Medical coding plays an important role in clean claims, accurate reimbursement, and compliant healthcare billing. In gastroenterology, CPT code 45378 is commonly associated with diagnostic colonoscopy.
At first glance, the code may seem straightforward. In practice, however, colonoscopy coding can become more complicated when the physician performs a biopsy, removes a lesion, controls bleeding, or carries out another therapeutic procedure during the same encounter. Screening colonoscopies may also follow different billing requirements, especially for Medicare patients.
Understanding the 45378 CPT code description, when the code is appropriate, what documentation should support it, and how payer requirements affect billing can help medical practices reduce coding errors and prevent avoidable claim denials.
Coding and payer policies can also change over time. For a broader overview of recent coding developments, see MedIntelHub’s 2026 CPT Code Changes: What Providers Need to Know.
What Is CPT Code 45378?
CPT code 45378 is used for a diagnostic flexible colonoscopy. During the procedure, a physician passes a flexible colonoscope through the rectum to examine the colon for abnormalities.
A diagnostic colonoscopy may help identify conditions or findings such as:
- Polyps
- Tumors or suspicious lesions
- Gastrointestinal bleeding
- Inflammation
- Structural abnormalities
- Other disorders involving the colon
The Centers for Medicare & Medicaid Services (CMS) explains that colonoscopy allows direct visualization of the lower gastrointestinal tract and can be used to identify polyps, tumors, and other intestinal lesions.
More information is available in the CMS Billing and Coding: Colonoscopy and Sigmoidoscopy-Diagnostic article.
Certain basic diagnostic activities may be part of the examination. However, if the physician performs a separately reportable procedure, such as a biopsy or a specific lesion-removal technique, another colonoscopy code may be more appropriate.
For that reason, medical code 45378 should not automatically be assigned to every colonoscopy encounter.
CPT 45378 Description and Purpose
The CPT 45378 description generally refers to a diagnostic examination of the colon using a flexible colonoscope.
Its main purpose is to allow the physician to inspect the colon and determine whether abnormal findings are present. A diagnostic colonoscopy may be ordered because a patient has symptoms, an abnormal test result, a previous gastrointestinal condition, or another medically supported reason.
Common reasons for performing a diagnostic colonoscopy may include:
- Rectal or gastrointestinal bleeding
- Persistent changes in bowel habits
- Unexplained gastrointestinal symptoms
- Abnormal imaging or laboratory findings
- Suspected inflammatory bowel disease
- Previous colorectal abnormalities
- Follow-up or surveillance after certain previous findings or treatments
The presence of one of these circumstances does not automatically guarantee insurance coverage. The patient’s medical record should support the reason for the procedure, and individual payers may apply their own medical-necessity requirements.
CMS guidance states that documentation should support the medical reasonableness, necessity, and frequency of a diagnostic colonoscopy.
When Is Procedure Code 45378 Used?
Procedure code 45378 is generally used when a diagnostic colonoscopy is performed and the encounter does not involve another more specific colonoscopy procedure that changes the final coding.
One of the most important coding principles is simple: code what was actually performed, not merely what was originally scheduled.
Consider a patient who is scheduled for a diagnostic colonoscopy. During the examination, the physician discovers a lesion and performs a biopsy. In that situation, the billing team should review the completed procedure report before selecting the final procedure code.
Assigning 45378 CPT simply because “colonoscopy” appears on the schedule can result in inaccurate coding.
The final procedure report should help the coder determine:
- Whether the colonoscopy was completed
- How far the colonoscope was advanced
- What findings were identified
- Whether specimens were collected
- Whether a biopsy was performed
- Whether a lesion or polyp was removed
- Whether bleeding was treated
- Whether any other therapeutic procedure took place
The details of the completed service should drive final code selection.
Billing Guidelines for CPT Code 45378
Billing CPT code 45378 correctly involves more than simply entering the procedure code on a claim.
Before submitting the claim, medical billers and coders should review the complete procedure report, the reason for the colonoscopy, any additional services performed, diagnosis information, modifiers, and payer-specific requirements.
Review the Final Procedure Report
The completed colonoscopy report should be the primary source used for final code selection.
Scheduling records and authorization documents may indicate what the physician intended to perform, but the actual procedure can change once the examination begins.
For example, a diagnostic procedure may become therapeutic if the physician identifies and removes a lesion.
Coding should reflect the completed encounter.
Determine Why the Colonoscopy Was Performed
The billing team should establish whether the colonoscopy was:
- Diagnostic
- Screening
- Surveillance-related
- Performed because of symptoms
- Performed following abnormal test results
This distinction can affect procedure coding, diagnosis coding, modifiers, insurance coverage, and patient cost-sharing.
Check for Additional Procedures
A diagnostic examination is generally considered part of a more extensive endoscopic service performed during the same encounter.
