The vast majority of 93971 denials have nothing to do with the US. The tech read it correctly. The doctor was correct about the pictures. Then the claim went out with a note that said “venous duplex, leg” and a diagnosis that pointed to the wrong side, and the payer said no.
That's a paperwork problem, and it's fixable. Our team at A2Z Billings has 150+ years combined billing and coding experience. Vascular studies are one of the areas where we see the same few mistakes costing practices money month after month. This guide will explain what the code covers, what your record should show, and why claims are denied so you can avoid losing revenue. No matter if you bill from an office vascular lab, an imaging centre or a hospital outpatient department, everything below regarding documentation for CPT 93971 is true.
What CPT 93971 covers
Description. Duplex scan of extremity veins with responses to compression and other manoeuvres; unilateral or limited study. It works with both arms and legs. One word in that description causes confusion: limited.
A limited study is not always a one-leg study. If the tech scans both legs but only part of the venous system on each leg, the correct code is still 93971, not 93970. The bilateral study is partial, not fully absorbing unilateral or limited codes. Code 93970 is for a full bilateral study, and no less.
'Duplex' is also a technical word. All greyscale imaging, colour flow, and spectral Doppler waveforms must be performed and documented. The use of colour Doppler just to find a vessel does not make an ultrasound a duplex study. If you remove the spectral piece from the record, the code falls apart.
Complete versus limited: where the money leaks
The billing guidance from HAP Radiology lays out the logic. A study that has less than the correct number of vessels is paid for as limited. A complete study of the upper extremities requires the record of the subclavian, jugular, axillary, brachial, basilic and cephalic veins of both arms. Forearm veins are optional. Calf veins are optional for the legs, but the required segments must be present on both sides.
So this is what happens. One practice bill, 93970, for a bilateral study; the report skips one segment, and a payer that downcodes or denies. It’s free to repair. Describe the type of study in plain language and link to the code. Something like 'right lower extremity venous duplex, complete unilateral study, deep and superficial systems. 'No argument is possible. Plenty leaves "leg veins, normal."
Arm studies get audited too
Most of the discussion about this code deals with legs. However, 93971 also covers upper extremity veins, and those claims fall for the same reasons. The report says 'upper extremity venous duplex' after a central line or PICC; no one puts down the veins, and the tech scans the right arm for swelling. Payers want the side and vessels: subclavian, axillary, brachial, basilic, cephalic and jugular if imaged. The code is also valid for limited hand and digit studies. So the report should say exactly where the probe went. The whole claim is tied together with one sentence on the line indication, such as swelling in the arm after the placement of a catheter.
What your record needs to show
Payers want to know why the study was ordered, what was scanned, and what was found. A record that has all three is rarely refused on documentation grounds. Make the note around this list:
- An order that identifies the symptom or risk factor that is causing it, such as calf pain, leg swelling, recent surgery or suspected clot.
- The side and extremity should be written out as right, left, or both.
- Each vein is named one by one as the study is performed, and a statement is made about whether the study is complete or limited.
- Technique: greyscale, colour flow, spectral doppler and compression with augmentation manoeuvres.
- Compressibility, flow pattern, and thrombus or reflux results are recorded for each segment.
- Images are stored, and a signed interpretation is provided by the physician.
Miss one, and a reviewer has a reason to say no. A report that reads "lower extremity veins" with no vessel list is the classic example, and auditors flag that kind of vague scope statement on sight.
Medical necessity and diagnosis pairing
Claim read. Documentation. Receives. Medical necessity gets it covered.
Medicare contractors’ rules for venous duplex coverage. LCD L35751 includes peripheral venous studies 93965, 93970 and 93971 and includes the ICD-10 codes that support them. Examples from this list are I80.01 and I80.02 for superficial phlebitis of the right and left legs and I82.491 to I82.493 for acute thrombosis of other specified deep veins of the right leg, left leg or both. NGS has its own LCD, L33627, which states that results are expected to affect patient management and that multiple same-day studies are uncommon.
Do not screen asymptomatic patients for varicose veins unless there is documented indication. If you are not going to change what you do for the patient with the study, you should expect pushback.
Match the diagnosis to the extremity. Right leg diagnosis for a scan of the right leg For example, R22.41 for localised swelling of the right lower limb and I82.401 for acute thrombosis of the deep veins of the right leg. Laterality mismatches are some of the easiest errors to avoid, and we constantly see them. Coverage lists are updated on a yearly basis, so check the current LCD article before you code, instead of using last year’s cheat sheet.
