Code Colonoscopies With Precision (2025)

Accurate billing of these procedures requires attention to detail.

Colonoscopy is a medical procedure in which the physician inserts a long, flexible, tubular instrument called a colonoscope into the patient’s anus to examine the lining of the entire colon for abnormalities and disease conditions. This type of test may be performed as a colorectal cancer preventive screening, for surveillance reasons, or for diagnostic/therapeutic purposes. Here’s what you need to know to correctly code colonoscopies for all four encounter types.

What Type of Colonoscopy Is It?

The first detail to consider is the purpose of the encounter. Colonoscopies fall into four basic encounter types:

Screening colonoscopy is provided to a patient in the absence of signs or symptoms based on the patient’s age, gender, medical history, and family history according to medical guidelines. It is defined by the population on which the test is performed, not the results or findings of the test. As such, “screening” describes a colonoscopy that is routinely performed on an asymptomatic person for the purpose of testing for the presence of colorectal cancer or colorectal polyps.

Diagnostic colonoscopy is performed when the patient has physical symptoms such as rectal bleeding or pain and the test is necessary to either rule out or confirm a suspected condition. Signs and symptoms are used to explain the reason for the test.

Therapeutic colonoscopy is performed when the abnormalities are treated for the purpose of biopsy, tumor ablation, or other therapy.

Surveillance colonoscopy is when the patient is asymptomatic but has a personal history of gastrointestinal disease, colon polyps, or cancer. Technically, this is a screening test with different diagnostic coding and frequency guidelines.

Coding Colonoscopies

In knowing the reason for the encounter — preventive, diagnostic, therapeutic, or surveillance — you can select the appropriate procedure code based on the patient’s age, risk for colorectal cancer, and insurance (not to mention fee schedule).

Screening Colonoscopy

Medicare coverage for preventive colonoscopies applies to patients aged 50 and older. As of 2022, the majority of commercial insurances cover screening colonoscopy for patients aged 45 and older. And a few payers cover even earlier for individuals at high risk for colorectal cancer.

For commercial and Medicaid patients, report CPT® code 45378 Colonoscopy, flexible; diagnostic, including collection of specimens(s) by brushing or washing, when performed (separate procedure). Append modifier 33 Preventive service to the procedure code to trigger the preventive benefits (no cost-sharing) to the patient.

Append modifier PT A colorectal cancer screening test converted to diagnostic test or other procedure to the procedure code if a screening turned into a diagnostic procedure. This does not waive Medicare patients’ 20 percent coinsurance and/or a copay, but it will waive the deductible.

For Medicare patients, report HCPCS Level II code G0105 Colorectal cancer screening; colonoscopy on individual at high risk or G0121 Colorectal cancer screening; colonoscopy on individual not meeting criteria for high risk, as appropriate. Modifier 33 is not used on G0121 or G0105 since screening is already indicated in the code descriptions.

As you can see, you must know whether a Medicare patient is at high risk for colorectal cancer to select the right screening code. Per the Medicare Claims Processing Manual (Pub 104, Ch.18, Sec. 60), an individual at high risk for colorectal cancer has:

• A personal history of adenomatous polyps, colorectal cancer, or inflammatory bowel disease, including Crohn’s disease and ulcerative colitis; and/or
• A family history of familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer or a close relative (sibling, parent, or child) who has had colorectal cancer or an adenomatous polyp.

Note the words in bold. These Medicare guidelines are often overlooked and, if not followed, will result in claim denials. Commercial payers may allow additional levels of family history, so always check policies for non-Medicare patients.

Per the ICD-10-CM guidelines, “A screening code may be a first-listed code if the reason for the visit is specifically for the screening exam.” That code would be Z12.11 Encounter for screening for malignant neoplasm of colon. To indicate risk, code selection will depend on the documented patient history (see the Medicare Administrative Contractor’s local coverage determination for colonoscopy for a complete list of diagnosis codes indicating high risk that are applicable to G0105). To indicate a screening colonoscopy is for surveillance of a previous problem, be sure to report the applicable history code, provided it is supported in the medical record.

Another consideration is frequency. Medicare covers screening colonoscopy for patients at normal risk for colorectal cancer once every 120 months (10 years) or 48 months after a previous sigmoidoscopy and once every 24 months for patients who are at high risk and/or require surveillance after findings from a previous screening. Per Pub. 100-04, Medicare Claims Processing Manual, Ch.18, Sec. 60, start the “count beginning with the month after the month in which a previous test/procedure was performed.” In other words, if the test was performed in March, begin counting from April.