CMS maintains the National Correct Coding Initiative (NCCI) to reduce inappropriate reporting of services that should not be billed separately.
The current Medicare NCCI Policy Manual includes guidance for digestive-system procedures and endoscopic services.
See the 2026 Medicare NCCI Policy Manual, Chapter 6 for additional Medicare coding guidance.
When more than one colonoscopy procedure is documented during the same encounter, coders should review current CPT instructions, NCCI edits, and the patient’s payer policies before reporting multiple codes.
Verify Payer Requirements
A valid CPT code does not automatically guarantee reimbursement.
Medicare, Medicaid programs, Medicare Advantage plans, and commercial insurers may have different requirements involving:
- Medical necessity
- Covered diagnoses
- Prior authorization
- Modifiers
- Frequency limitations
- Place of service
- Screening benefits
- Patient eligibility
- Claim edits
A procedure may be coded correctly and still be denied if the payer’s coverage requirements are not satisfied.
For more information about how coding changes interact with documentation and payer rules, MedIntelHub’s 2026 CPT code changes guide provides additional background.
Documentation Requirements for CPT 45378
Complete documentation is one of the most important elements supporting the 45378 CPT code.
CMS guidance for diagnostic colonoscopy states that the medical record should support the medical reasonableness, necessity, and frequency of the diagnostic service. Documentation should also identify the areas examined and the depth reached during the procedure.
A separate CMS article addressing diagnostic and therapeutic colonoscopy notes that procedure documentation should include the maximum depth reached, abnormal findings, and any procedures performed because of those findings.
See CMS Billing and Coding: Diagnostic and Therapeutic Colonoscopy.
A well-documented colonoscopy report should generally make clear:
- Why the procedure was performed
- The extent of the examination
- Relevant normal and abnormal findings
- Whether the examination was completed
- Whether specimens were collected
- Whether a biopsy was performed
- Whether a lesion or polyp was removed
- Whether bleeding was treated
- Any other therapeutic procedures performed
- Why the procedure was stopped, if it could not be completed
Documentation should describe what actually occurred during the encounter. It should never be altered merely to support a preferred billing code.
It is also important to distinguish documentation requirements from claim-submission requirements. Supporting medical records generally need to be maintained and made available when requested; they are not automatically submitted with every routine claim.
The CPT code 45378 description becomes easier to understand when it is compared with other commonly used colonoscopy codes.
| Code | General Use |
|---|---|
| 45378 | Diagnostic flexible colonoscopy |
| 45380 | Colonoscopy involving biopsy |
| 45381 | Colonoscopy involving submucosal injection |
| 45382 | Colonoscopy involving control of bleeding |
| 45384 | Colonoscopy involving certain lesion-removal techniques |
| 45385 | Colonoscopy involving lesion removal with a snare |
These codes should not be selected simply because a particular technique or finding is mentioned somewhere in the patient’s medical record.
The completed procedure documentation must support the service being reported.
For example, if the physician discovers a polyp and removes it using a snare, reporting only CPT 45378 may not accurately describe the procedure that was performed.
Likewise, basic specimen collection during a diagnostic examination should not automatically be treated as a separately reportable biopsy.
When determining the appropriate code or combination of codes, billing professionals should consult the current CPT code set, official coding instructions, NCCI edits, and payer-specific guidance.
The American Medical Association maintains the CPT code set and offers general CPT information through its CPT code set quick reference guide.
Diagnostic Colonoscopy vs. Screening Colonoscopy
Another common source of confusion is the difference between a diagnostic colonoscopy and a screening colonoscopy.
A diagnostic colonoscopy is generally performed because the patient has symptoms, abnormal findings, or another medical reason requiring further evaluation.
A screening colonoscopy, on the other hand, is performed as a preventive service to detect colorectal cancer or precancerous abnormalities in eligible patients who meet the relevant screening criteria.
Under Medicare, certain screening colonoscopies are reported using HCPCS codes such as G0105 and G0121, depending on the patient’s circumstances.
That means billing staff should not assume that every screening colonoscopy should be reported with CPT code 45378.
CMS also expanded its definition of complete colorectal cancer screening effective January 1, 2025, to include certain follow-on screening colonoscopies performed after positive covered noninvasive colorectal cancer screening tests.
More information about Medicare preventive services is available through the CMS Preventive Services resource.
Before submitting a claim, the billing team should review:
- The reason for the colonoscopy
- Whether the procedure was screening or diagnostic
- The patient’s screening history
- Findings during the procedure
- Any additional services performed
- Applicable payer coverage rules
What Happens When a Colonoscopy Cannot Be Completed?
Sometimes a physician begins a colonoscopy but cannot advance the scope to the required anatomical endpoint because of unforeseen circumstances.
CMS considers this an incomplete colonoscopy.
