NPIMap

Individual provider Active NPI

William Sanderson Twaddell, M.D.

  • Anatomic Pathology & Clinical Pathology Physician
  • Baltimore, MD
National Provider Identifier
1538296124
Registry record updated May 7, 2026
On this page

Key facts

NPPES NPI Registry
Primary specialty
Anatomic Pathology & Clinical Pathology PhysicianTaxonomy code 207ZP0102X
License
D68076 Issued in MD
Practice address
22 S Greene St
Nbw73
Baltimore, MD 21201-1544
Phone
(410) 328-5555
Fax
(410) 328-0929
NPI assigned
Feb 28, 2007
Last updated
May 7, 2026By the provider in NPPES
Sex
Male
Sole proprietor
No

NPPES NPI Registry

Updated by the provider on May 7, 2026

Registry information is reported by the provider to CMS and is not verified. About this source

Specialties & licenses 2

Specialty (taxonomy)CodeLicenseStatePrimary
Anatomic Pathology Physician 207ZP0101X 242497-1 NY
Anatomic Pathology & Clinical Pathology Physician 207ZP0102X D68076 MD Primary

Addresses

Primary practice location

22 S Greene St
Nbw73
Baltimore, MD 21201-1544

Mailing address

22 S Greene St
Nbw73
Baltimore, MD 21201-1544
Phone (410) 328-5555

Other names 1

  • William S Twaddell Other name

Medicare participation

Medicare enrollment files
Medicare fee-for-service enrollment
Enrolled in MD
Eligible to order & refer
  • Part B services
  • Medical equipment
  • Home health
  • Power mobility devices
  • Hospice
Green means eligible to order or refer.

Enrollment records 1

Enrollment IDStateProvider typePAC IDDetails
I20080917000265 MD Practitioner - Pathology 9133214240 Reassigns benefits to 3 organizations

Care Compare profile

Medicare Care Compare
Specialty
Pathology
Education
Columbia University College of Physicians and Surgeons, 2004
Medicare assignment
Accepts the Medicare-approved amount as payment in full
Group practices
Chester River Hospital CenterGroup PAC ID 0749220671, 28 clinicians
Digestive Disease Solutions LLCGroup PAC ID 7517191505, 3 clinicians

Practice addresses (Care Compare)

100 Brown St
Chestertown, MD 21620-1435
Phone (410) 778-3300

22 S Green St
Baltimore, MD 21201-1544
Phone (410) 328-5555

804 Toll House Ave
Frederick, MD 21701-4519
Phone (301) 695-7000

Hospital & facility affiliations

National Provider Directory

National Provider Directory
Medicare enrollment (NPD)
Enrolled
Credentials
Doctor of Medicine

State licenses

LicenseStateTypeSpecialty
242497-1NYMDAnatomic Pathology Physician

Practice roles

OrganizationSpecialtyStatusNew patients
Chester River Health Center CurrentSince Oct 1, 2024 Accepting new patients
Univ of MD Pathology Associates P a Current Accepting new patients
Digestive Disease Solutions, LLC CurrentSince Aug 1, 2024 Accepting new patients
Chester River Hospital Center Current Accepting new patients
Univ of MD Pathology Associates P a CurrentSince Aug 18, 2008 Accepting new patients
Kent Queen Anne Pathology CurrentSince Oct 1, 2024 Accepting new patients
Metro Maryland Anesthesia LLC PastSince Mar 9, 2020 Accepting new patients
University of Maryland Dermatologists PA PastSince Nov 8, 2025 Accepting new patients

Locations

22 S Greene St
Baltimore, MD 21201
Phone (410) 328-5793

22 S Greene St
#73
Baltimore, MD 21201
Phone (410) 328-5514

419 W Redwood St
Ste 200
Baltimore, MD 21201
Phone (410) 328-3408

100 Brown St
Chestertown, MD 21620
Phone (410) 778-3300

219 S Washington St
Easton, MD 21601

804 Toll House Ave
Frederick, MD 21701
Phone (301) 695-7000

Organizations & group practices 8

Organizations this provider is connected to: Medicare benefit reassignments (the organization bills Medicare for this provider’s services), Care Compare group memberships, National Provider Directory roles and organizations whose NPPES authorized official is this provider.

Hospital & facility affiliations 8

Hospitals and other facilities this clinician is affiliated with according to Medicare Care Compare.

NPI Registry JSON

The complete NPPES record for this NPI in the NPI Registry API format.

{
    "created_epoch": "1172620800000",
    "enumeration_type": "NPI-1",
    "last_updated_epoch": "1778112000000",
    "number": "1538296124",
    "addresses": [
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "MAILING",
            "address_type": "DOM",
            "address_1": "22 S GREENE ST",
            "address_2": "NBW73",
            "city": "BALTIMORE",
            "state": "MD",
            "postal_code": "212011544",
            "telephone_number": "410-328-5555",
            "fax_number": "410-328-0929"
        },
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "LOCATION",
            "address_type": "DOM",
            "address_1": "22 S GREENE ST",
            "address_2": "NBW73",
            "city": "BALTIMORE",
            "state": "MD",
            "postal_code": "212011544",
            "telephone_number": "410-328-5555",
            "fax_number": "410-328-0929"
        }
    ],
    "practiceLocations": [],
    "basic": {
        "last_name": "TWADDELL",
        "first_name": "WILLIAM",
        "middle_name": "SANDERSON",
        "credential": "M.D.",
        "sole_proprietor": "NO",
        "sex": "M",
        "enumeration_date": "2007-02-28",
        "last_updated": "2026-05-07",
        "certification_date": "2026-05-07",
        "status": "A"
    },
    "taxonomies": [
        {
            "code": "207ZP0101X",
            "taxonomy_group": "",
            "desc": "Pathology, Anatomic Pathology",
            "state": "NY",
            "license": "242497-1",
            "primary": false
        },
        {
            "code": "207ZP0102X",
            "taxonomy_group": "",
            "desc": "Pathology, Anatomic Pathology & Clinical Pathology",
            "state": "MD",
            "license": "D68076",
            "primary": true
        }
    ],
    "identifiers": [],
    "endpoints": [],
    "other_names": [
        {
            "first_name": "WILLIAM",
            "last_name": "TWADDELL",
            "middle_name": "S",
            "credential": "MD",
            "code": "5",
            "type": "Other Name"
        }
    ]
}

Other providers in Baltimore, MD

Sources for this page

Verify at the official NPI Registry.