Gastroenterology billing is dominated by endoscopy. The 2026 CPT code set retained the colonoscopy and EGD code structures with NCCI edit refinements, and the screening-versus-diagnostic-versus-surveillance distinction continues to be the highest-impact billing decision GI practices make. The 2026 Medicare Physician Fee Schedule maintained the modifier PT structure that allows screening colonoscopies that turn diagnostic to retain the patient’s screening cost-share protections under the Affordable Care Act. For GI practices, the 2026 playbook is documentation that supports the right billing pathway from the patient’s history through the post-procedure note.
Screening, diagnostic, and surveillance: three pathways
Every colonoscopy falls into one of three pathways, and the documentation determines which. Screening colonoscopy (G0121 for average-risk Medicare; 45378 with ICD-10 Z12.11 for commercial average-risk) applies to asymptomatic patients without personal or family history that elevates risk, performed at the recommended age and interval. Diagnostic colonoscopy (45378 and the polyp-removal codes 45380-45390 with appropriate ICD-10) applies to patients with symptoms (bleeding, change in bowel habits, abdominal pain) or positive findings on prior testing. Surveillance colonoscopy (G0105 for high-risk Medicare; 45378 with personal history of polyps or family history of colorectal cancer) applies to patients with prior findings that elevate risk above average.
The PT modifier: when screening turns diagnostic
When a screening colonoscopy uncovers a polyp that requires removal, the procedure becomes diagnostic, and the appropriate diagnostic code (typically 45385 for snare polypectomy or 45380 for biopsy) is billed. Without intervention, the patient would lose the screening cost-share protection under the ACA. Modifier PT (colorectal screening test converted to diagnostic) preserves the patient’s coverage as a screening service for cost-sharing purposes while allowing the practice to bill the diagnostic code at the higher reimbursement. The modifier applies only to commercial plans subject to ACA preventive coverage; Medicare uses a parallel structure with the KX modifier or specific G-codes.
EGD coding
Esophagogastroduodenoscopy (EGD) codes (43235-43259) start at 43235 (diagnostic with brushings or washings if performed) and add specific procedural variants. Common add-on or alternative codes include 43239 (with biopsy single or multiple), 43251 (with removal of polyp by snare), 43252 (with optical endomicroscopy), 43253 (with EUS-guided fine needle aspiration). EGD bundling rules under NCCI prevent billing certain combinations together; the most common bundling failure is billing both 43235 and 43239 for the same encounter when the biopsy code (43239) already includes the diagnostic component.
Colonoscopy procedure codes
Colonoscopy codes (45378-45398) follow a similar pattern. CPT 45378 is the diagnostic colonoscopy, 45380 is colonoscopy with biopsy, 45385 is colonoscopy with snare removal of polyp, 45388 is colonoscopy with ablation of tumor or polyp, 45390 is colonoscopy with endoscopic mucosal resection. When multiple techniques are used in the same procedure, the highest-complexity code is typically the primary, with appropriate modifiers for the others. Documentation must specify the technique used for each polyp or lesion (snare versus cold forceps biopsy versus ablation), the size and location, and the disposition (sent to pathology or destroyed).
Polypectomy bundling
When multiple polyps are removed at the same colonoscopy, the procedure is billed once for the highest-complexity technique used, not once per polyp. A colonoscopy with snare removal of three polyps and cold forceps biopsy of two more polyps bills as 45385 (snare removal) once, with no separate billing for the cold forceps biopsies. The exception is when distinct techniques are used in distinctly different anatomic regions; modifier 59 or the X-modifiers may apply, but the documentation must establish the distinction. Most practices over-bill polypectomy by attempting to bill multiple codes for a single colonoscopy.
Capsule endoscopy and BRAVO pH monitoring
Capsule endoscopy (91110, 91113) and BRAVO pH monitoring (91035) are billed as discrete services with their own coverage criteria. Capsule endoscopy requires documentation of failed conventional endoscopy or specific clinical indications (occult GI bleeding, suspected small bowel disease). BRAVO pH monitoring requires documentation of specific reflux indication and prior conventional pH testing if applicable. Coverage varies by payer, and prior authorization is common. Practices that schedule these without verifying coverage in advance see denials at high rates.
ASC versus office-setting decision
Like other procedural specialties, GI faces a site-of-service decision under the 2026 PFS. The facility-payment cuts under CMS-1832-F apply to facility-based endoscopy, while non-facility (ASC) reimbursement holds steadier. Practices with credentialing and equipment to perform endoscopy in an in-network ASC capture better reimbursement than the same procedure performed in a hospital outpatient department. The decision requires payer-by-payer review, ASC contract status, and quality-of-care alignment.
How MHB helps GI practices
For GI practices that want specialty-trained coders working endoscopy claims with screening pathway discipline, polypectomy bundling, and modifier PT workflow, our team supports specialty medical coding for gastroenterology.
The bottom line
GI billing in 2026 turns on three things: choosing the right pathway between screening, diagnostic, and surveillance; applying the PT modifier when a screening converts to diagnostic; and documenting polypectomy techniques specifically enough to bill the correct single code rather than multiple bundled codes. Practices that build documentation aligned to these decisions capture full reimbursement and protect patient cost-share. Practices that improvise leak revenue and create patient billing disputes.
Authoritative sources
This article cites the following primary sources for billing-code and regulatory guidance. Always confirm current rules and codes with the publishing authority before applying to a specific claim.
