CPT code 61321: Abscess drainage, infratentorial approach2026 Medicare rate & RVUs in Massachusetts
Reports open surgical drainage of an intracranial abscess below the tentorium, such as a cerebellar abscess, through a craniotomy or craniectomy.
CMS doesn’t publish an office rate for 61321 in Massachusetts.
Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.
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What 61321 covers
A neurosurgeon uses a craniotomy or craniectomy to reach and drain an abscess in the infratentorial compartment, which includes the posterior fossa and cerebellum. The operation is typically performed in a hospital operating room for a patient with an intracranial infection requiring open surgical drainage. This code distinguishes infratentorial abscess drainage from drainage of a supratentorial abscess.
Select the code based on the abscess location and the procedure performed, not merely on the incision site or the presence of infection. The operative report should identify the infratentorial target and document surgical drainage. The service has a 90-day global period, including the day-before preoperative visit and 90 days of related postoperative care. When multiple procedures occur in the same session, the highest-valued procedure is paid in full and others at 50%. Modifier 50 is inappropriate. Assistant-at-surgery payment may be available; co-surgeon payment requires supporting documentation, and team surgery is 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.
Where 61321 pays more and less in Massachusetts
| Payment locality | Office | Facility |
|---|---|---|
| Metropolitan Boston, MA | Unavailable | $2,190.74 |
| Rest of Massachusetts | Unavailable | $2,034.49 |
How the 61321 rate is calculated
Each of 61321’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 · 61321
RVUs × geographic indexes × conversion factor
Work29.77
29.77 RVUs× 1.000 GPCI
Practice expense19.60
19.60 RVUs× 1.000 GPCI
Malpractice12.58
12.58 RVUs× 1.000 GPCI
Adjusted RVUs
61.9500
Conversion factor
$33.4009
Medicare rate
$2,069.19
Every GPCI starts at 1.000, the national rate. Enter a ZIP or drag a slider.
Payment rules and modifiers for 61321
61321 has a 90-day global period: related visits in that window are included in the surgery payment.
CMS payment indicators · 61321
Abscess drainage, infratentorial approach
| Rule | CMS value | What it means |
|---|---|---|
| Global period | 090 | Major surgery: the day before, the day of, and 90 days after are included. |
| Multiple procedures | 2 | Standard reduction: highest-valued procedure at 100%, others at 50%. |
| Bilateral (modifier 50) | 0 | The 150% bilateral adjustment doesn’t apply. |
| Assistant at surgery (80/81/82/AS) | 2 | Paid. |
| Co-surgeons (62) | 1 | Permitted with supporting documentation. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 0 | Physician service: no professional/technical split. |
| Split (54/55/56) | 0.11/0.76/0.13 | Share of the payment for pre-op, the procedure itself, and post-op care. |
Global surgery period · 61321
Abscess drainage, infratentorial approach
90-day global period ends
Dec 30, 2026
Covers Sep 30, 2026 through Dec 30, 2026 (92 days, including the day before surgery).
Visit on Oct 31, 2026
Day 30 of the 90-day post-op period: related follow-up care is included in the surgical payment.
Pre-op dayGlobal period
What modifiers do to the payment
Modifier 51 · payment effect
With and without the modifier
61321 without 51 · national facility
$2,069.19
Abscess drainage, infratentorial approach
61321-51 · Second procedure: 50%
$1,034.60
When this isn’t the highest-valued procedure in the session, Medicare pays 50% of its fee schedule amount (the highest is paid at 100%).
61321 compared with similar codes
Compare codes · National
5 codes, side by side
How to choose
- 61320Abscess drainageSupratentorial, open approach
- Both codes describe open drainage of an intracranial abscess; choose 61321 for an infratentorial target and 61320 for a supratentorial target.
- 61107Ventricular catheterTwist-drill access
- This code describes twist-drill drainage of an intracranial collection, including an abscess; 61321 describes open drainage through a craniotomy or craniectomy.
- 61750Brain biopsyWithout CT/MR guidance
- This code describes stereotactic biopsy, aspiration, or excision of an intracranial lesion. Use 61321 when the abscess is drained through an open infratentorial approach.
- 61314Hematoma evacuationInfratentorial, extradural or subdural
- 61314 concerns evacuation of an infratentorial extradural or subdural hematoma, not drainage of an abscess.
61321 billing questions
How does this code differ from 61320?
Use 61321 for an abscess below the tentorium, such as in the posterior fossa. Code 61320 is the corresponding service for a supratentorial abscess.
What documentation supports 61321?
The operative report should establish the infratentorial location and describe the open surgical drainage. A diagnosis of intracranial abscess alone does not establish the site distinction.
Can 61321 be reported with modifier 50?
No. CMS identifies bilateral adjustment as inappropriate for this code.
How are assistant and co-surgeon services handled?
Assistant-at-surgery payment may be made. Co-surgeons are paid only when supporting documentation is provided; team surgery is not permitted.
What is included in the global period?
The 90-day global period includes the day-before preoperative visit and 90 days of related postoperative care.
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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