Antenatal Hydronephrosis - MITR

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Antenatal diagnosis (also called Prenatal Diagnosis) refers to diagnosis of congenital disorders while the baby is still in mother’s womb. This is the cutting edge of medical science. The once opaque womb has become accessible and transparent due to advent of high resolution ultrasound. Till some years back, pediatricians and pediatric surgeons used to feel helpless when they used to see a newborn with a severe congenital defect. In the present era, a large number of these anomalies are diagnosed even before the birth of the baby.

Ultrasound can diagnose structural abnormalities in the fetus after 16 weeks once the miniature organs are in place. As expected the specificity increases as the baby grows bigger. This is a whole new group of diseases – “Antenatally diagnosed disorders” or we call them “Unborn Patients”

The major types of defects seen in unborn babies are kidney abnormalities (swelling, absent kidney), hydrocephalus (excessive brain fluid leading to pressure damage on brain), cardiac anomalies, neural tube defects, certain chromosomal disorders, lung anomalies, tumors and cysts in belly.

Kidney abnormalities are one of the most common antenatally diagnosed disorders, found in approximately 1% of all fetuses but the good part is that in up to 80% of them it may be a very mild transient swelling which resolves either before or after birth.

Definition of Antenatal Hydronephrosis

Antenatal hydronephrosis refers to fluid-filled swelling of the kidney detected before birth in the fetus by ultrasound studies. Hydronephrosis can be diagnosed as early as the 15 weeks of pregnancy. In most instances this diagnosis does not change obstetric care, but will require careful follow-up and possible evaluation & surgery after birth during infancy and childhood.

Possible causes of antenatal hydronephrosis include:

Blockage:This may occur at the junction of the kidney and the drainage pipe (ureter) a junction called Ureteropelvic junction (UPJ/ PUJ), or at the bladder and the ureter (ureterovesical junction), or in the urethra (posterior urethral valves).
Reflux:Vesicoureteral reflux (VUR) refers to reverse flow of urine from bladder to the kidney. This occurs when the valve between the bladder and the ureter does not function properly, permitting urine flow back up to the kidney when the bladder is full or the child is passing urine. Most children with VUR (75%) will outgrow reflux and stop refluxing during childhood but urinary infections need to be diagnosed and treated early to prevent kidney damage. A low dose daily antibiotic prophylaxis also helps in these children.

Duplications:Presence of double ureters is a common condition and occurs in 1% of all humans. These may show up on fetal ultrasound if any of the tube is swollen. Occasionally patients with duplication have a Ureterocele (balloon-like obstruction at the end of one of the duplex tubes) leading to obstruction to urine flow and a swelling of the kidney.
Multicystic kidney:A nonfunctional kidney looks like a bunch of grapes.
No significant Abnormality:Many of these kidneys with swelling prove to be normal after delivery.

UPJ obstruction: block at the left ureteropelvic junction or UPJ or PUJ (where ureter joins to the kidney)
Posterior urethral valves: block at the outlet of the bladder
Vesicoureteral reflux on the left: flow of urine back up ureter causing dilated ureter and kidney
Multicystic kidney on the left: kidney may be large due to multiple cysts, leading to detection on ultrasound
Duplication of ureters on both sides with ureterocele (seen where ureter joins bladder) on left causing blockage
Management of Antenatal Hydronephrosis

Most cases of antenatal hydronephrosis diagnosed during pregnancy are just followed monthly with ultrasound, monitoring the growth of the fetus and the swelling of the kidneys. In these cases, a normal delivery can be performed. Rarely, in a fetus with severe obstruction involving both the kidneys and insufficient amniotic fluid, drainage of the kidneys or bladder by a catheter tube or operation may need to be done. In these babies, however, the kidneys are often very abnormal and do not function properly in upto 50% regardless of treatment.

Post birth Evaluation

Several studies may need to be performed to evaluate the kidneys:

Ultrasound (done during the newborn period) – for one sided swelling after one week and earlier if both the kidneys are swollen
Voiding or micturating cystourethrogram (VCUG/MCU) is done in selected cases to exclude vesicoureteral reflux and urethral blocks like PUV
Diuretic renal scan may be done to evaluate drainage and kidney function
Blood tests like serum creatinine to evaluate kidney function.

Treatment

The treatment of antenatal hydronephrosis depends on the underlying cause.Vesicoureteral reflux (VUR): Infants and children with who have vesicoureteral reflux are managed with antibiotics and surveillance with periodic ultrasounds and voiding cystograms.
Obstruction: Infants and children with an obstruction or blockage of the urinary tract may require surgical correction.
Babies with hydronephrosis without reflux or obstruction are followed with periodic ultrasounds to monitor the hydronephrosis and the growth of the kidneys.
The management of multicystic dysplastic kidneys is observation as the opposite kidney is usually normal. Non-functioning multicystic kidney is removed only if its large size causes problems or there is a doubt of tumor or blockage.