What is Hydronephrosis?

Hydronephrosis is a condition of the urinary tract and happens when there is too much fluid in one or both kidneys. The urinary tract includes the kidneys, ureters, bladder and urethra. It helps the body filter and remove waste and extra fluid. With hydronephrosis, urine (pee) can’t drain from the kidneys to the bladder. This makes one or both kidneys swell with extra fluid.

Other names for hydronephrosis are urinary tract dilation, pelviectasis and caliectasis.

Hydronephrosis in infants may appear before a baby is born. About 1% to 5% of prenatal ultrasounds show signs of hydronephrosis in pregnancy.

Most cases of fetal hydronephrosis will resolve on their own. A pediatric urologist should be involved in your child’s care. They will do more testing, including a hydronephrosis ultrasound, after the child is born. The ultrasound will see if another condition is causing the hydronephrosis. A small percentage of children with hydronephrosis need surgery if there is a blockage in or near the kidneys.

Hydronephrosis Causes

There are several possible causes for hydronephrosis:

• Blockage: There may be an obstruction or blockage in some part of the urinary tract. For example, it may happen at the ureteropelvic junction (UPJ), ureterovesical junction (UVJ), or posterior urethral valve (in boys) (Figure 1).
• Reflux: There may be backflow of urine from the bladder, also called vesicoureteral reflux.
• No specific cause: There may not be a known cause for hydronephrosis. It will go away on its own.

Figure 1: Shows two possible areas of obstruction in the urinary tract that may lead to hydronephrosis.

Hydronephrosis Diagnosis

Pediatric hydronephrosis can be found before birth or after birth. Fetal hydronephrosis is the most common urinary tract issue found during a routine ultrasound. Hydronephrosis is not a diagnosis. It just means there is extra fluid in the kidneys. A more accurate diagnosis can happen after a child is born.

Children born with hydronephrosis (congenital hydronephrosis) often receive an ultrasound after birth (Figure 2). The hydronephrosis ultrasound provides more information. It can help confirm if the infant has unilateral hydronephrosis (in one kidney) or bilateral hydronephrosis (in both kidneys). The ultrasound also will detect if the infant has mild, moderate or severe hydronephrosis. This scale is based on how much fluid drains from the kidneys. More detailed hydronephrosis grading systems exist for health professionals and researchers.

Figure 2: Ultrasound of a normal kidney (left) and a severe hydronephrosis kidney (right). The dark spots show the extra fluid.

Some infants or young children with hydronephrosis need more testing. They may need magnetic resonance imaging (MRI), a special X-ray or a renal scan. Diagnosing an underlying condition can help find the best treatment options, if needed.

Hydronephrosis Symptoms

Newborns and infants usually don’t have any congenital hydronephrosis symptoms. Older children with moderate or severe hydronephrosis may:

• Have frequent urinary tract infections (UTIs) with a fever.
• Have some pain in their side or abdomen area.
• See blood in the urine.

Hydronephrosis Treatment

Treatment for hydronephrosis depends on how severe it is and the cause. The three main treatment options include:

• Observation: Many cases of mild and moderate hydronephrosis go away on their own without treatment. Infants will have an ultrasound before and after birth, so their provider can see if they need more testing. Their provider also will watch for any changes in the kidneys over time.
• Antibiotics: Some children may benefit from taking antibiotics to prevent or treat UTIs.
• Surgery: Surgery is reserved for severe hydronephrosis. Surgery for hydronephrosis can help when there is an obstruction that causes symptoms or kidney damage. Depending on the obstruction and underlying condition, different procedures can help restore the free flow of urine. These procedures include a full range of minimally invasive and robotic-assisted laparoscopic techniques. They use the most advanced DaVinci surgical robotic system.

Hydronephrosis Prognosis

For mild and moderate hydronephrosis, it is very likely the condition will improve over time on its own. It should not cause future damage to the kidneys. For severe hydronephrosis, providers may need to watch it more closely. The goal is to prevent any hydronephrosis complications that put the kidneys at risk.