Diagnostic/Therapeutic Colonoscopy

Report CPT® code 45378 for diagnostic colonoscopy if the scope reaches to the cecum; no modifier is allowed (see Figure 1). CPT® instructs you to append modifier 53 Discontinued procedure to the code if the scope goes beyond the splenic flexure, but not all the way to the cecum. If the scope does not reach the splenic flexure, then it is considered a flexible sigmoidoscopy, reported with code 45330 Sigmoidoscopy, flexible; diagnostic, including collection of specimen(s) by brushing or washing, when performed (separate procedure). As you can see, proper coding hinges on the physician documenting that information.

If therapeutic measures, such as polyp removal, are performed, select the colonoscopy code that most accurately describes what was done. Append modifier 52 Reduced services to the code if the scope extends beyond the splenic flexure, but not as far as the cecum.

According to ICD-10-CM/PCS Coding Clinic (First Quarter 2017), whenever a screening exam is performed, the screening code is the first listed, even if an additional procedure is performed as a result of the screening. In the event a screening turns diagnostic, also code the finding(s).

Note: When submitting a claim for the facility fee associated with the procedure, ambulatory surgical centers (ASCs) should append the colonoscopy code with modifier 73 Procedure terminated/discontinued before anesthesia is provided or 74 Procedure terminated/discontinued after anesthesia is induced or the procedure is initiated, as appropriate. (See Pub. 100-04, Medicare Claims Processing Manual, Ch. 4, Sec. 20.6.4.)

Code by Example

Let’s look at a few coding examples for various colorectal cancer screening encounters.

Scenario 1:

Indication: Family history of colon cancer

Procedure performed: Screening colonoscopy

Coding: G0105, Z80.0 for Medicare patients (no cost-sharing)

45378-33, Z80.0 for Medicaid and commercial patients

Rationale: For Medicaid and commercial patients, append modifier 33 to the CPT® code to eliminate patient cost-sharing (copay, coinsurance, and deductible).

Scenario 2:

Indication: Iron deficiency anemia, screening colon

Procedure performed: Colonoscopy

Coding: 45378, D50.9, Z12.11

Rationale: Screening is always performed on asymptomatic patients. As the reason for the visit is iron deficiency anemia, the test would be considered diagnostic even though a screening colonoscopy is specified. This scenario is considered a diagnostic colonoscopy so it is coded without modifiers 33/PT and the diagnosis is sequenced before the encounter code.

Scenario 3:

Indication: Colon screening on average risk patient

Post-endoscopy findings: Polyps in the cecum and sigmoid colon

Procedure performed: Colonoscopy with removal of cecal and sigmoid polyp by snare technique

Coding: 45385-33, Z12.11, D12.0, D12.5 or K63.5 (non-Medicare)

45385-PT, Z12.11, D12.0, D12.54 or K63.5 (Medicare)

Rationale: The intent of the study was screening colonoscopy, but a polyp was removed during the procedure, which converted the screening colonoscopy to a diagnostic/therapeutic colonoscopy. Report the appropriate CPT® code with modifier 33/PT appended, depending on the payer. The screening code (Z12.11) would be sequenced first, followed by the findings. Also, once the polyp is removed, the follow-up visit should not be coded with K63.5 Polyp of colon, but rather Z86.010 Personal history of colonic polyps.

Don’t Overlook Anesthesia

In most cases, anesthesia is used when performing colonoscopies. For a screening colonoscopy, this service may be reported separately with CPT® code 00812 Anesthesia for lower intestinal endoscopic procedures, endoscope introduced distal to duodenum; screening colonoscopy (Medicare coinsurance and deductible are also waived). When a screening colonoscopy turns into a diagnostic colonoscopy, report the anesthesia service with CPT® 00811 Anesthesia for lower intestinal endoscopic procedures, endoscope introduced distal to duodenum; not otherwise specified with modifier PT. Appending modifier PT will waive the Medicare deductible but not the coinsurance. Moderate sedation is reported with HCPCS Level II code G0500 or, if warranted, CPT® code 99152-33 and 99153-33 based on time.

Can a Pre-screening Visit Be Billed?

Medicare does not cover a pre-procedure visit for a screening colonoscopy. However, a few of the commercial insurances will cover the visit with code S0285 Colonoscopy consultation performed prior to a screening colonoscopy procedure. You will need to check the payer’s policy.

Update (May 4, 2022): Please see MLN Matters article MM12656 for changes to Medicare coinsurance for additional procedures furnished during the same clinical encounter as certain colorectal cancer screening tests.

Resources:

Fletcher, TerryA. BS, CPC, CCC, CEMC, CCS, CCS-P, CMC, CMSCS, ACS-CA, SCP-CA, QMGC, QMCRC, QMPM, Gastroenterology Coding Reference Guide

cdc.gov/cancer/colorectal/basic_info/screening/index.htm

codingintel.com/coding-for-screening-colonoscopy

gastro.org/practice-guidance/reimbursement/coding-faq-screening-colonoscopy

cms.gov/medicare/prevention/prevntiongeninfo/medicare-preventive-services/mps-quickreferencechart-1.html#COLO_CAN