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Reflux Testing · Katy & Cypress
Esophageal pH Monitoring for Reflux Testing
Esophageal pH monitoring is a test that measures how often and for how long stomach acid backs up into the esophagus, usually over 24 to 96 hours. It helps confirm whether heartburn, regurgitation, chest discomfort or a chronic cough is caused by acid reflux, especially when reflux medicine has not helped or an upper endoscopy looked normal. At United Gastroenterology Associates, PLLC, Muhammad Ali Khan, MD, FACP, FASGE, orders and interprets reflux testing for patients from Katy, Cypress and Greater Houston.
Reflux evaluation with Dr. Muhammad Ali Khan
Meet Your Reflux Testing Specialist: Muhammad Ali Khan, MD, FACP, FASGE
BOARD-CERTIFIED Gastroenterologist and Hepatologist
CREDENTIALS AT A GLANCE
Board-Certified
Gastroenterology, hepatology, and internal medicine
Academic Medicine
Former Associate Professor, UT MD Anderson Cancer Center
Published Research
More than 100 peer-reviewed articles in gastroenterology
FACP and FASGE
Fellow, American College of Physicians and American Society for Gastrointestinal Endoscopy
“My gastroenterology & hepatology practice is dedicated to working closely with you to develop a personalized treatment plan that meets your unique needs and preferences.”
Dr. Muhammad Ali Khan, MD, FACP, FASGE
Board-certified gastroenterologist and hepatologist, United Gastroenterology Associates
Reflux testing at United Gastroenterology Associates is ordered and interpreted by Dr. Khan, a gastroenterologist board-certified in gastroenterology, hepatology and internal medicine and a Fellow of the American Society for Gastrointestinal Endoscopy. He uses pH results alongside your symptoms and endoscopy findings to decide on the next step.
Dr. Khan is a former Associate Professor at The University of Texas MD Anderson Cancer Center and has authored more than 100 peer-reviewed publications.
Related areas of care
- Heartburn and GERD
- Chronic cough or hoarseness linked to reflux
- Upper endoscopy (EGD)
- Difficulty swallowing
- Gastritis and stomach pain
What Is Esophageal pH Monitoring?
Esophageal pH monitoring, also called ambulatory reflux monitoring, uses a small sensor in the esophagus to record acid levels while you go about a normal day. Each time acid from the stomach reaches the sensor, the reading drops, which shows how often reflux happens and how long the acid stays.
The test is a diagnostic step, not a treatment. It answers a specific question: are your symptoms really caused by acid reflux? The answer helps decide whether to continue, change or stop reflux medicine, whether to look for another cause, and whether a procedure for reflux makes sense. Treatment options are covered on our GERD care page.
Testing is usually considered after an evaluation and, in many cases, an upper endoscopy. Dr. Khan decides whether pH monitoring is needed and which type of test fits your history.
pH monitoring at a glance
- Measures: acid reflux into the esophagus
- Types: 24-hour catheter test or wireless capsule test (48 to 96 hours)
- During the test: normal meals and activities, with a symptom diary
- Medicines: acid reducers are often paused beforehand, only as instructed
- Results: reviewed by your gastroenterologist at a follow-up visit
Your preparation instructions come from the office and may differ.
Board-Certified Gastroenterologist
Gastroenterology, hepatology and internal medicine
Results Interpreted by a Specialist
Acid exposure and symptom patterns reviewed by Dr. Khan
Testing With Endoscopy Available
Upper endoscopy and reflux testing in one practice
Two Locations
Offices in Katy and Cypress
Who May Need Reflux Testing?
Many people with typical heartburn are treated without testing. pH monitoring becomes useful when the diagnosis is uncertain, when treatment is not working as expected, or before a decision that depends on proof of reflux, such as anti-reflux surgery or an endoscopic reflux procedure.
It is also used when symptoms are less typical, such as a chronic cough, hoarseness or chest discomfort, to find out whether reflux plays a role. Testing can prevent years of medicine for a problem that may not be reflux at all.
Chest pain can come from the heart.
Call 911 for chest pain with shortness of breath, sweating, nausea or pain spreading to the arm, neck or jaw. Heart causes should be ruled out before chest pain is blamed on reflux.
