Quick answers
- Does Aaron B. Greenspan accept Medicare assignment?
- Yes. Medicare's clinician data says Aaron B. Greenspan accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of October 2, 2026. Ask the office to confirm before your visit.
- How many Medicare patients does Aaron B. Greenspan see?
- In 2024, CMS data shows 211 Original Medicare patients and 350 services for Aaron B. Greenspan. This counts Original Medicare only and measures volume, not quality.
- What is Aaron B. Greenspan's NPI number?
- 1558382911. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Medicare activity in 2024
Official CMS public-use data for Aaron B. Greenspan, data year 2024 (released May 21, 2026). It covers Original Medicare (fee-for-service) patients only, not Medicare Advantage or other insurance. It shows volume, not quality or outcomes. CMS hides any count of 10 or fewer patients.
| Original Medicare patients | 211 |
|---|---|
| Services billed to Medicare | 350 |
| Different services or procedures | 41 |
| Participating Medicare provider | Yes |
| Average age of these patients | 73 |
Most frequent services
- Diagnostic exam of large bowel using a flexible endoscope (45378)41 services
- Established patient office or other outpatient visit with low level od decision making, if using time, 20 minutes or more (99213)41 services
- Biopsy of large bowel using a flexible endoscope (45380)37 services
- Removal of polyps or growths of large bowel using an endoscope with mechanical snare (45385)30 services
- Subsequent hospital care with straightforward or low level of medical decision making, per day, if using time, at least 25 minutes (99231)26 services
Chronic conditions among these patients
Share of this clinician’s Original Medicare patients with each condition, as published by CMS (it describes the patients, not the care given).
- High blood pressure75%
- High cholesterol75%
- Arthritis53%
- Ischemic heart disease38%
- Chronic kidney disease35%
- Diabetes34%
Hospitals where Aaron B. Greenspan works
Medicare's Facility Affiliation Data lists Aaron B. Greenspan at these hospitals (updated October 2, 2026). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians. Star rating and emergency services: Hospital General Information (CMS), data updated October 26, 2026.
- Barnes Jewish HospitalSaint Louis, MO · Acute Care Hospital · Medicare rating: 4 of 5 stars · Emergency services: listed by Medicare · CCN 260032
- Carlinville Area HospitalCarlinville, IL · Critical Access Hospital · Medicare rating: 2 of 5 stars · Emergency services: listed by Medicare · CCN 141347
- Missouri Baptist Medical CenterSaint Louis, MO · Acute Care Hospital · Medicare rating: 5 of 5 stars · Emergency services: listed by Medicare · CCN 260108
- Pana Community HospitalPana, IL · Critical Access Hospital · Medicare rating: 4 of 5 stars · Emergency services: listed by Medicare · CCN 141341
Practice locations
Addresses where Aaron B. Greenspan is enrolled with Medicare (CMS data updated October 2, 2026).
- 1 Barnes Jew Hosp PlzSaint Louis, MO 63110 (314) 747‑3000
- 101 E 9th StPana, IL 62557 (217) 562‑6246
- 20733 N Broad StCarlinville, IL 62626 (217) 854‑3141
- 217 S Locust StPana, IL 62557 (217) 562‑2143
Group practices
Medicare enrollment lists Aaron B. Greenspan as a member of these groups (CMS data updated October 2, 2026).
- Washington University3,029 clinicians in the group
- Pana Community Hospital Association56 clinicians in the group
- Carlinville Area Hospital Association24 clinicians in the group
Specialties
- Gastroenterologyprimary
- Internal Medicinealso
Other gastroenterologists in Saint Louis
Clinicians with the same Medicare primary specialty in Saint Louis, MO — not a recommendation.
Other clinicians in Washington University
Medicare enrollment lists these clinicians in the same group practice — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | University Of Pittsburgh School Of Medicine |
| Graduation year | 1991 (35 years since medical school) |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1558382911 |
| Corrections | Report an error or suggest an update → |
Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.
Sources
- Facility Affiliation Data — Centers for Medicare & Medicaid Services (CMS), data updated October 2, 2026, retrieved October 29, 2026
- Hospital General Information — CMS, data updated October 26, 2026, retrieved November 13, 2026
- National Downloadable File (Doctors and Clinicians) — CMS, data updated October 2, 2026, retrieved October 29, 2026
- Medicare Physician & Other Practitioners - by Provider — CMS, data year 2024, released May 21, 2026; Medicare Physician & Other Practitioners - by Provider and Service
- NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
- Medicare Care Compare — official Medicare tool to look up clinicians