Specialty
Gastroenterology billing services
Gastroenterology billing services turn on a question asked at every colonoscopy: is this screening, surveillance or diagnostic, and what happens to the claim when a screening finds a polyp?
See where claims are getting stuck. No patient data needed.
Medicare answers with its own screening codes, intervals that depend on risk, a modifier for a screening that becomes therapeutic, another for a colonoscopy that follows a positive stool test, and a coinsurance rule that changes by year. Commercial plans answer with their own preventive code lists and age bands. Remitwright gives gastroenterology practices a dedicated biller who settles the screening question before the claim leaves and works denials back to the cause.
Gastroenterology billing is one of Remitwright's specialty billing services, each set out with its own code families, denial reasons and payer rules.
Last reviewed by the Remitwright billing team. Editorial policy
- 43235-43259
- 45330-45350
- 45378-45398
Denials
Why gastroenterology claims get denied
The reasons that come up most on gastroenterology remittances, with the usual cause and the fix. Code explanations are our own; the official list is maintained by X12.
| Code | Reason | Usual cause | The fix |
|---|---|---|---|
| CO-119 | Benefit maximum or frequency reached | An average-risk screening billed inside 120 months of the last one, a high-risk screening inside 24 months, a stool test inside 12 months or a stool DNA test inside 3 years, with no KX to show the colonoscopy followed a positive stool test | The last screening date and type pulled at eligibility, the interval checked before scheduling, and KX applied when the stool test result is in the chart |
| PR-2 | Coinsurance charged on a screening | A screening that found a polyp billed with the diagnostic code and no PT, or a screening billed with 45378 and a screening diagnosis instead of the G code, so the patient is billed the full share | Scenario logic in charge entry: G code for a clean screening, diagnostic code plus PT when tissue is removed, 33 on the sedation line |
| CO-97 | Included in another service | A diagnostic colonoscopy billed with the therapeutic one, a sigmoidoscopy with a colonoscopy at the same encounter, control of bleeding with the polypectomy that caused it, or fluoroscopy with any endoscopy | NCCI procedure-to-procedure edits run before release, with 59 or XS reserved for separate lesions and separate encounters |
| CO-4 | Procedure inconsistent with the modifier | PT on the G code instead of the diagnostic code, 33 on G0105 or G0121, or KX with no stool test on record | Modifier placement set by scenario in the scrubber, and the stool test date captured with the referral |
| CO-50 | Not medically necessary for the diagnosis | A surveillance colonoscopy after prior polyps billed with the average-risk screening diagnosis, or a diagnostic colonoscopy for symptoms billed with a screening code | Indication captured at scheduling as screening, high-risk screening, surveillance or diagnostic, and diagnosis sequencing set from it |
| CO-197 | Precertification or site review absent | A colonoscopy scheduled in a hospital outpatient department when the commercial plan requires a site-of-service review, or a CT colonography or biologic infusion without the plan's authorization | Site and authorization checked at scheduling against the plan's policy, and the approved site carried to the claim |
Codes
Common gastroenterology codes and modifiers
Code families by number with our own one-line explanations. CPT descriptors belong to the AMA and are not reproduced here.
| Codes | What the family covers |
|---|---|
| 43235-43259 | Upper endoscopy and its therapeutic variants, with washings, intubation and fluoroscopy folded into the endoscopy code |
| 45330-45350, G0104 | Flexible sigmoidoscopy, diagnostic and therapeutic, plus Medicare's screening sigmoidoscopy code, which runs on its own interval |
| 45378-45398 | Diagnostic and therapeutic colonoscopy, from the plain examination to biopsy, snare polypectomy, control of bleeding and stent placement, with one code per technique rather than one per polyp |
| 82270, G0328, 81528, G0327 | Stool blood tests, the multitarget stool DNA test and the blood-based biomarker test, each with its own Medicare interval and age band, and each a trigger for a follow-on screening colonoscopy when positive |
| 96365-96417 with J codes | Infusion of biologics for inflammatory bowel disease, timed administration codes plus the drug line, with the drug's own authorization, units and interval |
| 99153, G0500 | Moderate sedation by the endoscopist, generally separately reportable, with cost sharing on a screening claim set by whether modifier 33 or PT is attached |
| 99202-99215 | Office visits, separately payable with a same-day procedure only with modifier 25; a pre-procedure consultation has its own row in some plans' preventive policies |
| G0105, G0121 | Medicare's screening colonoscopy codes for high-risk and average-risk patients, replaced by the diagnostic or therapeutic colonoscopy code with modifier PT when tissue is found and removed |
Modifiers that matter
- PT
- A screening colonoscopy or sigmoidoscopy that became diagnostic or therapeutic because tissue was found. The diagnostic code is billed instead of the G code, PT tells Medicare it started as a screening, the deductible is waived and the reduced coinsurance applies.
