What is hydronephrosis (water in the kidney)?
The kidney drains urine down a tube to the bladder. When the flow is slowed, urine collects and the kidney looks swollen on an ultrasound. This is called hydronephrosis. It may come from a narrowing where the kidney joins the tube (PUJ obstruction), from urine flowing backwards (reflux), or, in boys, from a valve in the urine channel. Often no serious cause is found.
How it is found
- On the mother's ultrasound during pregnancy, or on a baby's first scan.
- After a urine infection or fever in a child.
- Rarely, with belly pain or a lump.
What happens next
- A repeat ultrasound after birth, and sometimes further scans to see how well each kidney works and drains.
- Mild swelling is watched with scans over time; many settle by themselves.
- Some children take a low dose of antibiotic to prevent infection while being watched.
- If the kidney is blocked and function is falling, a pyeloplasty repairs the narrowing. It can be done by open or laparoscopic surgery.
Go to a hospital promptly if
- A child with known kidney swelling has fever, vomiting or poor feeding.
- A newborn boy has a weak or dribbling urine stream.
Common questions
Does it mean the kidney is damaged?
Not necessarily. Tests tell how well the kidney works; the swelling on its own does not answer that.
Will my child need an operation?
Only some do. The scans and follow-up decide.
This page is for general information for parents. Every child is different: after examination and tests, an experienced paediatric surgeon decides the condition and the method of treatment. So for any problem, please consult a registered paediatric surgeon.