Gastroenterology Billing & Coding Guide
Screening colonoscopy 0-pay vs diagnostic conversion, modifier 33/PT, biopsy bundling.
Common Gastroenterology CPT Codes
Ranked by claim frequency, with current MPFS work RVUs and global periods.
| Code | Description | Work RVU | Total RVU | Global |
|---|---|---|---|---|
| 45378 | Diagnostic colonoscopy | 3.18 | 11.32 | 000 |
| 45380 | Colonoscopy and biopsy | 3.47 | 14.37 | 000 |
| 45381 | Colonoscopy submucous njx | 3.47 | 14.68 | 000 |
| 45384 | Colonoscopy w/lesion removal | 3.97 | 16.15 | 000 |
| 45385 | Colonoscopy w/lesion removal | 4.46 | 14.97 | 000 |
| 45388 | Colonoscopy w/ablation | 4.76 | 79.62 | 000 |
| 45390 | Colonoscopy w/resection | 5.89 | 8.69 | 000 |
| 45391 | Colonoscopy w/endoscope us | 4.52 | 6.77 | 000 |
| 45392 | Colonoscopy w/endoscopic fnb | 5.36 | 7.96 | 000 |
| 45393 | Colonoscopy w/decompression | 4.56 | 6.54 | 000 |
| 45398 | Colonoscopy w/band ligation | 4.10 | 27.02 | 000 |
| 43235 | Egd diagnostic brush wash | 2.04 | 9.66 | 000 |
| 43239 | Egd biopsy single/multiple | 2.33 | 12.54 | 000 |
| 43249 | Esoph egd dilation <30 mm | 2.60 | 35.34 | 000 |
| 43259 | Egd us exam duodenum/jejunum | 3.94 | 5.95 | 000 |
| 43236 | Uppr gi scope w/submuc inj | 2.33 | 13.36 | 000 |
| 43237 | Endoscopic us exam esoph | 3.38 | 5.18 | 000 |
| 43238 | Egd us fine needle bx/aspir | 4.06 | 6.12 | 000 |
| 43240 | Egd w/transmural drain cyst | 6.97 | 10.24 | 000 |
| 43242 | Egd us fine needle bx/aspir | 4.61 | 6.88 | 000 |
What Gastroenterology practices are leaving on the table
High-value services that consistently get under-billed across the specialty. Each one is rooted in current 2026 fee schedule and policy updates.
Screening-to-diagnostic conversion: When a polyp is found during screening, the procedure converts to diagnostic (45385-PT). The reimbursement goes from ~$260 (45378) to ~$380 (45385). Patient still has zero cost-share.
Multi-site biopsies/polypectomies: Each DIFFERENT site is separately billable. 3 polyps in 3 different segments = 45385 + 45385-59 + 45385-59. Document location of each.
EGD + colonoscopy same session: These are NOT bundled (different anatomic regions). Bill both full codes. Many practices only bill the colonoscopy and miss $200+ on the EGD.
Capsule endoscopy (91110): $350-500 per procedure. Indicated for occult GI bleeding, Crohn's monitoring, celiac follow-up. Requires prior auth but rarely denied with proper indication.
Hemorrhoid banding (46221): Can be done in-office. $150-200 per session. Often 3 sessions needed. High patient demand, low overhead.
Pathology coordination: Ensure all specimens go to a pathology group that bills separately. The GI practice can own the pathology lab for additional revenue (compliance considerations apply).
Code pairs that auto-bundle to CO-97
From the National Correct Coding Initiative for Gastroenterology. The rationale tells you when a modifier legitimately bypasses the edit and when it cannot.
Diagnostic colonoscopy (45378) bundles into colonoscopy with biopsy (45380). If biopsy is taken, bill 45380 only — NOT 45378 + 45380.
Biopsy (45380) is included in polypectomy (45385) at the SAME site. If biopsy at one site and polypectomy at another = 45380 + 45385-59.
Snare polypectomy (45385) + ablation (45388) at same site = only bill the more extensive procedure. Different sites = both with 59.
Diagnostic EGD (43235) bundles into EGD with biopsy (43239). If biopsy taken, bill 43239 only.
Colonoscopy + EGD same session: bill both (different anatomic regions). No modifier needed — they are not bundled.
Biopsy (45380) + submucosal injection (45381) at same site = 45381 only. Different sites = both with 59.
Modifier Guidance for Gastroenterology
When each modifier legitimately applies in this specialty, with denial-pattern context and audit-defense documentation.
