later.

For orthopedics, sports medicine, and podiatry, one record holds the appointment, the clinical note, the codes, and the remittance. That means fewer touches per claim, so your team spends less of the month chasing paperwork on high-volume imaging codes.

Catch radiology coding errors before submission

Pabau’s claims management connects to Claim.MD to validate CPT codes, flag modifier errors, and submit clean claims before they reach a payer. See how it works for orthopedic and radiology practices.

Book a demo

Conclusion

73700 is a precision code. Contrast alone decides which of three sibling codes applies, and the wrong pick generates a denial before a human reviewer ever sees the claim.

Get the contrast, the component, and the laterality right at the point of coding, and the rest of the claim follows. That discipline is worth more than a strong appeal process, because the cheapest denial is the one that never happens.

Book a demo to see how Pabau flags a bad modifier on a 73700 line before the claim ever leaves your practice.

Continue your research

Managing claim denials across your practice? Denial management in healthcare covers strategies for identifying, appealing, and preventing the most common claim rejections.

Working through a rejection on a radiology claim? Denial codes in medical billing explains what the most common codes mean and what each one asks you to fix.

Need to understand how clearinghouse pricing works? Claim.MD pricing guide breaks down how clearinghouse fees are structured and what to compare when evaluating options.

Brushing up on medical billing fundamentals? What is medical billing covers the end-to-end cycle from charge capture through payment reconciliation.

Frequently asked questions