Billing code 50431: Antegrade contrast studyMedicare rate & RVUs in Guam
Reports a contrast study of the renal collecting system and ureter performed through newly established percutaneous access to assess drainage, patency, or obstruction.
Medicare pays $343.01 for 50431 in the office in Guam (Hawaii, Guam). Which amount applies depends on the service address.
Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.
On this page 9 sections
What 50431 covers
An antegrade nephrostogram or ureterogram traces contrast from the kidney’s collecting system down the ureter. Code 50431 identifies a diagnostic study reached by creating new percutaneous access, rather than injecting contrast through an already-present nephrostomy catheter. An interventional radiologist or urologist typically uses ultrasound or fluoroscopy to guide access, injects contrast, and interprets the images in an interventional radiology suite or hospital procedure room. The study can help clarify suspected obstruction, a leak, or impaired drainage.
Report 50431 when the new access is used for the contrast examination and a catheter placement service does not account for the work. Nephrostomy or nephroureteral catheter placement codes include the diagnostic contrast study when performed, so do not separately report 50431 for that included imaging. Document the indication, newly obtained access, contrast examination, findings, and laterality. CMS assigns a 0-day global period, including same-day preoperative and postoperative care. For bilateral service, modifier 50 is paid at 150%. In a session with multiple procedures, the highest-valued procedure is paid in full and others at 50%. Assistant-at-surgery payment is barred; co-surgeon and team-surgery billing are not permitted.
This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.
50431 in Hawaii, Guam
| Payment locality | Office | Facility |
|---|---|---|
| Hawaii, Guam | $343.01 | $60.09 |
How the 50431 rate is calculated
Each of 50431’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.
How the rate is built · 50431
RVUs × geographic indexes × conversion factor
Swap in your local Medicare rate.
Work 1.07Practice expense 8.03Malpractice 0.12
All indexes start at 1.000 (the national rate). Enter a ZIP or drag a slider.
Payment rules and modifiers for 50431
The CMS indicators that decide how 50431 is paid alongside other services.
CMS payment indicators · 50431
Antegrade contrast study
| Rule | CMS value | What it means |
|---|---|---|
| Global period | 000 | Same-day global: pre- and post-op care on the day of the procedure is included. |
| Multiple procedures | 2 | Standard reduction: highest-valued procedure at 100%, others at 50%. |
| Bilateral (modifier 50) | 1 | Bilateral with modifier 50 pays 150% of the fee schedule amount. |
| Assistant at surgery (80/81/82/AS) | 1 | Not paid (statutory restriction). |
| Co-surgeons (62) | 0 | Not permitted. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 0 | Physician service: no professional/technical split. |
What modifiers do to the payment
Modifier 50 · payment effect
With and without the modifier
50431 without 50 · national office
$307.96
Antegrade contrast study
50431-50 · Bilateral: 150%
$461.94
Both sides on one line with modifier 50 are paid at 150% of the fee schedule amount (subject to multiple-procedure rules with other procedures).
50431 compared with similar codes
Compare codes
50431 vs 50430 vs 50432 vs 50433: national Medicare rates
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How to choose
- 50430Antegrade nephrostogram
- Choose 50431 when the contrast study requires new percutaneous access. Choose 50430 when contrast is injected through existing access.
- 50432Nephrostomy placement
- 50432 covers percutaneous nephrostomy catheter placement, including the diagnostic contrast study when performed. 50431 is for the contrast study through new access when catheter placement is not the service reported.
- 50433Catheter placement
- 50433 covers nephroureteral catheter placement, including the diagnostic contrast study when performed. 50431 describes the new-access contrast study without that catheter placement service.
50431 billing questions
How does 50431 differ from 50430?
50431 is for a contrast study reached through newly created percutaneous access. Use 50430 when the study uses existing access, such as an established nephrostomy catheter.
Can 50431 be reported with nephrostomy catheter placement?
The nephrostomy placement code includes the diagnostic nephrostogram or ureterogram when performed. Do not separately report 50431 for that included study.
Is imaging guidance or interpretation separately reported?
The code includes imaging guidance and the associated radiological interpretation for the contrast study.
How is bilateral service reported?
Report modifier 50 for bilateral service. CMS pays the bilateral procedure at 150%.
What documentation supports 50431?
Document why the study was needed, that access was newly obtained, the contrast examination and its findings, and the side or sides examined.
Where these rates come from
FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.
CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027
Show the CMS file lines behind this rate
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