Common reasons for pH monitoring
- Heartburn or regurgitation that continues despite reflux medicine
- Reflux symptoms with a normal upper endoscopy
- Chest discomfort after heart causes have been ruled out
- Chronic cough, hoarseness or throat clearing that may be linked to reflux
- Planning for anti-reflux surgery or an endoscopic reflux procedure
- Deciding whether long-term acid-reducing medicine is needed
A symptom alone does not confirm a diagnosis. Symptoms should be evaluated by a qualified medical professional.
Catheter pH Test vs. Wireless Capsule Test
There are two main ways to measure acid in the esophagus. Both record your acid levels during a normal routine, but they differ in how the sensor is placed and how long the recording lasts.
| Feature | 24-hour catheter test | Wireless capsule test |
|---|---|---|
| How the sensor is placed | A thin, flexible tube is passed through the nose into the esophagus while you are awake | A small capsule is attached to the esophageal lining during an upper endoscopy |
| Recording time | About 24 hours | Usually 48 to 96 hours |
| What you wear | A small recorder connected to the tube | A small receiver kept on your belt or nearby |
| Daily routine | Normal meals and activities; the tube is visible at the nose | Normal meals and activities; nothing passes through the nose |
| When it ends | The tube is removed after the recording | The capsule detaches on its own within days and passes in the stool |
| Non-acid reflux | Can be measured when combined with impedance (pH-impedance) | Measures acid only |
| Special precautions | None beyond the test instructions | Avoid MRI for 30 days after the capsule is placed |
Which test is right for you depends on your symptoms, your earlier test results and whether you are being tested on or off acid-reducing medicine. Dr. Khan will explain the option he recommends and why.
Still Having Reflux Symptoms on Medicine?
Dr. Khan can review your symptoms and earlier tests and explain whether reflux testing would help clarify the cause. New patients are welcome in Katy and Cypress.
What Happens During Esophageal Acid Monitoring?
Always follow the instructions provided by the office. This is the usual sequence.
Prepare as instructed
You may be asked to stop proton pump inhibitors about seven days before the test and other acid reducers for a shorter time, and to avoid eating for a few hours before the sensor is placed. Do not change a prescription unless told to.
Sensor placement
For a catheter test, a thin tube is passed through the nose. For a wireless test, the capsule is attached during an upper endoscopy with sedation.
A normal day
Eat your usual foods and follow your routine. Record meals, symptoms and when you lie down, and press the button on the recorder when symptoms occur.
Ending the test
The catheter is removed after about 24 hours, or you return the wireless receiver when the recording is complete. The capsule passes on its own.
Your results
Dr. Khan reviews how much time acid spent in the esophagus and whether your symptoms matched reflux episodes, then discusses next steps.
Understanding Your pH Monitoring Results
The main measurement is acid exposure time: the percentage of the recording during which the esophagus was exposed to acid. Under the Lyon Consensus 2.0 criteria used by reflux specialists, acid exposure below 4% of the time is generally considered normal, above 6% supports a diagnosis of GERD, and values in between are considered inconclusive and are interpreted alongside other findings.
The report also shows how many reflux episodes occurred and whether your symptoms happened at the same times, which helps judge whether reflux is causing what you feel.
Can pH monitoring diagnose GERD when an endoscopy is normal?
Yes. Many people with reflux have no visible damage on endoscopy. pH monitoring measures the acid itself, so it can confirm GERD in these cases or show that acid reflux is unlikely to be the cause.
What happens after the test?
If reflux is confirmed, Dr. Khan will discuss treatment options, which may include lifestyle changes, medicine or, for selected patients, a procedure. If reflux is not the cause, the evaluation turns to other conditions, such as functional heartburn, eosinophilic esophagitis or an esophageal motility problem.
Is pH Monitoring Safe?
Esophageal pH monitoring is a low-risk test. A catheter can cause a runny nose, throat irritation or, rarely, a nosebleed. A wireless capsule can cause a mild feeling of something in the chest, and occasionally it detaches early or, rarely, needs to be removed. Because the capsule is placed during an endoscopy, the usual sedation precautions apply, including an adult driver.
If you have a wireless capsule, avoid MRI scans for 30 days after placement and tell other doctors about the test.