For applicable Medicare claims involving an attempted diagnostic colonoscopy, CMS guidance states that CPT 45378 may be reported with modifier 53 when the procedure cannot be completed because of qualifying circumstances.
The modifier is appended to the procedure code, not to the diagnosis.
For further details, see CMS Billing and Coding: Incomplete Colonoscopy/Failed Colonoscopy.
The medical record should clearly document:
- Why the colonoscopy could not be completed
- How far the colonoscope advanced
- Relevant clinical or anatomical circumstances
- What services were performed before the procedure was discontinued
Commercial payer policies may differ from Medicare rules, so modifier requirements should always be verified with the patient’s insurer.
CPT Code 45378 and Medical Necessity
Medical necessity is another important consideration when billing CPT 45378.
Even when the procedure code accurately reflects the service performed, the claim may still be denied if the payer determines that its coverage criteria were not met.
CMS diagnostic colonoscopy guidance emphasizes that the medical record should substantiate both the diagnosis reported on the claim and the medical need for the procedure.
Diagnosis coding should therefore reflect the documented reason the colonoscopy was performed.
Billing teams should avoid:
- Selecting a diagnosis only because it appears on a payer’s coverage list
- Reporting conditions that are not documented by the provider
- Using greater specificity than the medical record supports
- Changing a diagnosis solely to obtain reimbursement
Coding should always reflect the actual documentation.
Common CPT 45378 Billing Mistakes
Even experienced medical billing teams can encounter problems with medical code 45378. The following errors are among the most important to watch for.
1. Automatically Billing 45378 for Every Colonoscopy
CPT 45378 does not apply to every colonoscopy encounter.
If a physician performs a biopsy, lesion removal, injection, bleeding-control procedure, or another separately reportable service, the final coding may change.
2. Coding Before Reviewing the Final Procedure Report
The procedure that was originally scheduled may not be the same procedure that was ultimately performed.
Final coding should be based on completed documentation.
3. Confusing Diagnostic and Screening Colonoscopy
Screening colonoscopies may have different procedure codes, modifiers, coverage requirements, and cost-sharing rules.
The reason for the examination should be established before the claim is submitted.
4. Failing to Document the Extent of the Examination
How far the colonoscope was advanced can be important when determining whether the colonoscopy was complete.
The procedure report should clearly document the extent of the examination.
5. Reporting Multiple Colonoscopy Codes Incorrectly
When several services are performed during one encounter, CPT instructions and NCCI edits may affect whether the procedures can be separately reported.
Coders should review applicable bundling rules before submitting the claim.
6. Overlooking Modifier Requirements
An incomplete colonoscopy or another unusual circumstance may require a modifier under applicable payer rules.
Modifiers should be supported by the documentation.
7. Assuming a Valid CPT Code Guarantees Payment
Correct coding and insurance coverage are related, but they are not the same thing.
A payer may require medical necessity, prior authorization, an eligible diagnosis, appropriate frequency, or another condition before reimbursement is issued.
Tips for Accurate CPT 45378 Billing
A consistent claim-review process can reduce preventable errors and unnecessary denials.
Before submitting a claim involving CPT code 45378, billing teams should:
- Review the completed colonoscopy report.
- Confirm the reason the procedure was performed.
- Determine whether the service was diagnostic or screening.
- Check whether a biopsy or therapeutic procedure occurred.
- Verify the maximum depth reached during the examination.
- Determine whether the procedure was completed.
- Match the diagnosis code to the documented reason for the service.
- Review applicable modifier requirements.
- Check current NCCI edits when multiple procedures are reported.
- Verify payer-specific coverage and authorization requirements.
- Use the current CPT code set and coding guidance.
- Periodically review colonoscopy denials to identify recurring workflow problems.
These steps can help practices reduce undercoding, incorrect code combinations, denials, and unnecessary claim corrections.
Frequently Asked Questions
What is CPT code 45378 used for?
CPT code 45378 is generally used to report a diagnostic flexible colonoscopy when the physician examines the colon and the completed procedure is appropriately represented by the diagnostic colonoscopy code.
What does the 45378 CPT code description mean?
The 45378 CPT code description refers to a diagnostic examination of the colon using a flexible colonoscope. If the physician performs certain therapeutic procedures during the examination, a different or additional coding approach may be required.
Is CPT 45378 used for a colonoscopy with biopsy?
CPT 45378 is not the specific colonoscopic biopsy code. When a biopsy is performed and applicable coding requirements are met, a code such as CPT 45380 may be relevant.
What is the difference between CPT 45378 and 45380?
CPT 45378 generally represents diagnostic colonoscopy, while CPT 45380 is associated with a colonoscopy in which a biopsy is performed. Final code selection should be based on the physician’s procedure documentation and current coding guidelines.
Can CPT 45378 be used for a screening colonoscopy?
