CPT 91038: Ambulatory Impedance-pH Gastroesophageal Reflux Monitoring

CPT code 91038 defines ambulatory gastroesophageal reflux monitoring using a nasal catheter with an intraluminal impedance electrode for periods greater than one hour and up to 24 hours, with computerized data recording and physician interpretation with a written report. This test is an important diagnostic tool for evaluating suspected gastroesophageal reflux disease (GERD), atypical reflux symptoms, and for correlating symptoms with reflux events when endoscopy and empiric therapy are inconclusive. Nationally, the code matters because it standardizes reporting for multichannel intraluminal impedance-pH monitoring, a procedure that influences clinical decision-making for medical, endoscopic, and surgical management of reflux.

Key payers in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of what CPT code 91038 covers, typical sites of service, and the clinical context for use. The publication summarizes payer coverage patterns, common billing considerations, and benchmarks for utilization and reimbursement where available. It also provides clarity on documentation elements tied to interpretation and written reporting. Data not available in the input is noted where applicable.

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Billing Code Overview

CPT code 91038 describes a gastroesophageal reflux test that uses a nasal catheter with an intraluminal impedance electrode to detect acid backflow from the stomach into the esophagus. The catheter is placed nasally and remains in situ for more than 1 hour and up to 24 hours, while a computer records impedance and pH data for later interpretation and reporting by the provider.

Service Type: Diagnostic ambulatory reflux monitoring with impedance and pH recording, including interpretation and written report.

Typical Site of Service: Outpatient clinic or ambulatory procedure center where long‑term nasal catheter monitoring and data recording can be performed safely and comfortably for the patient.

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CPT 91038: Ambulatory Impedance-pH Gastroesophageal Reflux Monitoring

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Billing Code Overview

Service Type: Diagnostic ambulatory reflux monitoring with impedance and pH recording, including interpretation and written report.

Typical Site of Service: Outpatient clinic or ambulatory procedure center where long‑term nasal catheter monitoring and data recording can be performed safely and comfortably for the patient.

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 Diagnoses

ICD-10 Code	Description	Clinical Relevance
`R12`	Heartburn	Common presenting symptom prompting reflux monitoring when persistent or atypical.
`K21.9`	Gastro-esophageal reflux disease without esophagitis	Primary indication for ambulatory pH-impedance testing to quantify reflux burden and symptom correlation.
`K21.0`	Gastro-esophageal reflux disease with esophagitis	Used when endoscopic or clinical evidence of esophagitis exists; monitoring can assess ongoing acid exposure.
`R07.9`	Chest pain, unspecified	Atypical chest pain may require reflux testing when cardiac causes are excluded.
`R05`	Cough	Chronic cough suspected to be related to reflux often leads to impedance-pH monitoring to assess correlation.
`R06.2`	Wheezing	Respiratory symptoms potentially related to reflux can be evaluated with this test.
`K29.70`	Gastritis, unspecified, without bleeding	Upper GI symptoms overlapping with reflux may prompt evaluation including reflux monitoring.
`R09.89`	Other specified symptoms and signs involving the circulatory and respiratory systems	Miscellaneous atypical symptoms potentially related to reflux considered for testing.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`43235`	Upper gastrointestinal endoscopy including esophagus, stomach, and either the duodenum; diagnostic, flexible, transoral	Often performed before reflux monitoring to evaluate mucosal disease, obtain biopsies, or rule out anatomical causes interfering with catheter placement.
`91034`	Gastroesophageal 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.
`96372`	Therapeutic, 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).
`99213`	Office or other outpatient visit for the evaluation and management of an established patient, low to moderate complexity	Typical encounter code used for pre-procedure evaluation or post-procedure result discussion.
`90960`	Dialysis 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

Modifier	Description	When to Use
26	Modifier 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…
52	Modifier ‑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…
53	Modifier 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…
59	Modifier 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…
76	Modifier -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…
77	Modifier 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…
78	CPT 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…
79	Modifier 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…
91	Modifier 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…
99	Modifier 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 Code	Specialty	Notes
207RC0000X	Cardiovascular Disease Physician	An internist who specializes in diseases of the heart and blood vessels and manages complex cardiac conditions such as heart attacks and life-threaten…
208000000X	Pediatrics Physician	A pediatrician is concerned with the physical, emotional and social health of children from birth to young adulthood. Care encompasses a broad spectru…
207K00000X	Allergy & Immunology Physician	An allergist-immunologist is trained in evaluation, physical and laboratory diagnosis, and management of disorders involving the immune system. Select…
208800000X	Urology Physician	A urologist manages benign and malignant medical and surgical disorders of the genitourinary system and the adrenal gland. This specialist has compreh…
207ZP0105X	Clinical Pathology/Laboratory Medicine Physician	A pathologist deals with the causes and nature of disease and contributes to diagnosis, prognosis and treatment through knowledge gained by the labora…
2081H0002X	Hospice and Palliative Medicine (Physical Medicine & Rehabilitation) Physician	A physical medicine and rehabilitation physician with special knowledge and skills to prevent and relieve the suffering experienced by patients with l…
1710I1002X	Independent Duty Corpsman	A Navy Independent Duty Corpsman (IDC) is an active duty Sailor who has successfully completed one of the Navy's specific IDC training programs. IDCs…
111NN0400X	Neurology Chiropractor	Chiropractic Neurology is defined as the field of functional neurology that engages the internal - and external environment of the individual in a str…

