Antenatal Hydronephrosis
What Antenatal Diagnosis means?
Antenatal diagnosis or diagnosis of disorders while the baby is still in mother’s womb is the cutting edge of medical science. The once opaque womb has been rendered transparent due to free availability of high resolution ultrasound. Two decades back pediatricians and pediatric surgeons used to get frustrated when they used to see a baby with a severe congenital malformation. They used to feel that “I wish I was there earlier”. But now a large number of these anomalies are diagnosed before the baby is born
Ultrasound typically can pick up structural abnormalities in the developing babies especially after 16 weeks once the miniature organs are in place. As expected the specificity is more as the baby grows bigger. This has generated a whole new group of diseases- “Antenatally diagnosed disorders” or we call them “Unborn Patients”
Kidney abnormalities are one of the most common antenatal disorders, found in approximately 1% of all fetuses but the good part is that in up to 80% of them it may represent transient changes in form of slight swelling which goes away by itself  either before or after birth.
The major groups of anomalies 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.
Definition of Antenatal Hydronephrosis?
Antenatal hydronephrosis refers to fluid-filled enlargement of the kidney detected before birth in the fetus by ultrasound studies. Hydronephrosis can be detected as early as the 15 weeks of pregnancy. In most instances this diagnosis will not change obstetric care, but will require careful follow-up and possible evaluation & surgery during infancy and childhood.
What causes antenatal hydronephrosis?
Possible causes of antenatal hydronephrosis include:
  • Blockage: this may occur at the kidney in the Ureteropelvic junction (UPJ/ PUJ), at the bladder in the ureterovesical junction, or in the urethra (posterior urethral valve).
  • Reflux: Vesicoureteral reflux occurs when the valve between the bladder and the ureter does not fuction properly, permitting urine to flow back up to the kidney when the bladder fills or empties. Most children (75%) outgrow this during childhood but need daily antibiotic prophylaxis to try to prevent kidney damage before they outgrow the reflux.
  • Duplications: perhaps 1% of all humans have two collecting tubes from a kidney. These may show up on fetal ultrasound. Occasionally patients with duplication have a ureterocele, which is a balloon-like obstruction at the end of one of the duplex tubes.
  • Multicystic kidney: T his is a nonfunctional cystic kidney.
  • No significant abnormality: Many of these dilated kidneys prove to be normal after delivery.

Ureteropelvic Junction Obstruction

Posterior Urethral Valves

Vesicoureteral Reflux

UPJ obstruction: blockage at the left ureteropelvic junction (where ureter joins to the kidney)
Posterior urethral valves: blockage at the outlet of the bladder
Vesicoureteral reflux on the left: flow of urine back up ureter causing dilated ureter and kidney

Multicystic Kidney

Ureteral Duplication and Ureterocele

Multicystic kidney on the left: kidney may be large, leading to detection on ultrasound
Duplication of ureters on both sides with ureterocele (seen where ureter joins bladder) on left causing bolckage
How is antenatal hydronephrosis managed?
Most cases of hydronephrosis diagnosed during pregnancy are just followed with ultrasound, monitoring the growth of the fetus and the condition of the kidneys. In these cases, a routine, normal delivery can be performed. Rarely, in a fetus with severe obstruction of both kidneys and insufficient amniotic fluid, drainage of the kidneys or bladder by tube or operation may need to be done. In these babies, however, the kidneys are often very abnormal and do not function properly regardless of treatment.
What is done to evaluate the hydronephrosis after the baby is born?
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)
What can be done to treat the hydronephrosis?
The treatment of antenatal hydronephrosis depends on the underlying cause. Infants and children with who have vesicoureteral reflux are managed with antibiotics and surveillance with periodic ultrasounds and voiding cystograms. 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 controversial: the multicystic dysplastic kidney doesn't work, but the opposite kidney is usually normal. Some urologists recommend removal, whereas others do not remove the dysplastic kidney unless its large size causes problems or unless there is a question of tumor or blockage
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