Kidney Dilation in Newborn Babies

Kidney dilation is one of the most common pathologies in newborn babies. Because of that, we're going to tell you everything you need to know in this article.
Kidney Dilation in Newborn Babies

Last update: 13 December, 2019

In this article, we’re going to tell you everything you need to know about kidney dilation in newborn babies.

Kidney dilation, or hydronephrosis, in newborn infants is common. Many babies are born with this problem, but it often goes away on its own. However, if it doesn’t, surgery is the only way to remove it completely.

Kidney dilation in newborns

Kidney dilation in newborn babies is a condition that causes changes in the kidneys, pelvis and calyxes, and in the body tissue itself. This comes as a result of an obstruction in the joining of the renal pelvis and ureter. The obstruction can have several causes. Kidney dilation is when these organs don’t do their job correctly – the job of filtering waste from the blood to form urine.

In most cases, hydronephrosis shows no symptoms. However, pain, discomfort in the kidney area, blood in the urine, or infection are some of the most common signs, depending on the cause of the obstruction. Doctors will prescribe antibiotics in the case of infection.

Also, radical surgical treatment, i.e., the removal of the kidney, is the best option when the kidney isn’t functioning at all or has little hope of being able to carry out its natural functions.

A less drastic surgery is to resolve the problem of the obstruction and prevent progressive deterioration of the kidney tissue. Fortunately, you don’t have to worry too much, as the percentage of children who need surgery is very small.

This pathology can affect either one kidney or both. As you can imagine, it’s always better to detect dilation during pregnancy, as this way doctors will know about the problem at birth and will be able to deal with it accordingly.

In most cases of hydronephrosis, there is automatic improvement during the first two years of the child’s life.

Kidney Dilation in Newborn Babies

A very common condition in newborns

Unfortunately, kidney dilation is one of the most noticeable abnormalities in the fetus, especially during a prenatal ultrasound. In most cases, there’s no explanation for the cause of this condition. Because of this, the only real treatment is to monitor the child’s kidney.

Doctors rate hydronephrosis in a child from 1 to 4, from mild to severe. The mild version can easily disappear at birth, or before 2 years of age. The doctor may prescribe a small preventive daily dose of antibiotics during this time in order to prevent infection and kidney damage.

In some cases, it’s also important to carry out tests in order to determine if hydronephrosis is being caused by other conditions, such as urine reflux or obstruction. Infants with these conditions should be monitored and treated regularly with specific medical care.

What causes kidney dilation?

We’ll now tell you what the most common causes of kidney dilation in newborns are.

1. Obstruction of the ureteropelvic junction

This complication usually affects only one kidney and, in most cases, affects male fetuses. It’s almost always congenital and is the cause of primary hydronephrosis. It’s caused by an obstacle in the ureter. Doctors will confirm the diagnosis by a specific test after the child is born.

2. Obstruction of the posterior urethral valve

This second complication is potentially serious, depending on the degree of obstruction. A membrane in the urethra slows, or completely blocks, the flow of urine, and this, in turn, affects the entire urinary system. There is a dilatation of the bladder with a thickening of its walls, and the dilatation of the kidney and ureter. The name given to this is megaureter.

Kidney Dilation in Newborn Babies

3. Vesicoureteral reflux

This third and final cause is an increase in the urine contained in the bladder going towards one or both kidneys. This complication is the result of a physiological abnormality in the anti-reflux system.

In most cases, it’s caused by an insufficient angle at the point where the ureter goes into the bladder. This prevents the ureter and the anti-reflux system from closing completely at the same time as the bladder contracts.

Before we finish, we’d like to remind you that, since the kidneys are visible from the 17th or 18th week of pregnancy, many medical centers will offer data on kidney dilation in newborns before birth. In any case, you shouldn’t worry too much, as most cases can be treated with medical intervention.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

    • Madariaga Dominguez, L., & Ordóñez Alvarez, F. Á. (2014). Manejo de las anomalías renales y del tracto urinario detectadas por ecografía prenatal. Uropatías obstructivas. Protoc Diagn Ter Pediatr. AEP, (1), 225–239.
    • Sarisol García-Pérez, C., Cordero-González, G., Reproducción, P. Y., Artículo, H., & Revisión, D. (2011). Función renal en el recién nacido. Medigraphic25(3), 161–168. Retrieved from
    • Melgosa Hijosa, M., Fons Moreno, J., Paz Madrid, L., Hijosa, M. M., & Moreno Enfermedades, F. J. (2014). ENFERMEDADES RENALES MÁS FRECUENTES EN EL PERIODO NEONATAL. Asociación Español de Pediatría1, 207–24. Retrieved from
    • National Institute of Diabetes and Digestive and Kidney Diseases. Hidronefrosis en recién nacidos. Octubre 2019. U.S. Department of Health and Human Services. National Institutes of Health.
    • National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms and causes of bladder infection in children. Abril 2017. U.S. Department of Health and Human Services. National Institutes of Health.
    • Asociación Española de Pediatría. Dilatación del riñón. Me han dicho que mi bebé la tiene. Abril 2019.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.