- KX
- A screening colonoscopy that follows a positive non-invasive stool-based test, for dates of service from January 1, 2023. KX on the G0105 or G0121 claim tells Medicare to skip the frequency edit and waive cost sharing.
- 33
- A preventive service under commercial plan rules, and on Medicare claims the marker on moderate sedation (99153 or G0500) furnished with a screening colonoscopy so that coinsurance and deductible are waived. Not placed on the G codes themselves.
- 53
- A colonoscopy stopped for extenuating circumstances before completion. Medicare pays the professional claim at a rate built from half the inputs and does not count it against the screening frequency; surgery centers use 73 or 74 instead.
- 59 or XS
- A biopsy of one lesion (45380) and snare removal of a different lesion (45385) at the same colonoscopy. The same lesion gets one code. Separate encounters on the same day use 59 or XE.
- 51
- A second endoscopic procedure at the same session that no single code describes together with the first, such as endoscopy of the biliary tree by two different methods; the lesser procedure carries 51.
Payers
Payer notes
- MedicareThere is no deductible or coinsurance for stool tests, screening sigmoidoscopy (G0104) or screening colonoscopy (G0105, G0121). When a screening becomes diagnostic or therapeutic, the diagnostic code is billed with modifier PT, the deductible stays waived and coinsurance is reduced to 15 percent for dates of service in 2023 through 2026, 10 percent in 2027 through 2029, and waived from January 1, 2030. From January 1, 2023 a screening colonoscopy that follows a positive stool-based test is billed with modifier KX, the frequency limit does not apply and cost sharing is waived. An interrupted colonoscopy is billed with modifier 53 and paid at a rate built from half the inputs, and the frequency edit is not applied to it. The high-risk colonoscopy (G0105) is covered once every 24 months, the stool blood test once every 12 months, and screening sigmoidoscopy every 48 months or 119 months after a screening colonoscopy for a patient not at high risk.1
- MedicareHigh risk, for the 24 month colonoscopy interval, means a close relative (sibling, parent or child) with colorectal cancer or an adenomatous polyp, a family history of familial adenomatous polyposis or hereditary nonpolyposis colorectal cancer, a personal history of adenomatous polyps or colorectal cancer, or inflammatory bowel disease including Crohn's disease and ulcerative colitis.1
- MedicareScreening colonoscopy is covered once every 24 months for a patient at high risk, otherwise once every 120 months or 48 months after a screening flexible sigmoidoscopy, with no minimum age. The patient pays nothing when the provider accepts assignment. If a polyp or other tissue is removed during the screening, the patient pays 15 percent of the approved amount for the provider's services plus facility coinsurance in a hospital or surgery center. A colonoscopy after a positive stool-based or blood-based screening test is covered as a screening.2
- MedicareThe multitarget stool DNA test is covered every 3 years for patients aged 45 to 85 who have no symptoms of colorectal disease and are at average risk, with no personal or family history of the listed conditions, and the patient pays nothing when the provider accepts assignment.3
- MedicareThe blood-based biomarker screening test is covered once every 3 years for patients aged 45 to 85 with no symptoms, no personal history of adenomatous polyps, colorectal cancer or inflammatory bowel disease and no family history of colorectal cancer, at no cost when the provider accepts assignment, and a positive result is followed by a colonoscopy covered as a screening.4
- MedicareThe CY 2023 Physician Fee Schedule final rule lowered the minimum age for the age-limited colorectal screening tests from 50 to 45 and defined a complete screening as the stool-based test plus the follow-on screening colonoscopy after a positive result, so that cost sharing does not apply to either.5
- MedicareThe CY 2025 Physician Fee Schedule final rule removed barium enema as a screening method and added CT colonography and the blood-based biomarker test to the screening continuum, with a follow-on screening colonoscopy after a positive blood test carrying no beneficiary cost sharing.6
