Pediatric Urology

Home » Pediatric Urology » Antenatal Hydronephrosis, Causes, Diagnosis, Treatment

Overview

Antenatal (i.e., before birth) hydronephrosis is a condition in which the outflow of urine from the kidney is obstructed, resulting in fluid-filled enlargement. The condition is usually detected by ultrasound, as early as the first trimester of pregnancy.

Antenatal hydronephrosis can be mild, moderate, or severe and it requires monitoring before birth and during infancy and childhood. Occasionally, the kidney appears enlarged (dilated) during antenatal ultrasound yet functions normally after birth.

Causes

The most common cause of antenatal hydronephrosis is a narrowing of the ureter close to the kidney, usually developing before the fourth month of pregnancy.

• Blockage (in the kidney, at the uteropelvic junction [UPJ]; in the bladder, at the uterovesical junction; or in the urethra, due to the posterior urethral valves)
• Reflux (condition in which the valve between the bladder and the ureter allows urine to flow back into the kidney when the bladder fills or empties)
• Duplication anomaly (occurs in 1% of the population and involves two ureters leading from the kidney; one may have an obstruction called a uterocele)
• Multicystic kidney (nonfunctional kidney)

Diagnosis

Antenatal hydronephrosis is usually diagnosed by prenatal ultrasound. The condition may also be diagnosed during an evaluation for a urinary tract infection in infancy.

Treatment

This condition is usually managed by carefully observing kidney growth and function throughout the pregnancy by ultrasound. Low-dose antibiotics may be administered to prevent infection.

Cases of moderate or severe antenatal hydronephrosis may require a surgical procedure to drain urine and prevent kidney damage. Surgery to treat a blockage (called pyeloplasty) has a success rate of 90–95%. However, in many cases (even moderate to severe cases), the condition resolves and does not result in kidney damage. Carefully monitoring kidney growth and function is the preferred treatment unless surgery proves necessary.

After birth, infants continue to require monitoring. Ultrasound is performed to assess kidney function. A cystogram may be performed to determine if urine is backing up into the kidney (reflux). In this procedure, a small tube is inserted through the urethra into the bladder. A contrast agent (dye) is instilled through the tube into the bladder and x-rays are used to detect reflux. Other tests may be performed to assess the function of both kidneys.

In cases of multicystic kidney, the other kidney is usually normal. Removal of the nonfunctioning kidney is not required unless complications (e.g., tumor, blockage, excessive size) develop.

Kidney function in patients with this condition must be regularly monitored (usually by ultrasound performed every 6 months) throughout childhood.

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