What is Hydronephrosis?
Hydronephrosis is a condition where one or both kidneys become swollen due to a buildup of urine. The term breaks down into “hydro” meaning water and “nephro” meaning kidney. This swelling occurs when urine cannot properly drain from the kidney into the bladder, often due to a blockage or narrowing along the urinary tract. Hydronephrosis in children can range from mild to severe, and in some cases, may require surgical intervention to resolve the blockage.
Hydronephrosis is often detected in an unborn child during pregnancy, when an antenatal scan reveals swelling in the baby’s kidney. While many cases resolve on their own after birth, some children may need further testing or treatment to ensure their kidneys function normally.
Hydronephrosis in Children: Mild, Moderate, and Severe
Hydronephrosis in children can vary in severity.
- In mild hydronephrosis, there is only slight swelling of the kidney due to a small buildup of urine, and this often resolves on its own without intervention.
- Moderate hydronephrosis involves more noticeable swelling, and while it may require monitoring, it can sometimes resolve without surgery.
- In severe hydronephrosis, the kidney is significantly swollen due to a larger obstruction or blockage, which can affect kidney function and often requires surgical treatment to prevent long-term damage.
What Causes Hydronephrosis in Children?
The most common cause of hydronephrosis in children is a blockage in the urinary tract, which prevents urine from flowing freely. Other causes may include:
- Ureteropelvic Junction (UPJ) Obstruction: A narrowing at the point where the kidney connects to the ureter (the tube that drains urine to the bladder).
- Vesicoureteral Reflux (VUR): A condition where urine flows backward from the bladder into the ureters and kidneys.
- Congenital Abnormalities: Structural issues in the urinary system that develop during foetal development.
- Urinary Tract Infections (UTIs): Chronic or severe UTIs may lead to swelling in the kidneys and require ongoing management.
In many cases, the underlying cause of hydronephrosis is diagnosed through postnatal ultrasounds and other imaging tests.
Symptoms of Hydronephrosis in Children
Most children with hydronephrosis have no symptoms and experience no pain., especially if it is mild. In newborns and infants, hydronephrosis may be detected through antenatal scans or during routine health checks after birth – not because of any particular symptoms.
Hydronephrosis, Hydroureter and Megaureter
Sometimes hydronephrosis is also associated with dilation (enlargement) of the ureter – the tube that carries urine from the kidneys to the bladder. This is called hydroureter, or also known as megaureter. The ureter can become dilated for several reasons:
- Reflux: Urine flows backward from the bladder into the ureter and up toward the kidney.
- Partial Blockage: This can occur at the bladder, making it difficult for urine to drain properly.
- Residual Enlargement: In some cases, the ureter may appear baggy and swollen even after the cause of the problem has resolved.
Hydroureter often accompanies hydronephrosis and may be a contributing factor to the swelling in the kidneys.
Duplex Kidneys: A Special Consideration
A duplex kidney is a congenital condition that occurs in about 1% of children. In this condition, a child is born with two ureters that drain from the same kidney. While most children with duplex kidneys have no symptoms, some may experience issues that require medical attention, such as:
- Urinary tract infections (UTIs) due to improper drainage.
- Vesicoureteral reflux (VUR), where urine flows backward into the kidneys.
- Obstruction in one of the ureters, which may lead to hydronephrosis.
In cases where duplex kidneys cause symptoms or complications, further testing may be needed to assess whether surgical treatment is necessary.
How is Hydronephrosis Diagnosed?
In most cases, hydronephrosis is first detected during routine antenatal scans. After birth, further tests may be required to understand the severity and underlying cause of the condition. Common diagnostic tests include:
- Ultrasound: This is the primary tool used to assess the degree of swelling in the kidneys and ureters.
- Voiding Cystourethrogram (VCUG): This test involves filling the bladder with a dye and using X-rays to track the flow of urine, helping to diagnose vesicoureteral reflux (VUR).
- Renal Scan: A specialised scan to assess how well the kidneys are functioning and to evaluate any blockages in the urinary system.
Your paediatric urologist will recommend the appropriate tests to determine the next steps in treatment.
Does Hydronephrosis Require Surgery?
The treatment for hydronephrosis depends on the severity and the underlying cause of the condition. In most cases, hydronephrosis may resolve on its own without treatment, especially if it was diagnosed during pregnancy. However, in more severe cases where there is a persistent blockage or ongoing kidney swelling, surgery may be required.
Treatment for hydronephrosis generally includes:
- Observation: In mild cases, your doctor may recommend regular ultrasounds to monitor the condition and ensure the swelling resolves over time.
- Surgery: If the hydronephrosis is caused by a blockage, such as a ureteropelvic junction (UPJ) obstruction, a procedure called pyeloplasty may be performed to remove the blockage and restore normal urine flow.
- Hydroureter Surgery: For severe cases of hydroureter, where the ureter is significantly dilated, surgery may be required to improve the drainage from the kidney to the bladder.
For more information on surgery for hydronephrosis, visit our Hydronephrosis Surgery page.
Prognosis for Children with Hydronephrosis
The outlook for children with hydronephrosis depends on the severity of the condition and the underlying cause. Most children with mild hydronephrosis experience full recovery without the need for surgery. Even in more severe cases that require surgical intervention, the long-term outlook is generally positive, with most children having normal kidney function after treatment.
When to Seek Medical Advice
If your child has been diagnosed with hydronephrosis, it’s important to monitor for any potential complications. Contact your family doctor, paediatrician or paediatric urologist if your child experiences:
- Fever, pain, or symptoms of a urinary tract infection (UTI).
- Reduced urine output or difficulty urinating.
- Persistent abdominal or back pain.
Image Gallery for Patient Consultations
Our Paediatric Surgeons may use this image set during your consultation to explain conditions and treatments.
We welcome our referrers and other health professionals in the community to use these as well.
Hydronephrosis
Hydroureter / megaureter
Hydro = water, Ureter is the pipe that drains urine from the kidney to the bladder.
The reason for the ureter to be dilated / swollen can be from some reflux of urine back to the kidney, or from a partial blockage at the bladder. Sometimes it was a problem and no longer, so remains a little baggy.
Duplex kidneys
This happens in about 1% of people, where there are 2 pipes (ureters) that drain from the kidney. Most of the time it doesn’t cause any trouble, and sometimes there are issues that require intervention.
