Colonoscopy Coding for Medicare

How likely is it that a screening colonoscopy becomes diagnostic? It turns out that the answer depends on several factors—your age at the time of your first colonoscopy, your gender, and your family history. On average, about half of people will have a completely normal first screening. That means the other half may have findings that shift the procedure from purely screening to diagnostic. Let’s explore what that means and why it matters.

Medicare Coverage

Medicare provides specific guidelines for coding screening colonoscopies, which are essential for ensuring accurate billing and patient coverage.

For patients at average risk, the procedure is billed using HCPCS code G0121, while those at high risk—such as individuals with a family history of colorectal cancer—are billed under G0105.

These screenings are typically covered without cost-sharing:

every 10 years for average-risk patients, and

every 2 years for high-risk individuals

The diagnosis code Z12.11 is used to indicate the screening nature of the visit, and additional codes like Z80.0 may be added for high-risk patients.

However, if a screening colonoscopy transitions into a diagnostic procedure—such as when a polyp is found and removed—the coding must reflect this change. In these cases, the appropriate CPT code for the procedure performed (e.g., 45385 for polypectomy) is used, and the -PT modifier is appended to indicate that the service began as a screening. Intent is key here.

This distinction is crucial because, while Medicare waives the deductible, the patient may still be responsible for coinsurance. Both the screening diagnosis (Z12.11) and the diagnostic finding (e.g., D12.6 for a benign neoplasm) should be reported.

How do we handle asymptomatic patients referred for screening?

Regarding pre-screening E/M visits, Medicare does not cover a separate Evaluation and Management (E/M) service solely for scheduling a screening colonoscopy in asymptomatic patients. If the patient is seen for another medically necessary reason and the colonoscopy is discussed during that visit, the E/M service may be billed with a -25 modifier, provided it is a separately identifiable service. Understanding these nuances ensures compliance with Medicare rules and helps avoid billing errors that could impact reimbursement or patient costs.

How do we code for Screening Colonoscopy?

HCPCS Codes:

G0105 – Screening colonoscopy for individuals at high risk.
G0121 – Screening colonoscopy for individuals not at high risk.

ICD-10 Diagnosis Codes:

Z12.11 – Encounter for screening for malignant neoplasm of colon.
Z80.0 – Family history of malignant neoplasm of digestive organs (used for high-risk patients).

Frequency Limits:

High-risk patients: Once every 24 months.
Average-risk patients: Once every 120 months (10 years), or 48 months after a flexible sigmoidoscopy.

What do we do when Screening Colonoscopy Becomes Diagnostic?

If a screening colonoscopy identifies a condition requiring biopsy, polyp removal, or other interventions, it is converted to diagnostic.

Steps for Coding:

Use the CPT code for the specific procedure(s) performed (e.g., 45385 for polyp removal).
Append Modifier -PT to indicate the procedure began as a screening but became diagnostic.
Use both ICD-10 codes:
- Z12.11 (screening intent)
- Plus, the diagnosis code for the condition found (e.g., D12.6 for benign neoplasm of colon).

How does this affect billing?

Medicare waives the deductible, but coinsurance may apply when a screening becomes diagnostic.

Screening Colonoscopy Coding Examples:

Example 1: Average-Risk Screening

Patient: 68-year-old, no symptoms, average risk.
Code: G0121
Diagnosis: Z12.11
Modifiers: None
Billing: Deductible and coinsurance waived.

Example 2: High-Risk Screening

Patient: 55-year-old with family history of colon cancer.
Code: G0105
Diagnosis: Z80.0 and Z12.11
Billing: Deductible and coinsurance waived.

**Example 3: Screening Turns Diagnostic**

Patient: 70-year-old, average risk, polyp found and removed.
Code: 45385 (polypectomy)
Diagnosis: Z12.11 and D12.6
Modifier: -PT (Medicare)
Billing: Deductible waived, coinsurance applies.

Example 4: Pre-Screening E/M Visit (Asymptomatic patient)

Patient: 66-year-old, asymptomatic, referred to schedule screening colonoscopy.
Code: No E/M billed (not covered by Medicare).
Colonoscopy Code: G0121
Diagnosis: Z12.11

What happens if the Screening Colonoscopy is Incomplete?

Novitas says –

“Note: When a covered colonoscopy is next attempted and completed, Medicare will pay according to the payment methodology for this procedure as long as coverage conditions are met. This policy is applied to both screening and diagnostic colonoscopies.”

So, what does this mean?

Medicare Will Pay for the Follow-Up Colonoscopy:
- If the initial colonoscopy was incomplete (e.g., due to poor prep or patient intolerance) and Modifier 53 was used appropriately,
- Then the next attempted and completed colonoscopy will be covered by Medicare,
- As long as it meets the usual coverage criteria (e.g., age, frequency, medical necessity).
No Frequency Penalty:
- The follow-up colonoscopy is not subject to frequency limitations that would normally apply to screening colonoscopies (e.g., once every 10 years),
- Because the first attempt was not completed and therefore does not count as a full screening.
However – Cost-Sharing Rules Change:
- The initial incomplete colonoscopy (if coded as a screening with Modifier 53) is not subject to coinsurance or deductible under preventive care rules.
- But the follow-up colonoscopy is not considered a screening under CMS policy—even if the intent remains preventive.
- Therefore, Modifier PT should not be used, and cost-sharing (coinsurance/deductible) may apply to the follow-up procedure

CMS – Follow-up Colonoscopy Scenario:

Initial colonoscopy: Screening attempt, scope reaches only sigmoid due to poor prep code 45378-53.
Follow-up colonoscopy: Per CMS, billed as diagnostic (e.g., 45378), no Modifier PT, even if intent is still screening.
Rationale:
- CMS does not consider the completed follow-up colonoscopy as “screening” service.

In Summary, coding for screening colonoscopy can be tricky. If you have questions, please feel free to reach out to [email protected] or [email protected].