Common denials and how to fix them
Documentation did not meet the LCD.
AAPC’s Part B Insider covered NGS reviews of vascular studies, and the headline number was ugly: about 80 percent of claims were coded incorrectly. The two most common reasons for denial were lack of documentation meeting LCD standards and records with no clinical indication for the study. The fix is the above list. Take the symptom, then order it into the report.
Vague or missing scope
A report that says “bilateral venous duplex” without a list of vessels gives the payer nothing to verify. The payer cannot distinguish between full and partial studies, so it may downcode or deny the claim. Name all the veins.
93970 and 93971 on the same claim
Assigned one venous duplex code per encounter to one extremity region. If you bill the same arm or same leg, the second line gets rejected. If a patient has an arm scan and a leg scan on the same day, those are separate regions, and each needs its own documented reason.
Venous and arterial duplex on the same day
Some commercial edit rules, EmblemHealth's among them, will not pay 93970 or 93971 alongside the arterial duplex codes 93922 through 93931 unless separate medical necessity is on file. Medicare contractors treat same-day studies the same way. Give each study its symptom and its own diagnosis, or expect a denial of one of them.
Duplicate claims and ignored record requests
The NGS findings also noted duplicate claim denials and a failure to respond to a request for medical documentation. Both are cheap to repair. Remember the request deadline, send the order, the complete report and clinical notes all in one packet, and never resubmit a claim while the first is still pending.
Repeat scans without a new reason.
A confirmed clot patient returns in a week for a follow-up scan. The second claim is identical to the first, so the payer’s frequency edit is triggered. Follow-up studies are often legitimate (check for clot extension, decide whether to continue anticoagulation) but only if the note says so. In order, enter what changed, what symptom remains, and what decision depends on the result. Without it, a repeat study is read as a duplicate study.
Missing prior authorization
Many commercial plans require prior authorisation for non-urgent venous duplex. Check the payer portal prior to the scan, not after. A no-auth denial of an already-done study is particularly difficult to overturn.
Modifiers and the professional split
To be honest, the professional split is where small offices get stuck. The physician will bill the professional component with modifier 26, and the hospital or imaging centre will bill the technical component with TC. “You add a global component modifier from your office, on your own equipment.” Many payers want laterality modifiers, so add RT or LT to one-sided studies. Use the X modifier or Modifier 59 only if an edit links 93971 with another study and the record indicates a separate reason for each. 1. Review each payer policy.
A two-minute check before every claim
Before a 93971 claim leaves your office, check four things. The order identifies a symptom or risk factor. The report lists the side and the name of each vein. Diagnosis is the same as the limb and current LCD list. No other duplex code can be claimed without having a reason. If you fail, keep the claim and fix it. A clean claim is paid on first submission. The denied one eats up staff time in rework, appeals and waiting. Some never come back once the appeal window closes.
Frequently asked questions
What does CPT 93971 mean?
It is the code for a duplex scan of veins in an extremity, performed with compression and other manoeuvres, and may be unilateral or limited. It covers leg and arm veins.
What is the difference between 93970 and 93971?
Code 93970 is a total bilateral study. 93971 is for unilateral or any limited study, including a bilateral scan that misses required vessels.
Can I bill 93971 when both legs are scanned?
Yes, if the bilateral study is restricted. 93970. The correct code is 93970 if all vessels needed are recorded on both sides.
Can 93970 and 93971 be billed together?
Not for the same extremity region in the same encounter. Pick the one that matches what was done.
Does Medicare cover duplex ultrasonography for screening?
No, sir. Medicare contractors require evidence of a sign, symptom or risk factor. Screening without asymptomatic varicose veins generally does not meet the test of medical necessity.
What ICD-10 codes support 93971?
Common ICD-10-CM codes for deep vein thrombosis are I82.401, I82.491-I82.493; for superficial phlebitis are I80.01 and I80.02; and for right lower limb swelling is R22.41. Check out the latest LCD billing article.
How do I appeal a 93971 denial?
Submit the physician’s order, signed report, clinical notes showing the symptom and a brief letter stating which coverage criteria the record satisfies. First, check the payer’s appeal deadline, which is often short.
Stop losing paid claims on a covered study
A2Z Billings matches speciality coders with front-end checks to ensure documentation gaps are identified before the claim is sent out. We trace every denial back to its source so that the same mistake does not recur next month. Send us your last batch of denied venous duplex claims, and we will show you where each one broke. Get in touch with A2Z Billings today.