CPT code 45378 reports a diagnostic flexible colonoscopy when no separately reportable biopsy, polypectomy, ablation, or other therapeutic intervention is performed.
CPT 45378 includes specimen collection by brushing or washing. If tissue is biopsied or a lesion is treated, the applicable biopsy or therapeutic code replaces 45378.
An incomplete professional colonoscopy may still be reported with modifier 53 when CMS requirements are met.
This guide explains CPT 45378 billing, coding, reimbursement, Medicare rules, documentation, modifiers, and claim submission best practices.
Official Description Of CPT Code 45378
The official description of CPT code 45378 is: “Colonoscopy, flexible; diagnostic, including collection of specimen(s) by brushing or washing, when performed (separate procedure).”
Three elements matter:
- Diagnostic: The code reports the diagnostic examination. A separately reportable biopsy or therapeutic procedure requires the applicable colonoscopy code.
- Brushing or washing: These collections are included in 45378 and are not reported as tissue biopsies.
- Separate procedure: Do not report 45378 when the diagnostic examination is included in a more comprehensive endoscopic service.
CMS NCCI policy states that surgical endoscopy includes diagnostic endoscopy. Therefore, do not report 45378 with a therapeutic colonoscopy code merely to describe the diagnostic portion of the same examination.
More than one therapeutic colonoscopy code may be reported when distinct procedures are performed on separate lesions and NCCI and modifier requirements are met.
What Does CPT 45378 Describe?
A complete colonoscopy generally reaches the cecum or a colon-small-intestine anastomosis. Examination of the terminal ileum is not required.
The report should document the indication, maximum insertion depth, landmarks, findings, interventions, completeness, and reason for stopping if incomplete.
An examination limited to the rectum, sigmoid colon, or another limited section may support flexible sigmoidoscopy coding. Passing the splenic flexure alone does not establish a complete colonoscopy.
If an unforeseen circumstance prevents the scope from reaching the cecum or anastomosis, modifier 53 may be reported on the professional claim. Outpatient hospital and ASC facility claims use separate discontinued-procedure rules and may require modifier 73 or 74.
CPT 45378 Compared With Other Colonoscopy Codes
CPT 45378 applies to a diagnostic colonoscopy without biopsy or treatment. The comparison below shows when other colonoscopy and Medicare screening codes apply instead.
| Code | Procedure |
| 45378 | Diagnostic flexible colonoscopy, including brushing or washing |
| 45380 | Colonoscopy with biopsy |
| 45384 | Removal by hot biopsy forceps or bipolar cautery |
| 45385 | Removal by snare |
| 45388 | Ablation of a lesion |
| G0105 | Medicare screening colonoscopy for a qualifying high-risk patient |
| G0121 | Medicare screening colonoscopy for a qualifying patient who does not meet high-risk criteria |
Use 45378 when no separately reportable biopsy or therapeutic procedure is performed. Do not report it with a therapeutic code for the same diagnostic examination.
Screening, Diagnostic, and Surveillance Colonoscopy
Screening colonoscopy is performed as a colorectal cancer screening service for an eligible patient without symptoms or a condition requiring evaluation.
Diagnostic colonoscopy is performed due to symptoms, abnormal findings, abnormal test results, or evaluation/management of a known condition.
A screening colonoscopy may identify a polyp or other abnormality. When biopsy, polypectomy, or another therapeutic intervention is performed, Medicare converted-screening rules apply, including reporting the therapeutic procedure(s) with the appropriate screening conversion modifier.
Surveillance colonoscopy is performed because of a prior history of colorectal polyps, colorectal cancer, or another qualifying condition. Depending on the patient’s risk category and Medicare criteria, some asymptomatic high-risk patients may qualify for screening colonoscopy reporting with G0105.
Medicare screening colonoscopy intervals include:
- G0105: once every 24 months for qualifying high-risk patients.
- G0121: once every 120 months (10 years) for qualifying average-risk patients who do not meet high-risk criteria.
- G0121 after covered screening flexible sigmoidoscopy: once 48 months after the prior screening flexible sigmoidoscopy (at least 47 months must have elapsed after the month of that procedure).
Colonoscopy After a Positive Stool Test
Since January 1, 2023, Medicare has included a qualifying follow-on colonoscopy after a positive covered noninvasive stool-based colorectal cancer screening test within the complete screening benefit.
When the follow-on colonoscopy remains screening, report the applicable G code with modifier KX. The deductible and coinsurance are waived.
If a biopsy, polypectomy, or another therapeutic procedure is performed, report the applicable CPT code with modifier PT. For qualifying converted-screening procedures in 2026, the deductible remains waived, and beneficiary coinsurance is reduced to 15%.
KX and PT are not interchangeable. KX identifies the follow-on screening circumstance; PT identifies a Medicare screening colonoscopy that becomes diagnostic or therapeutic.
