Question: What causes Urine Blockage in Newborns ?
Answer: Many types of defects in the urinary tract can cause urine blockage:
                
- Vesicoureteral reflux (VUR). Most children with VUR are born with a ureter that did not grow long enough during development in the womb. The valve formed by the ureter pressing against the bladder wall does not close properly, so urine backs uprefluxesfrom the bladder to the ureter and eventually to the kidney. Severe reflux may prevent a kidney from developing normally and may increase the risk for damage from infections after birth. VUR usually affects only one ureter and kidney, though it can affect both ureters and kidneys.  - Ureteropelvic junction (UPJ) obstruction. If urine is blocked where the ureter joins the kidney, only the kidney swells. The ureter remains a normal size. UPJ obstruction usually occurs in only one kidney.
                
- Bladder outlet obstruction (BOO). BOO describes any blockage in the urethra or at the opening of the bladder.Posterior urethral valves (PUV), the most common form of BOO seen in newborns and during prenatal ultrasound exams, is a birth defect in boys in which an abnormal fold of tissue in the urethra keeps urine from flowing freely out of the bladder. This defect may cause swelling in the entire urinary tract, including the urethra, bladder, ureters, and kidneys.  - Ureterocele. If the end of the ureter does not develop normally, it can bulge, creating a ureterocele. The ureterocele may obstruct part of the ureter or the bladder.
                
Some babies are born with genetic conditions that affect several different systems in the body, including the urinary tract:
                
- Prune belly syndrome (PBS). PBS is a group of birth defects involving poor development of the abdominal muscles, enlargement of the ureters and bladder, and both testicles remaining inside the body instead of descending into the scrotum. The skin over the abdomen is wrinkled, giving the appearance of a prune. PBS usually occurs in boys, and most children with PBS have hydronephrosisswelling in the kidneyand VUR.  - Esophageal atresia (EA). EA is a birth defect in which the esophagusthe muscular tube that carries food and liquids from the mouth to the stomachlacks the opening for food to pass into the stomach. Babies born with EA may also have problems with their spinal columns, digestive systems, hearts, and urinary tracts.  - Congenital heart defects. Heart defects range from mild to life threatening. Children born with heart defects also have a higher rate of problems in the urinary tract than children in the general population, suggesting that some types of heart and urinary defects may have a common genetic cause.
                
Urine blockage can also be caused by spina bifida and other birth defects that affect the spinal cord. These defects may interrupt nerve signals between the bladder, spinal cord, and brain, which are needed for urination, and lead to urinary retentionthe inability to empty the bladder completelyin newborns. Urine that remains in the bladder can reflux into the ureters and kidneys, causing swelling.

Topic: Urine Blockage in Newborns
Source: NIDDK