- Medicare (national coverage determination 210.3)Medicare covers one screening stool blood test per year from age 45. A blood-based biomarker test qualifies every 3 years for patients aged 45 to 85 at average risk only if it has FDA market authorization and meets the determination's thresholds: sensitivity of at least 90 percent with specificity of at least 87 percent, or sensitivity of at least 79 percent with specificity of at least 90 percent. The patient is to be told about the test's performance and the importance of a follow-on colonoscopy after a positive result.7
- Medicare and commercial plans that apply NCCIA diagnostic endoscopy is not billed with a surgical endoscopy at the same encounter, and when a single code covers everything done, only that code is billed. The same procedure performed several times in one region, such as several polypectomies by one technique, is one unit. A biopsy of one lesion and snare removal of another (45380 with 45385) can be billed together with modifier 59 or XS; the same lesion cannot. Control of bleeding caused by the procedure is included, a sigmoidoscopy completed before a colonoscopy at the same encounter is not billed, and fluoroscopy is part of every endoscopy. Moderate sedation by the endoscopist (99151 to 99153) is generally separately reportable.8
- UnitedHealthcare commercialMember cost sharing is waived for colonoscopy at ages 45 to 75 with a network provider when billed with the policy's coding. G0105 and G0121 need no diagnosis code, while 45378, 45380, 45381, 45384, 45385 and 45388 are preventive only with a listed screening or family history diagnosis (Z12.11, Z12.12, Z80.0, the Z83.71 family and others) or when billed with G0104, G0105, G0121, G0328 or S0285. A colonoscopy after a positive stool-based or direct visualization screening test is preventive in that age band. Once a polyp has been removed, later colonoscopies are surveillance with cost sharing. Diagnostic, surveillance and therapeutic colonoscopies may need advance notification and a site-of-service review, CT colonography needs prior authorization, stool DNA testing is limited to once every 3 years, and modifier 33 is not used in the benefit decision.9
Authorizations
Medicare does not require prior authorization for endoscopy. Its gate is the frequency edit in the Common Working File, which rejects a screening billed too soon unless modifier KX marks it as the follow-on to a positive stool test, together with the age and risk rules that decide which screening code applies. Commercial plans add gates of their own: a site-of-service review when a colonoscopy is booked in a hospital outpatient department rather than a surgery center or office, advance notification for diagnostic, surveillance and therapeutic colonoscopies under some plans, and prior authorization for CT colonography. Biologic infusions for inflammatory bowel disease usually carry a drug authorization with units and an interval. Your biller pulls the last screening date and the plan's preventive coding at eligibility, confirms the site and any authorization before the procedure, and sets the modifiers from the scenario in the chart rather than from habit.
Documentation traps
- The indication written as "screening" for a patient with prior adenomatous polyps, which is high-risk screening to Medicare and surveillance with cost sharing to a commercial plan, two different claims from one word
- The positive stool test result and its date missing from the colonoscopy note, so the KX modifier and the frequency bypass cannot be defended
- Polyps not documented one by one with site and technique, so a biopsy of one and snare removal of another cannot carry modifier 59 or XS
- The reason the examination was stopped not recorded, which the modifier 53 payment and the later complete colonoscopy both depend on
- Family history recorded as "colon cancer in the family" without saying parent, sibling or child, which is what Medicare's high-risk definition for the 24 month interval requires
- Sedation documented without who gave it, so the sedation line cannot be matched to the endoscopist or the anesthesia professional and the modifier 33 or PT treatment cannot be set
What a specialist checks
Specialist or generalist for gastroenterology billing?
