After a child has been treated for a urinary tract infection with fever, many parents ask the same question: "Does my child need a reflux test?" One hospital recommends the test straight away; another looks at an ultrasound and suggests waiting. Online, you will find both "not needed after a first infection" and "always needed".
The short answer is that current international guidelines no longer test every child after a first UTI; they select the children for whom the test is most likely to help. Because the selection rules differ a little between countries, explanations can differ between hospitals. This guide sets out which tests are done after a UTI, when a reflux test is recommended, and what matters if you decide not to test.
Three tests are usually involved after a UTI
The tests done after a UTI answer different questions. Knowing what each one is for makes it easier to follow what your doctor explains.
| Test | What it shows | How it is done |
|---|---|---|
| Renal ultrasound | Structural problems: whether the kidneys or ureters are dilated (hydronephrosis), kidney size and shape, and the bladder | Gel on the tummy and an ultrasound probe. Painless, no radiation |
| Reflux test (VCUG) | Whether urine flows back from the bladder towards the kidney, how much (the grade), and the shape of the bladder and urethra | A thin tube is passed into the bladder through the urethra, the bladder is filled with contrast, and X-ray pictures are taken while the child passes urine |
| DMSA scan (nuclear medicine kidney scan) | During the infection, whether it has reached the kidney tissue (pyelonephritis); a few months later, whether a scar has been left; and how much each kidney contributes | A tracer is given into a vein and pictures are taken a few hours later. It may be done during the infection to confirm pyelonephritis, or a few months afterwards to look for scarring |
The formal name of the reflux test is the voiding cystourethrogram; most parents simply call it the reflux test, and so does this guide — reflux test (VCUG).
One point matters most: a normal ultrasound does not mean there is no reflux. Ultrasound looks for structural problems; reflux is shown by the reflux test. That is why most guidelines start with an ultrasound and then decide, from its result and the child's circumstances, whether a reflux test is needed.
Why not test every child for reflux?
In the past, most children had a reflux test after their first UTI. The approach has changed, for three main reasons.
First, the test itself is a burden. It needs a tube passed into the bladder and involves radiation. It is not easy for a child, or for a parent.
Second, much of the reflux it finds is low grade and often improves on its own as the child grows. Knowing about such reflux may not change what is done.
Third, there is not yet enough evidence that finding reflux in itself improves the child's outcome. It is true that reflux makes it easier for infection to reach the kidney. But it has not been clearly shown that testing every child, finding reflux and managing it leads to fewer kidney scars or better long-term kidney function. So the guidelines have moved towards testing the children who stand to gain the most from it.
That does not mean the reflux test is unnecessary. It is still recommended for the children below.
When a reflux test is recommended
The rules differ a little between national guidelines, but some situations appear in all of them.
- An abnormal ultrasound — dilated kidneys or ureters, a kidney of different size or shape, or a bladder abnormality.
- Another UTI with fever — one infection may be chance, but repeated infections make an underlying cause more likely.
- An "atypical" UTI — infection with an organism other than E. coli, a severe illness such as sepsis, or slow improvement more than 48 hours after treatment started. A weak urine stream or a lump felt in the tummy also count.
The biggest difference is in young infants after a first infection.
| Guideline | Reflux test after a first febrile UTI |
|---|---|
| European Association of Urology / European Society for Paediatric Urology (EAU/ESPU) | Consider it for febrile UTI under 1 year, atypical or recurrent infection, or an abnormal ultrasound |
| National Institute for Health and Care Excellence (NICE, UK) | Under 6 months: for atypical or recurrent infection or an abnormal ultrasound. 6 months to 3 years: not routine, but considered for dilatation on ultrasound, poor urine flow, a non-E. coli infection or a family history of reflux |
| American Academy of Pediatrics (AAP, 2026) | Not routine if the ultrasound is normal. Considered for an abnormal ultrasound or a second febrile UTI, among others |
This is why the same child can be told "let's test" in one place and "let's wait" in another. Neither is simply wrong; they draw the line in different places between the burden of the test and the risk of missing something. It is reasonable to ask your doctor why they have made their recommendation.
