Lasix Renal Scan

Why do a MAG3?

A Lasix renal scan (MAG3) is a nuclear medicine test that provides pictures of your child's urinary system including the kidneys, ureters and bladder. For a MAG3, your child will be given an injection of a radioisotope and Lasix, a medicine to increase urine output, through an IV. A small tube called a catheter will be placed allowing your child's bladder to stay empty throughout the test. This test shows how well the kidneys are working and if there is anything blocking kidney drainage. This test takes 2 hours.

How Does the Urinary System Work?

Kidneys filter and clean waste from the blood to produce urine (pee). Urine passes out of the kidneys down through the ureters, two thin tubes, which take the urine from the kidneys to the bladder. The bladder holds the urine until it is time to go to the bathroom. Then the urine passes out of the body through the urethra. See below.

What to Expect During a MAG3

Step 1 - IV Placement

  • Your child will change into a hospital gown and lie on their back on a special camera bed.
  • The tech will look for the best place to put the IV, a tiny, plastic straw placed into a vein using a small needle.
  • The tech will clean your child's skin and apply a numbing spray that will feel cold. The IV will be placed into your child's hand, arm or foot. The tech will connect the end of the IV to a bag of water.
    • The water will help keep your child hydrated during the MAG3.
  • During the IV, you are encouraged to comfort your child by standing at the head of the bed and holding your child's hands. Your child can look at a fun toy, iPad, sing a favorite song or take deep breaths as long as they lie still!

Step 2 - Catheter Placement

  • Your child will continue to lie on the table and be asked to:
    • For Girls: make "frog" or "butterfly" legs (knees bent out with feet touching)
    • For Boys: make legs straight on table
  • A tech will clean your child's private area with a special soap called Betadine and apply numbing jelly to the urethra. This will feel cold and wet.
  • A small flexible tube called a catheter will be inserted through the urethra into the bladder and taped to the inside of your child's thigh.
    • The catheter may make your child feel that he/she has to pee, but remember, the catheter will drain his/her bladder.
    • Your child's job will be to lie still and take deep breaths.

Step 3 - Pictures

  • The tech will inject a radioisotope through your child's IV. This medicine allows the doctors to see how well the urine passes through your child's urinary system.
    • Some children say they do not feel anything, others say they have a "cold" feeling inside their body.
  • The camera is placed under the bed your child is lying on and the 50 minutes of pictures will start.
    • Children may be wrapped in a blanket to help them stay still during the pictures.
    • Your child's job will be to lie still for the pictures. Movies will be available for your child to watch.
    • You may sit next to your child during the pictures.
  • 20 minutes into the pictures the tech will give your child Lasix through the IV.
  • After the 50 minutes of pictures, the tech will take the IV and catheter out and your child may put his/her clothes on.

After the Procedure

  • There are no special instructions for your child to follow. Encourage your child to drink lots of fluids and urinate frequently.
  • The results will be sent to your child’s referring doctor. Please follow up with your child’s doctor for results and to ask questions.


  • Bring comfort items from home such as toys, blankets, stuffed animals, books, etc. Having a familiar object can help comfort your child during the procedure.
  • Family presence is the best form of coping for a child in the hospital. We encourage family presence during the MAG3.
  • Women who are pregnant should not be at your child’s bedside during the exam. If this is the case, please arrange for a familiar adult to be present.
  • Siblings are not allowed in the procedure room.

Please make arrangements to have someone stay with them. Toilet-trained siblings aged 2-12 can visit Jack’s Tree House, located on the first floor by the parking structure entrance.

Jack’s Tree House: (313) 745-5365

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