Hydronephrosis in Children

Hydronephrosis develops when the kidneys are stretched from being filled with too much urine. It mostly occurs in babies born with abnormalities that lead to the condition, although the cause of these anomalies has not been found. It can also occur in childhood and affects boys five times more often than girls. The severity of hydronephrosis ranges from mild to life-threatening.

Causes

• Several types of obstructions in the urinary tract result in hydronephrosis. A ureter with an abnormally narrow top can lead to a blockage in the area where the ureter and kidney meet, known as the ureteropelvic junction, which is the most common cause of hydronephrosis. Another common type of obstruction occurs in the ureterovesical junction where the ureter meets the bladder. Blockages can also develop in the urethra, or tube, that empties the bladder. A condition known as vesico-ureteral reflux, in which urine in the bladder reenters the ureters and sometimes the kidneys as well, also causes the kidneys to stretch. Stones, surgery or a urinary tract injury can lead to hydronephrosis as well.

Symptoms

• Children with mild or sometimes moderate cases of hydronephrosis do not usually exhibit any symptoms. Bleeding, pain and infections can occur in severe cases that affect kidney function, but might not show up for months or even years after the condition is originally detected. Mild cases and some moderate cases generally clear up without treatment within a child's first year, while severe cases could require surgery.

Diagnosis Before Birth

• A routine prenatal ultrasound can reveal the earliest signs of obstruction that could lead to hydronephrosis. A pediatric urologist conducts more detailed ultrasounds to find the cause of the blockage and monitors fetal kidney function by measuring the fetus, kidneys and amniotic fluid levels. The urologist classifies the condition as mild, moderate or severe and determines whether a severe case occurs in one kidney, or unilaterally, or in both kidneys, or bilaterally. The urologist will then look for anomalies that could lead to hydronephrosis, such as a swollen pelvic region, reduced levels of amniotic fluid or a distended bladder.

Diagnosis After Birth

• In newborns and kids, an X-ray of the bladder called voiding cystourethrogram, or VCUG, taken as the bladder fills and empties, can detect a backwash of urine into the ureters and kidneys and any blockages in the urethra. X-rays also show how well the bladder functions. A renal ultrasound shows the shape and size of the kidneys, as well as any obstructions or anomalies. An intravenous polygram, or X-ray, of the bladder, kidneys and ureters allows doctors to determine how well the kidneys function. The severity of obstruction in the kidneys can be measured using a renal scan.

Treatment

• Treatment for mild cases of hydronephrosis usually only involves monitoring the condition through renal ultrasounds and VCUG X-rays until it clears up. Infant monitoring generally begins within two to three months after birth. Babies with moderate to severe cases detected before birth receive antibiotics shortly after birth. Imaging tests at one to three months help doctors find the cause and decide whether to perform surgery to remove the blockage or relieve reflux. Severe cases usually require surgery, although it might be necessary in moderate cases as well. Fetuses facing a life-threatening risk due to low amniotic fluid and a blockage in the urethra require fetal surgery. This surgery involves draining the bladder with a shunt and carries risks such as preterm labor, infections and bleeding. Even when this procedure is successful, most infants need additional surgery after birth to help empty the bladder and ensure proper kidney function.