A generalist biller can enter a gastroenterology claim. Whether it pays turns on three things specific to gastroenterology billing, and a specialty-aware biller checks each one.
Code families
Each family billed with what the chart has to show for it.
- 43235-43259
- 45330-45350, G0104
- 45378-45398
Modifiers
Applied only where the note supports them, line by line.
- PT
- KX
- 33
If you are moving from another billing company or an in-house biller, switching billing companies follows a plan: the old and new processes run side by side until the new one is proven, and every login and every gastroenterology claim stays in your name.
What we handle
What we handle for gastroenterology practices
- Eligibility verificationCoverage and benefits checked before visits
- Medical codingCPT, ICD-10 and modifiers assigned correctly
- Claim submissionScrubbed, submitted and tracked to acceptance
- Payment postingERAs and EOBs posted, variances flagged
- Denial managementEvery denial read, worked and appealed
- Patient billing supportStatements, questions and payment plans handled
A dedicated biller with named cover, working inside your system and reporting to you on one written page. How it works sets out the five stages.
Software
Systems gastroenterology practices usually run
Your biller works inside your system as a user you create. All the systems we work in.
Questions
Questions about gastroenterology billing
How often does Medicare cover a screening colonoscopy?
Every 24 months for a patient at high risk, otherwise every 120 months, or 48 months after a screening flexible sigmoidoscopy. There is no minimum age for the colonoscopy itself. A screening colonoscopy that follows a positive stool-based test is exempt from the frequency limit when billed with modifier KX.
What happens to the claim when a screening colonoscopy finds a polyp?
The G code comes off and the diagnostic or therapeutic colonoscopy code goes on with modifier PT. Medicare waives the deductible and reduces coinsurance to 15 percent for dates of service through 2026, 10 percent in 2027 through 2029, and nothing from 2030. The patient statement has to match that, or the first call you get is about a bill for a screening the patient was told would cost nothing.
Is the colonoscopy after a positive stool DNA or FIT test a screening?
For Medicare, yes, since January 1, 2023: it is billed as a screening colonoscopy with modifier KX, the frequency limit does not apply and there is no deductible or coinsurance. The same applies after a positive blood-based biomarker test. UnitedHealthcare's commercial policy treats the follow-up colonoscopy as preventive for members aged 45 to 75 when coded to its list.
Why did a commercial plan charge the patient for a colonoscopy we billed as screening?
Usually one of five reasons: the patient is outside the plan's age band, the provider is out of network, the patient had a polyp removed before so the plan counts this one as surveillance, the CPT code was billed without a diagnosis code on the plan's preventive list, or the interval is shorter than the plan allows. Modifier 33 alone does not fix it; UnitedHealthcare, for one, does not use it in the benefit decision.
Can we bill a biopsy and a polypectomy at the same colonoscopy?
Yes, when they are on different lesions: 45380 for the biopsy and 45385 for the snare removal, with modifier 59 or XS on the biopsy. Biopsy and removal of the same polyp is one code. Control of bleeding caused by the removal is included. Several polyps removed by the same technique are one unit of one code.
How do we bill an incomplete colonoscopy?
With modifier 53 on the professional claim. Medicare pays it at a rate built from half the inputs and does not count it against the screening frequency, so the completed colonoscopy that follows is paid in full. The surgery center bills its facility fee with modifier 73 or 74. The note has to say why the examination stopped.
Do you handle infusion billing for our IBD patients?
Yes. The drug's authorization, units and interval are tracked per patient, the administration codes are billed by time with the drug on the same claim, and the plan's step therapy or preferred product rules are checked before the first dose rather than after the first denial.
What do you need from a gastroenterology practice to start?
A signed BAA, a user for your biller in your EHR, practice management system, endoscopy report writer and clearinghouse, your payer contracts, the surgery centers and hospitals where you scope, your infusion drug list, and your current screening interval tracking. Bring an aging report and a denial report to the review if you have them.
Next step
See where your gastroenterology claims are getting stuck.
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