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    v1.0.28
    OpenPayerBilling CodesGastroesophageal Reflux Test StudiesCPT cpt-91038-ambulatory-impedance-pH-reflux-monitoring
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    CPT 91038: Ambulatory Esophageal Impedance-pH Monitoring, 1–24 Hours

    Medicare pays $311 on average nationally for this procedure.

    CPT code 91038 describes an ambulatory gastroesophageal reflux monitoring service using a nasal catheter with intraluminal impedance electrode placement for more than 1 hour and up to 24 hours; a computer records the physiologic data and the provider interprets the results and prepares a written report. The service type is ambulatory esophageal impedance-pH monitoring and the typical site of service is an outpatient or clinic setting where the catheter is placed and continuous intraluminal impedance and pH data are collected over the monitored period.

    For related coverage guidance, see recent payer policy updates: Esophagogastroduodenoscopy (EGD) Coverage Policy, Magnetic Sphincter Augmentation for the Treatment of Gastroesophageal Reflux Disease (GERD), Fecal Analysis in the Diagnosis of Intestinal Dysbiosis and Fecal Microbiota Transplant Testing.

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    Clinical & Coding Specifications

    Clinical Context

    A typical patient is an adult referred by a gastroenterologist for ambulatory gastroesophageal reflux monitoring because of persistent heartburn, regurgitation, chest pain, or inadequate response to proton pump inhibitor therapy. The procedure uses a transnasal intraluminal impedance-pH catheter placed in the distal esophagus and connected to a data recorder for more than 1 hour and up to 24 hours. The workflow includes pre-procedure assessment (indication review, medication instructions, nasal/anatomic assessment), transnasal catheter insertion with position confirmation, patient education on symptom/event diaries and activity restrictions, ambulatory recording in the outpatient setting or an ambulatory surgery center, return for device removal (if applicable), and provider interpretation and preparation of a written report documenting reflux events, impedance findings, acid exposure times, symptom-reflux correlation, and clinical impression.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    43235Upper gastrointestinal endoscopy including esophagus, stomach, and either the duodenum; diagnostic, flexible, transoralOften performed before reflux monitoring to evaluate mucosal disease, obtain biopsies, or rule out anatomical causes interfering with catheter placement.
    91034Gastroesophageal reflux test, catheter placement and recording for up to 48 hours; placement, recording, and interpretation (note: alternate duration coding)Related ambulatory reflux testing code for different monitoring durations; used when longer monitoring is indicated or coding conventions differ.
    96372Therapeutic, prophylactic, or diagnostic injections (specify substance) (example code for clinic procedures)May be performed in clinic visits for adjunctive symptom management or for anesthesia during difficult catheter placement (rarely used).
    99213Office or other outpatient visit for the evaluation and management of an established patient, low to moderate complexityTypical encounter code used for pre-procedure evaluation or post-procedure result discussion.
    90960Dialysis procedure with single evaluation by a physician (example of physiologic monitoring category)Not directly related but listed as analogous physiologic monitoring services in coding crosswalks; included for clinical workflow comparison.

    Related Modifiers

    10 rows

    ModifierDescriptionWhen to Use
    26Modifier 26 (Professional Component) identifies and bills only the professional portion of a split service — the physician’s interpretation, report, and medical judgment — when the technical…- Use CPT Modifier -26 when you are billing only the professional component (PC) of a split‑bill eligible service—i.e., you performed the physician interpretation, medical judgment and prepared a…
    52Modifier ‑52 (Reduced Services) indicates that a service or procedure was partially reduced or omitted at the provider’s discretion, allowing reporting of the basic procedure number with a qualifier…- Use modifier -52 when a physician or qualified health professional electively reduces or omits part of a procedure or service (for example, performing fewer required views or omitting a portion of…
    53Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s…- Use modifier -53 when a physician/qualified healthcare professional has started a surgical or diagnostic procedure (e.g., anesthesia administered, incision or scope insertion) and then discontinues…
    59Modifier 59 indicates a distinct procedural service when two procedures that are not normally billed together are clinically and procedurally separate. The CPT definition (as reiterated by CMS)…- Use modifier -59 to report a distinct procedural service when documentation supports that the procedure reported is not normally billed together with another service on the same day because of a…
    76Modifier -76, Repeat Procedure or Service by Same Physician or Other Qualified Health Care Professional, is appended when the same provider performs an identical, medically necessary procedure or…- Use modifier -76 when the same physician or other qualified health care professional performs an identical procedure or service a second (or subsequent) time on the same date of service and the…
    77Modifier 77 indicates that a previously performed procedure or service was legitimately repeated by a different physician or other qualified health care professional. The AMA’s CPT definition…- Use modifier 77 when a basic procedure or service already performed is repeated by a different physician or other qualified health care professional (for example, a second provider independently…
    78CPT modifier -78 indicates an unplanned, related return to the operating or procedure room by the same provider during the global postoperative period. It is appended when treatment for a…- Use modifier -78 when an unplanned, related complication during the original procedure’s global postoperative period requires the patient to return to a formal operating or procedure room and the…
    79Modifier 79 indicates a surgical procedure performed during the postoperative global period of a prior surgery that is unrelated to the original procedure. Per AMA/CPT and CMS guidance, it is…- Use modifier 79 when the same physician (or same‑specialty physician in the same group) performs a surgical procedure during the postoperative global period of a prior surgery and the new procedure…
    91Modifier 91 — “Repeat Clinical Diagnostic Laboratory Test” — is appended when the exact same CPT laboratory test is performed more than once for the same patient on the same day because serial,…- Use modifier 91 when the exact same CPT laboratory test is performed more than once on the same patient on the same date because serial or repeated testing is medically necessary to monitor…
    99Modifier 99 is a placeholder modifier used when more modifiers apply to a single procedure than the claim form or electronic field allows. The AMA classifies it under Provider Services and Ambulatory…- Use CPT modifier -99 when more modifiers apply to a single procedure line than the claim form or payer field allows (CMS/Noridian: when more than four modifiers are needed); append modifier 99 on…

