2026 Gastroenterology Reimbursement and Coding Update (Virtual) | November 2025-Best Practices in Coding for Ancillary Services: Anesthesia, Pathology, Infusions and Diagnostic Studies

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This presentation by Kathleen Mueller from AskMueller Consulting covers best practices and documentation requirements for coding ancillary services in anesthesia, pathology, infusions, and diagnostic studies.

For <strong>anesthesia services</strong>, essential documentation includes a clear diagnosis supporting medical necessity (excluding vague terms like "rule out"), comorbidities prioritized per payer guidelines, ASA physical status class, anesthesia type, patient positioning, and precise start/stop times reflecting the anesthesia care period. Anesthesia billing is time-based in 15-minute units and uses specific CPT codes for GI endoscopic procedures with defined base units and appropriate modifiers (QZ, QS, P). Medicare policies require careful application of modifiers for sedation services, notably G0500 for moderate sedation during GI endoscopy instead of older CPT codes like 99152, with waivers on deductibles under certain conditions.

Regarding <strong>pathology services</strong>, reports must include facility info, patient identifiers, specimen dates, ordering/referring providers, clinical history, specimen location, and diagnostic sections, including microscopic and gross descriptions. Special stains and immunohistochemical (IHC) stains require documented medical necessity per Medicare LCDs to justify their use beyond routine H&E staining. Coding guidelines clarify reporting units, appropriate use of add-on codes, and emphasize that diagnosis codes must align with specimens.

For <strong>diagnostic studies</strong>, proper documentation includes facility and patient info, indication, findings, interpretation, and signatures. Billing dates depend on whether the claim covers the global service, technical component, or interpretation only, following CMS and payer-specific rules. Specific gastroenterology studies like esophageal manometry, pH studies, elastography, wireless capsule endoscopy, and others are discussed with bundling policies clarifying when procedures are separately billable or not.

In <strong>infusion services</strong>, supervision levels range from general to personal, with clear roles defined for ordering, supervising providers, and clinical staff. Documentation requirements cover medication details (including NDCs, dosage, discarded amounts), administration times, site, route, and signatures. Coding tips include modifier usage for discarded drugs (JW) or none (JZ) and emphasize billing only for administration time over 15 minutes as infusion versus injection. Infusions must occur in office settings with provider presence; billing rules for multiple infusions and medication administration methods are outlined. A list of common biologic and iron infusion agents with corresponding HCPCS codes is provided.

Throughout, compliance with payer policies, clear, complete, and legible documentation, and proper coding with attention to modifiers and medical necessity are emphasized to ensure appropriate reimbursement and audit readiness.

Asset Subtitle

Kathleen A. Mueller, RN, CPC, QMC, QGMC, CCS-P, ICD-10 Proficient

Keywords

anesthesia services

pathology services

diagnostic studies

infusion services

medical necessity documentation

CPT codes

Medicare policies

modifier usage

billing guidelines

coding best practices