When to Use CPT Code 45378?
CPT 45378 generally applies when:
- A medical indication is documented
- A diagnostic colonoscopy is performed
- No tissue biopsy or separately reportable therapeutic procedure is performed
Possible indications include bleeding, melena, chronic blood-loss anemia, bowel-habit changes, diarrhea, abnormal imaging, or documented surveillance history. Coverage depends on payer policy and documentation.
Example
A commercial-plan member reports rectal bleeding. The physician reaches the cecum, identifies internal hemorrhoids, and performs no biopsy or treatment.
CPT 45378 may be appropriate with the diagnosis that best reflects the documented bleeding. The presence of an incidental finding does not itself require a therapeutic code.
CPT Code 45378 Reimbursement Rate for 2026
For 2026, Medicare’s national payment amount for CPT code 45378 is approximately $378.10 in a non-facility setting and $164.67 in a facility setting. When an incomplete professional colonoscopy is reported with modifier 53, Medicare pays approximately $189.38 in a non-facility setting and $82.50 in a facility setting. These figures are national, geographically unadjusted professional payment amounts; actual reimbursement may vary by locality.
The national average private payer reimbursement for CPT 45378 is approximately $441.56 from Blue Cross Blue Shield, $471.77 from UnitedHealthcare, $522.30 from Aetna, and $331.18 from Cigna. These averages provide a useful benchmark, but actual commercial reimbursement depends on the provider contract, network participation, geographic market, place of service, and the payer’s current fee schedule.
What Modifiers Apply to CPT 45378?
Below are the modifiers that apply to CPT code 45378:
- PT: Medicare screening colonoscopy that becomes diagnostic or therapeutic.
- 33: Eligible preventive service on claims that require or accept the modifier.
- 52: Reduced services; not a substitute for modifier 53.
- 53: Incomplete or discontinued professional colonoscopy caused by an unforeseen circumstance.
- 73: Outpatient hospital or ASC procedure discontinued before anesthesia.
- 74: Outpatient hospital or ASC procedure discontinued after anesthesia or after the procedure begins.
- KX: Applicable Medicare follow-on screening colonoscopy after a positive covered stool-based test.
Modifier selection must reflect the payer, claim type, and documentation.
Documentation Requirements For CPT Code 45378
The report should support the code, diagnosis, modifier, medical necessity, and completeness. Document:
- Clinical indication and relevant history
- Maximum insertion depth and landmarks
- Complete or incomplete status
- Reason for stopping
- Findings
- Brushing, washing, biopsy, removal, ablation, or other intervention
- Technique and lesion location when multiple procedures are reported
“Scope advanced to the cecum; cecal landmarks identified and photographed” provides stronger support than “colonoscopy performed.”
A diagnosis should not be selected only because it appears on a coverage list. The medical record must support it.
Common ICD-10-CM Codes Used on Colonoscopy Claims
- K92.1 — Melena
- K92.2 — Gastrointestinal hemorrhage, unspecified
- K62.5 — Hemorrhage of anus and rectum
- D50.0 — Iron-deficiency anemia secondary to chronic blood loss
- R19.4 — Change in bowel habit
- R19.5 — Other fecal abnormalities
- R19.7 — Diarrhea, unspecified
- R93.3 — Abnormal digestive-tract imaging findings
- K63.5 — Polyp of colon
- Z86.0101 — Personal history of adenomatous and serrated colon polyps
- Z12.11 — Encounter for screening for malignant neoplasm of colon
- Z80.0 — Family history of malignant neoplasm of digestive organs
A diagnosis code alone does not establish medical necessity. The record must support the diagnosis and the reason for the colonoscopy.
Common CPT 45378 Billing and Coding Errors
Avoid these mistakes when submitting colonoscopy claims:
- Reporting 45378 with a therapeutic code for the same diagnostic examination
- Retaining G0105 or G0121 after a therapeutic procedure
- Omitting modifier PT from a converted Medicare screening claim
- Using modifiers KX and PT interchangeably
- Reporting modifier 53 on a facility claim
- Using modifier 52 instead of modifier 53
- Reporting an unsupported diagnosis
- Failing to document insertion depth or incomplete procedure details
- Billing brushing or washing as a tissue biopsy
Final Words
CPT 45378 reports a diagnostic flexible colonoscopy without a separately reportable biopsy or therapeutic intervention. To reduce errors, document insertion depth and landmarks. Distinguish screening, diagnostic, surveillance, and follow-on screening circumstances. Report every separately billable procedure, and do not report 45378 when it is included in therapeutic endoscopy. Apply modifiers only when their requirements are met. Verify current CMS, NCCI, ICD-10-CM, and fee-schedule instructions before claim submission.