Not in every situation. Screening colonoscopies may follow different coding requirements, particularly under Medicare. Medicare uses specific HCPCS codes for qualifying screening colonoscopies.
Can modifier 53 be used with CPT 45378?
Under Medicare guidance, modifier 53 may be appended to CPT 45378 when a covered diagnostic colonoscopy is attempted but cannot be completed because of qualifying unforeseen circumstances.
Is procedure code 45378 covered by Medicare?
Medicare may cover a medically necessary diagnostic colonoscopy when applicable coverage requirements are met. Documentation, diagnosis coding, medical necessity, and other Medicare requirements can affect claim payment.
Does CPT 45378 include polyp removal?
CPT 45378 represents the diagnostic colonoscopy. If a polyp or lesion is removed using a separately reportable technique, another colonoscopy procedure code may apply.
Prior authorization requirements vary by payer and health plan. Some commercial insurers and managed-care plans may require authorization for certain colonoscopy services, while others may not. Eligibility and authorization should be confirmed before the procedure when required.
Conclusion
Understanding the CPT code 45378 description is important for medical coders, billing professionals, gastroenterology practices, and healthcare administrators.
CPT 45378 is generally associated with diagnostic flexible colonoscopy, but accurate coding depends on what actually occurs during the examination.
If the physician performs a biopsy, removes a lesion, controls bleeding, performs an injection, or carries out another therapeutic procedure, a different coding approach may be necessary.
Before submitting a claim, billing teams should review the final procedure report, confirm medical necessity, distinguish between diagnostic and screening services, apply appropriate modifiers, and verify payer-specific requirements.
Most importantly, procedure code 45378 should not be treated as a universal code for every colonoscopy.
Accurate reimbursement starts with documentation and coding that clearly reflect the service actually performed.
Resources
For additional information about CPT code 45378, colonoscopy documentation, Medicare billing requirements, and correct coding policies, the following resources can be useful.
Centers for Medicare & Medicaid Services — Diagnostic Colonoscopy
CMS provides guidance on diagnostic colonoscopy, documentation requirements, medical necessity, and Medicare billing considerations.
CMS: Billing and Coding — Colonoscopy and Sigmoidoscopy-Diagnostic
CMS — Diagnostic and Therapeutic Colonoscopy
This CMS resource provides additional guidance on documentation, coding, incomplete procedures, and medical necessity for diagnostic and therapeutic colonoscopy services.
CMS: Billing and Coding — Diagnostic and Therapeutic Colonoscopy
CMS — Incomplete Colonoscopy
CMS explains how Medicare handles colonoscopies that cannot be completed and provides guidance concerning modifier 53.
CMS: Incomplete Colonoscopy/Failed Colonoscopy
CMS — National Correct Coding Initiative
The NCCI program provides Medicare coding policies and procedure-to-procedure edits that can affect whether multiple services may be reported separately.
CMS National Correct Coding Initiative
CMS — 2026 NCCI Policy Manual
Chapter 6 of the Medicare NCCI Policy Manual covers digestive-system procedures and includes guidance relevant to endoscopic services.
2026 Medicare NCCI Policy Manual — Chapter 6
American Medical Association — CPT Resources
The AMA develops and maintains the CPT code set. Healthcare professionals should consult the current licensed CPT codebook or another authorized CPT resource when making final coding decisions.
AMA CPT Code Set Quick Reference Guide
MedIntelHub — 2026 CPT Code Changes
MedIntelHub’s 2026 CPT guide covers recent coding updates, payer considerations, documentation issues, and other developments affecting healthcare billing.
2026 CPT Code Changes: What Providers Need to Know
MedIntelHub — Editorial Policy
Readers can review MedIntelHub’s approach to healthcare content, sourcing, editorial standards, and transparency.
Editorial Disclaimer
This article is provided for educational and informational purposes only. CPT coding requirements, Medicare policies, commercial payer rules, coverage criteria, reimbursement requirements, and documentation standards may change and can vary by payer, jurisdiction, place of service, provider type, and individual circumstances.
CPT is a registered trademark of the American Medical Association.
This article does not replace the current CPT codebook, official CPT guidelines, CMS instructions, Medicare Administrative Contractor policies, commercial payer guidance, or advice from a qualified medical coding or compliance professional.
Healthcare providers and billing teams should verify current coding, billing, and coverage requirements before submitting claims.
David Bennett
David Bennett is an author at MedIntelHub, where he creates clear, practical, and well-researched content about healthcare, medical billing, insurance, and patient education. His goal is to make complex healthcare topics easier for readers to understand and use in everyday situations. David emphasizes accuracy, transparency, and reliable sourcing, using information from trusted organizations and official healthcare resources whenever possible. Content published by David is intended for educational purposes and should not replace advice from qualified medical, legal, or healthcare professionals.