Preventive screening — used on screening colonoscopy (45378-33). Converts patient cost-share to $0 under ACA. Critical for patient satisfaction.
Screening colonoscopy converted to diagnostic — polyp found and removed. Bill 45385-PT (not 45378-33). Patient should still have zero cost-share under ACA.
Separate anatomic site — biopsy at cecum + polypectomy at sigmoid = 45380 + 45385-59. Must document different locations in op note.
Reduced service — incomplete colonoscopy (didn't reach cecum). Bill 45378-52. Payment reduced 50%.
Discontinued procedure — stopped due to patient distress or emergency. Bill 45378-53 for work performed.
Discontinued ASC procedure — 73 before anesthesia, 74 after anesthesia. Facility billing only.
Documentation requirements
What needs to live in the encounter note for these codes to survive a payer audit.
- Colonoscopy: Document extent of exam (cecum reached? photo of appendiceal orifice), quality of prep (Boston Bowel Prep Scale), withdrawal time (6+ minutes), findings per segment, and interventions per site.
- Polypectomy: Document polyp location (specific segment), size (measured, not estimated), morphology (pedunculated/sessile/flat), removal technique (snare/forceps/EMR), retrieval for pathology, and complete removal confirmed.
- EGD: Document indication, extent of exam (to duodenum), findings per region (esophagus, GEJ, stomach, duodenum), biopsies taken (location and number), and interventions.
- Screening vs diagnostic: If the indication is screening, use Z12.11 + modifier 33 (or PT if polyp found). If symptoms prompted the exam, use the symptom ICD-10. This determines patient cost-share.
OIG and audit triggers in Gastroenterology
Patterns that show up in OIG Work Plans, RAC audits, and CERT improper payment reviews. Build internal compliance checks around these.
Diagnostic included in therapeutic: 45378 (diagnostic) is ALWAYS included in 45380/45385/etc. The biggest GI billing mistake is billing the diagnostic scope with the therapeutic scope.
Screening modifier confusion: Screening = Z12.11 + modifier 33. If polyp found = change to 45385-PT + Z12.11. Do NOT change to a diagnostic ICD-10 code — that triggers patient cost-share.
Same-site biopsy + polypectomy: If you biopsy a polyp and then remove it, that's ONE procedure (the polypectomy). You cannot bill biopsy + polypectomy at the same site.
Incomplete colonoscopy: If you can't reach the cecum, bill 45378-52 (reduced service). Do NOT bill the full code — this is audit bait. Document why incomplete (poor prep, obstruction, patient discomfort).
Surveillance interval errors: Billing colonoscopy before the recommended interval (based on prior findings) = medical necessity denial. Track each patient's recommended interval.
Anesthesia for colonoscopy: Bill 00810 for anesthesia (anesthesiologist bills). The GI physician does NOT bill for sedation if an anesthesiologist is present. If the GI provides moderate sedation, bill 99152/99153.
Payer-specific billing notes
Where the major payers diverge from generic Medicare rules in Gastroenterology.
ME Medicare +
Screening colonoscopy covered every 10 years (average risk) or 4 years (high risk). No cost-share for screening. If polyp found and removed, still no cost-share (modifier PT). Anesthesia covered for screening colonoscopy.
UN UnitedHealthcare +
Follows USPSTF guidelines for screening (age 45+). Prior auth not required for screening. Surveillance intervals must follow multi-society guidelines. Requires op note for all therapeutic procedures.
AE Aetna +
Covers screening at 45+. Requires prior auth for capsule endoscopy and advanced procedures. EGD requires documented symptoms (not screening). Denies repeat colonoscopy within 3 years without documented indication.
BC BCBS +
Coverage varies by state plan. Most cover screening at 45+. Some plans require specific screening ICD-10 codes (Z12.11). Follow-up colonoscopy coverage depends on prior findings.
CI Cigna +
Follows multi-society guidelines for intervals. Requires auth for advanced endoscopy (ERCP, EUS). Screening colonoscopy at 45+ with no cost-share.
Standard Gastroenterology coding workflow
1. Determine screening vs diagnostic (what was the INDICATION?). 2. Document all findings by anatomic segment. 3. Bill the MOST extensive procedure at each site. 4. Add modifier 59/XS for each additional site. 5. For screening with polyp: change to 45385-PT. 6. If EGD also performed, bill separately (no modifier needed). 7. Verify ICD-10 matches screening vs diagnostic determination. 8. Track surveillance interval for follow-up scheduling.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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