Motility and Functional Gastrointestinal Disorders Center pH Probe Study

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What is a pH probe study?

  • A pH probe study determines if acid from the stomach is coming up into the esophagus (food tube), known as gastroesophageal reflux.
  • In this test, a thin, flexible tube is passed through the nose, down the back of the throat and into the esophagus. The tube is carefully taped in place. The end of the tube is attached to a small recording machine. This recorder has a belt that may be buckled around your child's waist or carried over a shoulder.
  • A pH probe study takes 18 to 24 hours. The tube is left in place for this time. You will be asked to keep a diary of your child's activity during the study. The doctor will use the diary to compare the computer reading with your child's activity.

What happens before a pH probe study?

  • Your child must have an empty stomach for a pH probe study. With the exception of water, apple juice and/or breast milk (which is allowed up to two hours before the procedure), your child should have nothing to eat or drink for four hours before the pH probe study.
  • Some medications can interfere with a pH probe study. Please talk to your doctor a week before the study to discuss what medication can and cannot be given beforehand.

What happens during a pH probe study?

  • The nurse will check your child's height to determine where to place the tube. The nurse will then pass a tube through your child's nose into the stomach. You may stay with your child while the tube is passed.
  • Infants and young children will be snuggled in a blanket to help them to feel secure and stay still while the tube is being passed. Older children may prefer to sit in a chair while the nurse passes the tube.
  • Passing the tube may cause your child to cough, sneeze, or gag. This feeling will pass after the tube is taped in place. Once in place, the tube should not bother your child.
  • Once the tube is taped in place, your child will have an x-ray to check the exact position of the tube. Depending on the x-ray results, the tube may have to be re-taped.
  • Special sleeves may be put on infants and small children to prevent them from bending their elbows and pulling out the tube.
  • Younger patients are usually admitted to the hospital after the tube is inserted. Occasionally, older children can go home with the tube in place.
  • You will be asked to write down what your child is doing while the tube is in place, such as eating, walking and coughing. Your child's nurse will explain exactly what needs to be written down to help with the study.
  • The tube will be removed the next day by a member of the gastroenterology staff. Removing the tube takes less than a minute and does not hurt.

How will we be informed of the results?

When the tube is removed, a Boston Children's gastroenterology doctor will interpret the results recorded by the computer and give them to your child's primary doctor. Call your child's primary doctor one week after the study for the results.

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