Gastroenterology Coding Alert

Find out where you won’t find clear guidance.

Correctly coding colorectal cancer (CRC) screenings is essential for ensuring proper reimbursement, preventing unexpected patient costs, and satisfying payer requirements.

With two-year old policy changes — especially the Centers for Medicare & Medicaid Services (CMS) updates in the 2023 Medicare Physician Fee Schedule (MPFS) and other Medicare/HCPCS policy changes — coders must understand when to report screening versus diagnostic services, which patients qualify for low- or high-risk screenings, when modifiers apply, and which ICD-10-CM codes support medical necessity.

In this final article of the two-part series, Revenue Cycle Insider breaks down the necessary ICD-10-CM codes and highlights the areas still under debate.

Note: Read Part 1 to catch up on the series.

Learn What Happens When a Screening Becomes Diagnostic or Therapeutic

If a screening colonoscopy transitions mid-procedure because the doctor removes a polyp or other lesion, report the diagnostic/therapeutic CPT^® code and append modifier PT (Colorectal cancer screening test converted to a diagnostic test or other procedure).

Example: The physician removes a Medicare patient’s polyp using snare technique. For this procedure, you’ll report 45385 (Colonoscopy, flexible; with removal of tumor(s), polyp(s), or other lesion(s) by snare technique) appended with PT.

Some commercial payers reject PT and require modifier 33 (Preventive services) instead. Also, note that if no polyp is removed but there is a finding of something benign (e.g., diverticulosis) the screening does not convert to therapeutic, so you won’t append modifier PT.

Important: Not all diagnostic findings change the service. Incidental diverticulosis does not convert a screening to a therapeutic procedure. In this case, modifier PT does not apply.

Understand the Accurate Use of Procedural Codes

Providers may use “diagnostic” and “therapeutic” interchangeably, but here’s what the definitions mean:

• Diagnostic: A procedure performed to evaluate symptoms
• Therapeutic:  A finding during a screening that results in treatment (e.g., polyp removal)

The CPT^® code set is the same, but modifier logic and payer policy differ.

Common coding pitfall: You can only separately report 45382 (Colonoscopy, flexible; with control of bleeding, any method) when the provider does not cause the bleeding. If the provider’s biopsy causes bleeding, control of bleeding is bundled into the primary procedure.

Assign ICD-10-CM Codes to Show Medical Necessity

The ICD-10-CM guidance is not necessarily clear when it comes to colorectal cancer screening, so you will need to choose your diagnosis codes carefully.

Your screening diagnosis codes are as follows:

• Z12.11 (Encounter for screening for malignant neoplasm of colon), which is the primary diagnosis for all true screening colonoscopies, and
• Z12.12 (Encounter for screening for malignant neoplasm of rectum) if the exam is for the rectum specifically. 

Suppose the patient has a positive stool test and then undergoes a follow-up colonoscopy. In this scenario, your ICD-10-CM sequencing would be as follows:

• Z12.11 for the screening
• Finding code (if known), such as K63.5 (Polyp of colon)
• R19.5 (Other fecal abnormalities) to show reason for follow-up

Note: Payer policies vary, and some may require other codes (e.g., Z83.71- [Family history of colonic polyps] or Z80.0 [Family history of malignant neoplasm of digestive organs]) as secondary. 

What about surveillance diagnoses? An example includes Z86.010- (Personal history of colon polyps). Be aware that Medicare treats surveillance as a screening. In other words, you would use G0105 (Colorectal cancer screening; colonoscopy on individual at high risk) for individuals who are high risk, which may include history of polyps or cancer, but the intent must still be screening (not diagnostic). If symptoms are present or the exam is purely surveillance (i.e., prior finding), payer specifics may differ. Commercial payers often require you to report 45378 (Colonoscopy, flexible; diagnostic, including collection of specimen(s) by brushing or washing, when performed (separate procedure)) with modifier 33 and still impose cost-sharing due to the Z86.010- history code.

Find Out What Areas Are Still Up for Debate

Some areas of coding are still not crystal clear, and they include the following areas:

• While no official ICD-10-CM guideline or CMS rule dictates a fixed sequencing for a colonoscopy following a positive stool-based test, industry guidance (e.g., the American Gastroenterological Association [AGA]) recommends using Z12.11 first, then R19.5 and any finding code.
• There is not uniform payer acceptance of modifiers PT and 33. Medicare requires PT; commercial payers vary widely.
• There is not uniform commercial payer cost-sharing policies for surveillance colonoscopy. Many still assess a copay/deductible when history codes like Z86.010- apply.
• There is not a final adoption timeline for cost-sharing elimination (though Medicare’s phase-out dates are set, commercial payer policies may lag or vary).
• Coverage of CT colonography (74263 [Computed tomographic (CT) colonography, screening, including image postprocessing]) under Medicare beginning Jan. 1, 2025, is another evolving area.

Conclusion

Correct CRC screening coding requires close attention to payer rules, modifier requirements, and documentation of risk status. The 2023 CMS updates — lowering the screening age and expanding preventive coverage to stool-test-positive follow-ups — significantly reduced patient cost exposure.

However, a lack of finalized ICD-10-CM sequencing and inconsistencies among commercial payers still create challenges. By coding exactly as the provider ordered, applying modifiers correctly, and sequencing diagnoses according to emerging guidance, you can reduce denials, protect patients from unexpected costs, and ensure full compliance.

Suzanne Burmeister, BA, MPhil, Medical Writer and Editor