If a brother, sister or parent has reflux, please mention it. Reflux in the family makes it more likely in the child.
How is the reflux test done?
The reflux test (VCUG) is usually done after the UTI has been treated and the urine is clear. Roughly:
- A thin tube (catheter) is passed through the urethra into the bladder.
- The bladder is slowly filled with contrast through the tube.
- When the bladder is full, the child passes urine while X-ray pictures show whether urine travels up towards the kidneys.
Children may find the catheter uncomfortable and cry. Whether a parent can stay varies between hospitals, so it is worth asking beforehand. Some stinging when passing urine for a day or two afterwards is common and settles on its own. If your child develops a fever after the test, contact the hospital.
Some hospitals use a contrast-enhanced voiding ultrasound (ceVUS) instead of X-rays, or a nuclear medicine cystogram. The tube is still passed into the bladder, and the question being answered is the same.
If you decide not to test
Deciding to watch rather than test goes together with a promise: check quickly the next time there is a fever.
If your child has a fever without cold symptoms, do not put off a urine test. Young children who cannot yet talk may have no symptom other than fever. It helps to agree in advance where the urine test will be done.
Constipation, holding on to urine for a long time, or sudden urgent needs to pass urine are worth managing too. Bladder and bowel habits are an important cause of repeated UTIs, and dealing with them helps whether or not there is reflux.
And if another UTI with fever occurs, the reflux test is discussed again. Not testing the first time does not mean the chance has been missed.
Frequently asked questions
If the ultrasound is normal, is there no reflux?
Not necessarily. Reflux can be present with a normal ultrasound. However, reflux found in children with a normal ultrasound is often low grade, which is why some guidelines do not routinely do a reflux test when the ultrasound is normal.
Is the reflux test risky for my child?
It is not a high-risk test, but there is the discomfort of the catheter, radiation exposure and, occasionally, an infection afterwards. That is why the current approach is to test the children who really need it.
If there is no reflux, will UTIs stop?
No. UTIs can recur without reflux, because there are other causes such as constipation and bladder habits. The rule of testing urine when there is a fever applies just the same.
If reflux is found, does my child need surgery straight away?
Usually not. Depending on the grade, the child's age, the state of the kidneys and bladder and bowel habits, the choice is between watching, preventive antibiotics and surgery. Low-grade reflux often improves with growth.
When is the DMSA scan done?
The timing depends on the purpose. During or just after the infection, the scan can show whether infection has reached the kidney tissue (pyelonephritis). Changes seen at that stage may be temporary inflammation, so they cannot be taken as a scar. To see whether a scar has been left, the scan is usually repeated a few months after the infection. Not every child needs it; it is mainly considered after repeated or atypical infection or an abnormal ultrasound.
The testing criteria of the three guidelines (EAU/ESPU, NICE, AAP 2026) and the evidence behind them are compared in detail here.
VUR guidelines, Part 1 — Who should be investigated for reflux?
Vesicoureteral Reflux, Part 3 — How pyelonephritis leaves a scar on the kidney
Written for clinicians.
References
- EAU Guidelines on Paediatric Urology. Chapter 12, Urinary tract infections in children; Chapter 17, Vesicoureteric reflux. European Association of Urology, 2026 edition. uroweb.org
- National Institute for Health and Care Excellence. Urinary tract infection in under 16s: diagnosis and management. NICE guideline NG224. nice.org.uk/guidance/ng224
- Alverson BK, Hains DS, Downs SM, et al. Clinical practice guideline for the diagnosis and treatment of urinary tract infection in children from 8 days to 5 years of age. Pediatrics. 2026;158(4):e2026078565. publications.aap.org
- Gnech M, 't Hoen L, Zachou A, et al. Update and summary of the European Association of Urology/European Society of Paediatric Urology paediatric guidelines on vesicoureteral reflux in children. Eur Urol. 2024;85(5):433-442. doi:10.1016/j.eururo.2023.12.005