Screening, diagnostic, or a screening that became diagnostic
A screening colonoscopy for an average-risk patient is reported to Medicare as G0121, or G0105 for a high-risk patient, and to most commercial payers as 45378 with modifier 33. If the endoscopist finds and removes a polyp, the procedure becomes diagnostic: the code changes to 45385 for snare polypectomy or 45380 for biopsy, and the screening intent has to be preserved on the claim so the patient’s preventive benefit still applies.
For Medicare that preservation is modifier PT on the therapeutic code, which waives the deductible and marks the case as a screening. Commercial payers vary: some accept modifier 33 on the therapeutic code, some want the screening diagnosis Z12.11 sequenced first, and some want both. We maintain the rule per payer, and the coder applies it from the procedure report, not from what the schedule said.
Anesthesia and pathology have to tell the same story
A colonoscopy generates up to three claims: the endoscopist, the anesthesia provider (00812 for a screening colonoscopy, 00811 for other lower endoscopy) and the pathologist reading the polyp (88305). If the endoscopist bills a screening with PT and the anesthesia group bills 00811 with nothing to indicate a screening, the patient gets an anesthesia bill on a procedure that was supposed to cost nothing.
We share the final screening-versus-diagnostic determination with the anesthesia group and the pathology lab on the day the report is finalized. When the practice owns its ASC, the facility claim is reconciled to the professional claim before either goes out. It is unglamorous work, but it is what keeps patients trusting the screening program.
Incomplete procedures, multiple techniques and the modifiers between them
Not every colonoscopy reaches the cecum. When prep is poor or the scope cannot be advanced, the claim is reported with modifier 53, and Medicare pays the incomplete screening at a reduced amount while still allowing the repeat. Billing the full code for an incomplete procedure is an overpayment, and it makes the repeat look like a frequency violation.
Multiple techniques are the other trap. Removing one polyp by snare (45385) and biopsying a separate lesion (45380) is billable as two procedures with modifier 59 or XS on the second, but only if the report documents different lesions. Snare and biopsy of the same polyp pays once. An upper endoscopy in the same session is paid under multiple-endoscopy rules rather than denied, so a denial there is a coding problem, not a payer problem.
Infusions, biologics and the buy-and-bill exposure
Inflammatory bowel disease practices carry an infusion suite, and the drug is usually worth more than the visit. Infliximab (J1745), vedolizumab (J3380), ustekinumab and their biosimilars are billed by unit with the NDC, and the infusion itself is 96413 for the first hour and 96415 for each additional hour. The drug line denies when units are calculated wrong, when the NDC does not match the J code, when the biosimilar code is used for the reference product, or when the plan requires specialty pharmacy rather than buy-and-bill.
Prior authorization for biologics is a recurring task. Authorizations expire, dose escalations need new approvals, and a plan-mandated switch to a biosimilar has to be reflected in the code before the next infusion. We track authorization end dates and approved dose against the infusion schedule so a maintenance dose is not infused on an expired approval. When a claim does deny for authorization, we fix the calendar, not just the claim.
GI billing outside the endoscopy suite
Office visits are E/M encounters, and the common error is billing an E/M on the day of a scheduled endoscopy for the pre-procedure history and physical, which is part of the procedure. A separately payable E/M that day needs modifier 25 and a genuinely separate problem. Capsule endoscopy (91110), esophageal manometry (91010) and liver elastography (91200) each carry payer-specific coverage criteria, and several require a documented prior inconclusive standard study.
Hemorrhoid banding (46221), balloon dilation through the scope (43249) and PEG placement carry global periods or bundle with the endoscopy in the same session, so code order and modifiers decide payment. We run every multi-procedure claim through the NCCI edit pairs before submission and, where the report supports it, attach the modifier at coding rather than after the denial.
How we take on gastroenterology billing
The first step is a free A/R review of your aging report, read by procedure family: colonoscopy claims stuck on modifiers look different from infusion claims stuck on authorization, and each gets its own plan. We work inside your existing practice management and endoscopy reporting systems, the coders are credentialed through AAPC or AHIMA, and a BAA is signed before we see a single report.
Switching runs as a two-to-four-week parallel period in which both billers see the same cases and we compare coding case by case. In GI that comparison is usually where each payer’s screening-versus-diagnostic rule first gets written down. After the initial term the engagement is month-to-month, with a named account manager who knows your payer mix and your ASC arrangement.