    Related Provider Taxonomies

    8 rows

    Taxonomy CodeSpecialtyNotes
    207RC0000XCardiovascular Disease PhysicianAn internist who specializes in diseases of the heart and blood vessels and manages complex cardiac conditions such as heart attacks and life-threaten…
    208000000XPediatrics PhysicianA pediatrician is concerned with the physical, emotional and social health of children from birth to young adulthood. Care encompasses a broad spectru…
    207K00000XAllergy & Immunology PhysicianAn allergist-immunologist is trained in evaluation, physical and laboratory diagnosis, and management of disorders involving the immune system. Select…
    208800000XUrology PhysicianA urologist manages benign and malignant medical and surgical disorders of the genitourinary system and the adrenal gland. This specialist has compreh…
    207ZP0105XClinical Pathology/Laboratory Medicine PhysicianA pathologist deals with the causes and nature of disease and contributes to diagnosis, prognosis and treatment through knowledge gained by the labora…
    2081H0002XHospice and Palliative Medicine (Physical Medicine & Rehabilitation) PhysicianA physical medicine and rehabilitation physician with special knowledge and skills to prevent and relieve the suffering experienced by patients with l…
    1710I1002XIndependent Duty CorpsmanA Navy Independent Duty Corpsman (IDC) is an active duty Sailor who has successfully completed one of the Navy's specific IDC training programs. IDCs…
    111NN0400XNeurology ChiropractorChiropractic Neurology is defined as the field of functional neurology that engages the internal - and external environment of the individual in a str…

    Related ICD-10-CM Codes

    26 rows

    ICD-10-CM CodeDescription
    E03.9Hypothyroidism, unspecified
    E11.9Type 2 diabetes mellitus without complications
    E66.9Obesity, unspecified
    F17.210Nicotine dependence, cigarettes, uncomplicated
    F45.41Pain disorder exclusively related to psychological factors
    G47.33Obstructive sleep apnea (adult) (pediatric)
    I10Essential (primary) hypertension
    K21.9Gastro-esophageal reflux disease without esophagitis
    K25.9Gastric ulcer, unspecified as acute or chronic, without hemorrhage or perforation
    K29.70Gastritis, unspecified, without bleeding

    Showing 1–10 of 26

    Related Payer Policy Updates

    Specialty: Gastroenterology1 / 3

    7 rows

    PolicyPayerEffective Date
    Esophagogastroduodenoscopy (EGD) Coverage Policyevicore2026-11-05
    Magnetic Sphincter Augmentation for the Treatment of Gastroesophageal Reflux Disease (GERD)univerahealthcare2026-10-15
    Fecal Analysis in the Diagnosis of Intestinal Dysbiosis and Fecal Microbiota Transplant TestingOscar Health2026-10-01
    Serum Testing for Hepatic Fibrosis in the Evaluation and Monitoring of Chronic Liver DiseaseOscar Health2026-10-01
    Pancreatic Enzyme Testing for Acute PancreatitisOscar Health2026-10-01
    Helicobacter pylori TestingOscar Health2026-10-01
    Celiac Disease TestingOscar Health2026-10-01

    Related Codes

    CPT-91030-BERNSTEIN-TEST-ACID-PROVOCATION

    CPT 91030: Bernstein Test for Heartburn Diagnosis

    CPT-91034-GASTROESOPHAGEAL-PH-MONITORING-PH-PROBE-PLACEMENT

    CPT 91034: Esophageal pH Monitoring with Interpretation and Report

    CPT-91035-TELEMETRY-PH-ESOPHAGEAL-REFLUX-TESTING

    CPT 91035: Telemetry pH Monitoring for Gastroesophageal Reflux

    CPT-91037-GASTROESOPHAGEAL-REFLUX-MONITORING-NASAL-IMPEDANCE

    CPT 91037: Gastroesophageal Reflux Test with Intraluminal Impedance

    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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