CPT 91030: Bernstein Test for Acid-Induced Heartburn

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

CPT 91034: Gastroesophageal Reflux pH Monitoring with Electrode Placement

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 Monitoring with Transnasal Impedance

References

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.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.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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Clinical & Coding Specifications

Clinical Context

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`R12`	Heartburn	Common presenting symptom prompting reflux monitoring when persistent or atypical.
`K21.9`	Gastro-esophageal reflux disease without esophagitis	Primary indication for ambulatory pH-impedance testing to quantify reflux burden and symptom correlation.
`K21.0`	Gastro-esophageal reflux disease with esophagitis	Used when endoscopic or clinical evidence of esophagitis exists; monitoring can assess ongoing acid exposure.
`R07.9`	Chest pain, unspecified	Atypical chest pain may require reflux testing when cardiac causes are excluded.
`R05`	Cough	Chronic cough suspected to be related to reflux often leads to impedance-pH monitoring to assess correlation.
`R06.2`	Wheezing	Respiratory symptoms potentially related to reflux can be evaluated with this test.
`K29.70`	Gastritis, unspecified, without bleeding	Upper GI symptoms overlapping with reflux may prompt evaluation including reflux monitoring.
`R09.89`	Other specified symptoms and signs involving the circulatory and respiratory systems	Miscellaneous atypical symptoms potentially related to reflux considered for testing.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`43235`	Upper gastrointestinal endoscopy including esophagus, stomach, and either the duodenum; diagnostic, flexible, transoral	Often performed before reflux monitoring to evaluate mucosal disease, obtain biopsies, or rule out anatomical causes interfering with catheter placement.
`91034`	Gastroesophageal 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.
`96372`	Therapeutic, 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).
`99213`	Office or other outpatient visit for the evaluation and management of an established patient, low to moderate complexity	Typical encounter code used for pre-procedure evaluation or post-procedure result discussion.
`90960`	Dialysis 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

Modifier	Description	When to Use
26	Modifier 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…
52	Modifier ‑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…
53	Modifier 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…
59	Modifier 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…
76	Modifier -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…
77	Modifier 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…
78	CPT 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…
79	Modifier 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…
91	Modifier 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…
99	Modifier 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 Code	Specialty	Notes
207RC0000X	Cardiovascular Disease Physician	An internist who specializes in diseases of the heart and blood vessels and manages complex cardiac conditions such as heart attacks and life-threaten…
208000000X	Pediatrics Physician	A pediatrician is concerned with the physical, emotional and social health of children from birth to young adulthood. Care encompasses a broad spectru…
207K00000X	Allergy & Immunology Physician	An allergist-immunologist is trained in evaluation, physical and laboratory diagnosis, and management of disorders involving the immune system. Select…
208800000X	Urology Physician	A urologist manages benign and malignant medical and surgical disorders of the genitourinary system and the adrenal gland. This specialist has compreh…
207ZP0105X	Clinical Pathology/Laboratory Medicine Physician	A pathologist deals with the causes and nature of disease and contributes to diagnosis, prognosis and treatment through knowledge gained by the labora…
2081H0002X	Hospice and Palliative Medicine (Physical Medicine & Rehabilitation) Physician	A physical medicine and rehabilitation physician with special knowledge and skills to prevent and relieve the suffering experienced by patients with l…
1710I1002X	Independent Duty Corpsman	A Navy Independent Duty Corpsman (IDC) is an active duty Sailor who has successfully completed one of the Navy's specific IDC training programs. IDCs…
111NN0400X	Neurology Chiropractor	Chiropractic Neurology is defined as the field of functional neurology that engages the internal - and external environment of the individual in a str…

CPT 91030: Bernstein Test for Acid-Induced Heartburn

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

CPT 91034: Gastroesophageal Reflux pH Monitoring with Electrode Placement

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 Monitoring with Transnasal Impedance

References

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.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.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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CPT 91038: Ambulatory Impedance-pH Gastroesophageal Reflux Monitoring

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Billing Code Overview

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CPT 91038: Ambulatory Impedance-pH Gastroesophageal Reflux Monitoring

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Billing Code Overview

Clinical & Coding Specifications

Clinical Context

Related Diagnoses

Related CPT Codes

Related Modifiers

Related Provider Taxonomies

Related Codes

References

Clinical & Coding Specifications

Clinical Context

Related Diagnoses

Related CPT Codes

Related Modifiers

Related Provider Taxonomies

Related Codes

References