Pediatric – Hydronephrosis
What is Antenatal Hydronephrosis?
Antenatal (before birth) hydronephrosis (fluid filled enlargement of the kidney) is detected in the fetus by ultrasound studies performed as early as the first trimester of pregnancy. In most instances this diagnosis will not change obstetric care, but will require surveillance and possible surgery during infancy and childhood.
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.
Other causes include the following:
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)
Several studies may need to be performed to evaluate the kidneys:
Ultrasound (done during the newborn period)
Voiding cystourethrogram (to exclude vesicoureteral reflux, a cause of 25-30% of antenatal hydronephrosis
Diuretic renal scan (to evaluate kidney function)