Insurance and Self-Pay Options
United Gastroenterology Associates participates with many major insurance plans. Coverage and benefits depend on your specific plan and must be verified, and some plans require prior authorization for diagnostic testing. Please contact the office or your insurance carrier to verify benefits for your specific plan and service.
Esophageal pH Monitoring FAQs
Answers to common questions about reflux testing at United Gastroenterology Associates.
What test can confirm that symptoms are caused by acid reflux?
Esophageal pH monitoring, also called ambulatory reflux monitoring, is the main test for confirming acid reflux. It records how often and how long acid enters the esophagus over 24 to 96 hours and whether your symptoms happen at the same times. An upper endoscopy can show reflux damage, but many people with GERD have a normal endoscopy.
Where can I get 24-hour esophageal pH monitoring in Katy or Cypress?
United Gastroenterology Associates provides reflux testing for patients seen at its Katy office (23920 Katy Freeway, Suite 555) and Cypress office (21216 Northwest Freeway, Suite 640). Dr. Muhammad Ali Khan evaluates your symptoms, explains which type of pH test fits your situation and reviews the results with you. Call (346) 340-4414.
What test measures acid exposure when reflux medicine is not working?
Esophageal pH monitoring. If GERD has never been proven, the test is usually done after stopping acid-reducing medicine for about a week, to see whether reflux is really the cause. If GERD is already proven and symptoms continue on twice-daily medicine, a pH-impedance test done while taking the medicine can show whether acid or non-acid reflux is still reaching the esophagus.
Can pH monitoring diagnose GERD when an endoscopy is normal?
Yes. Many people with reflux symptoms have no visible damage on endoscopy. pH monitoring measures the acid itself, so it can confirm GERD in these cases or show that reflux is not the cause, which points the evaluation toward other conditions.
Do I need to stop my reflux medicine before the test?
Often, yes, but only as instructed. Proton pump inhibitors are commonly stopped about seven days before testing, and other acid reducers for a shorter time. Some tests are intentionally done on medicine. Follow the instructions you receive and ask the office if you are unsure.
Is esophageal pH monitoring painful?
It is not usually painful. A catheter through the nose can feel odd or cause throat irritation, and a wireless capsule may cause a mild sensation in the chest, especially when swallowing. Most people complete the test while following their normal routine.
Can I eat and work normally during the test?
Yes. The test works best when you follow your usual routine, eat your normal foods and keep a record of meals, symptoms and when you lie down, so the results reflect a typical day.
Reflux Testing Near Katy and Cypress
Dr. Khan evaluates reflux symptoms at both offices of United Gastroenterology Associates, serving patients from Katy, Cypress, Fulshear, Richmond, Rosenberg and communities throughout Greater Houston.
United Gastroenterology Associates – Katy
Katy Freeway (I-10) near the Grand Parkway
- Address: 23920 Katy Freeway, Suite 555, Katy, TX 77494
- Phone: (346) 340-4414
- Hours: Monday–Friday, 8:30 AM–5:00 PM (closed 12:00–1:30 PM for lunch; last appointment 4:30 PM)
United Gastroenterology Associates – Cypress
Northwest Freeway (US-290) in Cypress
- Address: 21216 Northwest Freeway, Suite 640, Cypress, TX 77429
- Phone: (346) 340-4414
- Hours: Monday–Friday, 8:30 AM–5:00 PM (closed 12:00–1:30 PM for lunch; last appointment 4:30 PM)
Find Out What Is Causing Your Reflux Symptoms
If heartburn, regurgitation or a chronic cough continues despite treatment, testing can bring clarity. Call (346) 340-4414 or request an appointment with Dr. Khan.
Sources
- Gyawali CP, et al.. Updates to the modern diagnosis of GERD: Lyon Consensus 2.0. Gut, 2024. gut.bmj.com
- Katz PO, et al.. ACG Clinical Guideline for the Diagnosis and Management of Gastroesophageal Reflux Disease. Am J Gastroenterol, 2022. journals.lww.com
- National Institute of Diabetes and Digestive and Kidney Diseases. Diagnosis of GER & GERD. niddk.nih.gov
This page provides general educational information and does not replace medical advice, diagnosis or treatment. Follow the testing instructions provided by your physician. For a medical emergency, call 911. Last updated October 5, 2026.