Procedure Occurrence

Epic equivalent: Procedure orders / Surgical case records / Radiology orders / CPT-coded billing entries

The procedure_occurrence table captures medical procedures performed on a patient — surgeries, imaging studies, vaccinations, biopsies, and other interventions. In Epic, this data comes from procedure orders, surgical case records, radiology modules, and CPT/HCPCS-coded billing. In OMOP, procedures are standardized to SNOMED (mapped from CPT, HCPCS, ICD-10-PCS).

Each row is a single procedure event.

Epic-to-OMOP Field Mapping

Field reference (click to expand)

OMOP Field	Epic Equivalent	What It Captures
procedure_occurrence_id	Procedure record ID	Unique identifier
person_id	Patient ID / MRN	Links to the patient
procedure_concept_id	SNOMED standard concept	Standardized procedure (mapped from CPT/HCPCS). Use for analysis
procedure_date	Date of procedure	When performed; procedure_datetime has time precision
procedure_type_concept_id	Data provenance	Whether from EHR, billing, registry, etc.
modifier_concept_id	CPT modifiers	Laterality, approach, or other refinements (often missing)
quantity	Count performed	How many times in this instance
provider_id	Performing provider	Who performed the procedure
visit_occurrence_id	Linked encounter	Visit context
procedure_source_value	CPT / HCPCS / ICD-10-PCS code	Original code from the source system

What to Watch For

Common pitfalls

Domain overlap

Imaging (e.g., MRI) may appear in procedure_occurrence, measurement, or both depending on capture method. Verify context before analysis.

One row per event, not per visit

A patient with 3 procedures in one visit has 3 rows. Don't assume one procedure per encounter.

Modifiers are often missing

modifier_concept_id is sparsely populated in most EHR-derived OMOP instances.

Research Patterns

Question	Tables Involved
Colonoscopy frequency in the past 5 years	procedure_concept_id (colonoscopy) + procedure_date
Mastectomy vs. lumpectomy rates in breast cancer	procedure_occurrence + condition_occurrence (breast cancer)
Cardiac catheterization followed by CABG	procedure_occurrence sequenced by procedure_date
Joint replacement volume by surgical center	procedure_occurrence + care_site_id
Time from prostate biopsy to definitive surgery	procedure_occurrence (biopsy + prostatectomy) + date diff