This leaflet is to provide parents and carers information about DMSA scans including why this scan has been advised for your child, what the scan involves and advice for before and after the scan.
What is a DMSA scan?
A DMSA scan will identify the position and shape of your child’s kidneys location and will assess how well one kidney is functioning (working) compared to the other one. DMSA scans are also used to identify any scarring on the kidney which can, for example, be a consequence of urine infections.
A chemical substance, called an isotope, is given by injection into one of your child’s veins. The scan is named after the chemical ‘dimercapto succinic’ acid (DMSA for short), to which the isotope is attached. It takes a few hours for the isotope to be absorbed by the kidneys where it then emits (gives out) a type of radiation called ‘gamma rays’. Your child will lay on a scanning bed and a camera will then be used to detect the gamma rays and turn them into pictures. It is important that your child lays still to achieve the clearest images. Healthy kidney cells take up the DMSA and emit gamma rays which show up brightly on the images produced. Kidney cells that are damaged take up less, or none, of the DMSA and do not emit as many gamma rays and so, on the images produced, these areas are less bright or not seen at all.
Before the appointment
- If your child experiences a urinary tract infection whilst waiting for their DMSA scan appointment it is important that you inform us (telephone numbers are at the end of this leaflet). To ensure reliable results, in most cases, the scan will be deferred until 3 months after the urine infection
- There is no need for your child to fast (‘starve’) for this test. To achieve the best images it is helpful that your child is well hydrated so, unless your child has an underlying problem which means they have to restrict their fluid intake, please encourage your child to have plenty of drink of the day of the scan.
- A tube of local anaesthetic cream (‘EMLA’ cream) may be sent to you in the post with your appointment letter. This cream needs to be applied one hour before the appointment onto four areas, each covering a vein. Apply onto the back of both of your child’s hands where you can see a vein and cover with the plasters included in the pack. Repeat on the inside of their arms over the bend of the elbow. Although you are asked to put the cream in four places, this does not mean your child will have four injections; it is to help the nurse choose which vein is the best.
- There is a small risk that the isotope given to your child could harm an unborn baby. Therefore if you are pregnant or think you could be pregnant, please call us before the appointment is due for further advice as it may be necessary to reschedule the appointment.
- If your daughter is 12 years or over we will ask her about her periods and any possibility that she could be pregnant.
- If your child is apprehensive about needles or scans please inform us without delay before the day of the appointment so we can advise on how to prepare your child or amend arrangements for the appointment.
Preparing your child
Research has shown that children cope much better with hospital procedures if they are well prepared and informed of what is going to happen. It is therefore important for you to talk to your child and explain in a simple and positive manner about what will happen during their visit to the hospital. Some terms that may help when preparing your child could be:
- magic cream (EMLA). This cream stops the injection from stinging too much.
- “while you are having your scan it is important to lie very still so that we do not get fuzzy pictures”
- lying still for a story can be practiced at home; remember to bring your book in with you. Playing ‘sleeping lions’ can be a fun way to practice lying still.
- it may be possible for your child to watch a DVD whilst lying still for imaging; you could bring one with you.
What to do if you cannot attend the appointment
Demand for appointments is high therefore, if the appointment is not convenient it is essential that you contact us without delay so we can both rearrange the appointment for your child and, offer the appointment you are unable to attend, to another patient on our waiting list.
If you do not contact us and then fail to attend the appointment a further appointment will not be offered. Your child’s consultant or GP will be informed.
It is important that the adult accompanying your child for their DMSA scan has ‘parental responsibility’ that is, legal rights, responsibilities, duties, power and authority to make decisions for your child. If the person accompanying your child does not have parental responsibility the scan may need to be rearranged.
At the appointment
The DMSA scan takes place in the nuclear medicine department. Young children may be asked to attend one of our children’s clinics before arriving at the nuclear medicine department so that one of our specialist children’s team can insert a temporary tube into the vein (called a ‘cannula’) which is then used to administer the isotope through. Please ensure that you arrive promptly at the appointment time; arriving late may result in the appointment needing to be re-scheduled.
On arrival your child will be weighed so the correct dose can be calculated.
Once the isotope has been injected, the needle is immediately removed.
It takes about four hours for the kidneys to take up the maximum amount of the DMSA so, to obtain the best scan pictures, you will be able to leave the department and come back three to four hours later. There are no restrictions for your child in between the injection and the scan but it is helpful for your child to drink well as this improves the quality of the scan.
It is essential that you return to the department on time to prevent the scan being delayed or cancelled.
When you return your child will be shown to a room with a scanning bed. There are two large rectangular camera’s; one under the scanning bed and one above the bed (often only the one under the bed needs to be used to get the scan pictures) and there is a small screen on which the scans of the kidneys can be seen. The nuclear medicine team also has another big computer and screen for storing the information from the scans.
Your child will be asked to lie on the scanning bed, which can be moved, so that the technician can get the scan in the right position. It is necessary for your child to keep very still while the scans are taken. Unfortunately, if your child moves, we may have to start that picture again. Each scan takes five minutes.
The first scan is taken with the camera under the couch and then moves to either side. It may seem big but it does not touch your child. You will be able to stay with your child at all times and you may hold their hand. They may also bring a soft toy or a book can be read to them during the scanning process.
Sometimes another scan may be taken with the camera over the abdomen but this is not always necessary.
Taking all the pictures usually takes approximately 45 minutes. Once all the pictures have been taken you and your child may go home. A consultant radiologist will send a report about the scan’s findings to your child’s care team.
For the 24 hours following the appointment
The radioactive substance lasts for only a short period of time and has usually disappeared from the body within 24 hours. During this time:
- Encourage your child to take plenty of drink as this will help the isotope to pass out of their body quicker.
- Toilet trained children should be encouraged to go to the toilet regularly. Hands must be washed thoroughly with soap and water.
- If your child uses a potty, wash the potty and hands thoroughly with soapy water.
- If your child wears nappies or pads, change them frequently and remember to wash hands thoroughly with soap and water.
- If you are pregnant or think you may be pregnant, you should try to avoid contact with your child’s bodily fluids (urine, faeces and vomit) for 24 hours as much as possible and otherwise be thorough with hand washing.
Your child should continue to take any regular medications they receive as normal.
Risks and radiation
Gamma rays are one type of ionising radiation. We are all exposed to ionising radiation in our day to day lives; for example, it is in some construction materials and it seeps from the ground into buildings, when we eat certain foods and when we take a flight.
The isotope used in a DMSA scan contains a small amount of radioactivity, and the radiation from this will be similar to the amount your child normally experiences from a few months of natural background radiation.
The isotope becomes inactive in the hours after the scan and is passed out of your child’s body via their urine hence the precautions advised above in section ‘For the 24 hours following the appointment’.
There are no side effects from the scan itself and the isotope will not interfere with any medication that your child is taking.
Are there alternatives to a DMSA scan?
Although there are other tests (eg ultrasound and CT scans) which can assess the shape and size of your child’s kidneys, they are not able to assess kidney function. Understanding kidney function will be used to plan your child’s treatment.
For further information
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Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge
Telephone +44 (0)1223 245151