Zachary Callahan, MD
Surgery · Nashville, TNNPI 1679969067
Payments from drug & device makers
What this record shows
This record is dominated by grants: $50,000 of the $65,486 with a category attached, or 76.4%. Boston Scientific accounts for 76.4% of it on its own, with 13 other manufacturers making up the rest. Reporting peaked in 2022 at $25,394 and has fallen 78.1% since, to $5,551 in 2025. Among surgery clinicians in TN with any reported payments, this total sits in the top 5% — high for the specialty, which is a reason to read the composition above rather than the number alone.
Across 87 payments — averaging $752.72 each. Meals, travel, consulting and speaking fees, gifts and royalties reported by drug and device makers.
- Boston Scientific$50K
- Intuitive Surgical$13K
- Apollo Endosurgery US Inc$1K
- W. L. Gore & Associates, Inc.$855
- Medtronic$376
- Johnson & Johnson$143
- plus $341 from 8 others
What the payments were for
- Grants$50,00076%
- Travel & lodging$4,9037%
- Food & beverage$3,3695%
- Education$7,21511%
General payments by program year
Who reported the general payments
Companies are grouped under their corporate parent — a single manufacturer often files under several CMS reporting entities. Research and ownership payments are counted separately and are not in this table.
| Company | Payments | Total |
|---|---|---|
| Boston Scientific | 3 | $50,045 |
| Intuitive Surgical | 46 | $12,552 |
| Apollo Endosurgery US Inc | 9 | $1,174 |
| W. L. Gore & Associates, Inc. | 10 | $855 |
| Medtronic | 8 | $376 |
| Johnson & Johnson | 1 | $143 |
| Enterra Medical, Inc. | 2 | $122 |
| Stryker | 1 | $68 |
| Baxter Healthcare | 1 | $54 |
| Conmed Corporation | 2 | $31 |
| Pacira Pharmaceuticals Incorporated | 1 | $19 |
| Innovation Technologies Inc | 1 | $18 |
| Olympus America Inc. | 1 | $16 |
| Acera Surgical, Inc. | 1 | $13 |
What the payments were tied to
Products named in the reported payments. Only payments of $100 or more are attributed here — the typical reported payment nationally is a meal worth about $16, and listing those product-by-product would be noise.
- GENERAL - BILIARY DEVICES$50,000
- DAVINCI XI$7,000
- Da Vinci Surgical System$4,638
- OverStitch Endoscopic Suturing System$906
- GORE BIO-A Tissue Reinforcement$169
- EXCLUDER Conformable AAA Endoprosthesis with Active Control$157
- ORBERA Intragastric Balloon System$152
- Echelon Circular$143
- ECHELON ENDOPATH$143
- Harmonic$143
- EndoFlip$128
- GORE ENFORM Preperitoneal Biomaterial$120
- GORE SYNECOR Biomaterial$117
How this compares
$65,486 in reported general payments places this provider in the 95th percentile of 516 surgery providers in Tennessee.
Medicare billing
What this is not: this is the amount Original Medicare Part B allowed for services this provider billed in 2024. It is not their income. It excludes Medicare Advantage — now more than half of all Medicare enrollment — along with Medicaid and all commercial insurance, and it is gross practice revenue before staff, rent, supplies and malpractice premiums. CMS also suppresses any figure covering ten or fewer patients, so low-volume providers appear smaller than they are.
Most prescribed under Part D
| Drug | Claims | Cost to plans & patients |
|---|---|---|
| Omeprazole | 30 | $485 |
| Oxycodone Hcl | 12 | $20 |
Paid to pharmacies, not to this prescriber.
Other surgery in Nashville
- Evelio RodriguezNashville$362K
- Mathew NinanNashville$298K
- Joseph BroucekNashville$262K
- Ashok BabuNashville$126K
- Meredith DukeNashville$77K
- Joseph DelozierNashville$44K
- Laura LawsonNashville$36K
- Richard PierceNashville$23K
- David DyerNashville$23K
- Roshni VenugopalNashville$21K
Where these figures come from
- Payments: CMS Open Payments, program years 2019–2025 (publication P06302026_06032026).
- Billing: Medicare Physician & Other Practitioners, data year 2024. Original Medicare Part B only.
- Identity: NPPES NPI Registry, July 2026.