Urine Blockage 

in Newborns 

National Kidney and Urologic Diseases Information Clearinghouse 

National 

Institute of 

Diabetes and 

Digestive 

and Kidney 

Diseases 

NATIONAL 

INSTITUTES 

OF HEALTH 

U.S. Department 

of Health and 

Human Services 

The urinary tract consists of 

•	 two kidneys, which filter waste materials and excess water from the blood 

•	 two ureters, which carry urine from the 

kidneys to the bladder 

•	 the bladder, where urine is stored until 

it is released 

•	 the urethra, where urine flows out of 

the body 

We rely on our kidneys and urinary system 

to keep fluids and natural chemicals in our 

bodies balanced. While a baby is developing in the mother’s womb, much of that 

balancing is handled by the mother’s 

placenta. The baby’s kidneys begin to 

produce urine at about 10 to 12 weeks 

after conception, but the mother’s placenta 

continues to do most of the work until the 

last few weeks of the pregnancy. Wastes 

and excess fluid are removed from the 

baby’s body through the umbilical cord. 

The baby’s urine is released into the 

amniotic sac and becomes part of the 

amniotic fluid. This fluid plays a role in 

the baby’s lung development. 

Sometimes, a birth defect in the urinary 

tract will block the flow of urine in an 

unborn baby. As a result, urine backs 

up and causes the ureters and kidneys to 

swell. Swelling in the kidneys is called 

hydronephrosis. Swelling in the ureters 

is called hydroureter. 

Kidney 

Ureter 

Bladder 

Urethra 

Normal urinary tract. 

Hydronephrosis 

Hydroureter 

Swelling in the kidney is called hydronephrosis. 

Swelling in the ureter is called hydroureter. 
Hydronephrosis is the most common problem found during ultrasound examination 

of babies in the womb. The swelling may 

be barely detectable or very noticeable. 

The results of hydronephrosis may be mild 

or severe, but the long-term outcome for 

the child’s health cannot always be judged 

by the severity of swelling. Urine blockage 

may damage the developing kidneys and 

reduce their ability to filter. The blockage 

may also raise the risk that the child will 

develop a urinary tract infection (UTI). 

Recurring UTIs can lead to more permanent kidney damage. In the most severe 

cases of urine blockage, the amniotic sac is 

so reduced that the lack of fluid threatens 

the baby’s lung development. 

Types of Defects in the 

Urinary Tract 

Hydronephrosis can result from many 

types of defects in the urinary tract. 

Doctors use specific terms to describe 

the type and location of the blockage. 

•	 Vesicoureteral reflux (VUR). The 

openings where the ureters empty 

urine into the bladder should work like 

valves to keep urine from backing up 

into the ureters. Sometimes the valve 

doesn’t work properly and urine flows 

back into the kidneys. The urine may 

flow only a short way back into the 

ureters, or it may go all the way back 

to the kidneys, causing the ureters and 

kidneys to swell. VUR may occur in 

only one ureter or in both. Kidneys 

with severe reflux may not develop 

normally, and after birth kidneys 

with reflux may be at risk for damage 

from infections. 

2	 Urine Blockage in Newborns 

•	 Ureteropelvic junction (UPJ) obstruction. The point where the ureter joins 

the kidney is called the ureteropelvic 

junction. If urine is blocked here, only 

the kidney swells. The ureter remains 

at a normal size. UPJ obstruction 

usually only occurs in one kidney. 

•	 Bladder outlet obstruction (BOO). 

BOO describes any blockage in the 

urethra or at the opening of the bladder. The obstruction may occur in 

boys or girls. The most common form 

of BOO seen in newborns and during 

prenatal ultrasound examinations is 

posterior urethral valves (PUV). 

BOO caused by PUV occurs only 

in boys. 

•	 Posterior urethral valves (PUV). In 

boys, sometimes 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. 

UPJ 

obstruction 

Ureteropelvic junction (UPJ) is the point where the 

ureter joins the kidney. 
•	 Ureterocele. If the end of the ureter 

does not develop normally, it can 

bulge, creating what is called a ureterocele. The ureterocele may obstruct 

part of the kidney or the bladder. 

•	 Nerve disease. Urination requires 

coordinated nerve signals between the 

bladder, spinal cord, and brain. Spina 

bifida and other birth defects that 

affect the spinal cord may interrupt 

nerve signals and lead to urine 

retention in newborns. 

Ureterocele 

Bladder 

wall 

Ureter 

Ureterocele. The inset shows a cross-section of the 

ureter bulging into the interior of the bladder. 

Syndromes That May Affect 

the Urinary Tract 

In addition to defects that occur in a single 

spot in the urinary tract, some babies are 

born with genetic conditions that affect 

several different systems in the body. A 

condition that includes multiple, seemingly 

unrelated problems, is called a syndrome. 

•	 Prune belly syndrome (PBS). Occurring only in boys, PBS causes a baby to 

have an enlarged abdomen because 

the normal abdominal wall muscles 

are missing or very weak. The entire 

urinary tract is enlarged, and both 

testicles remain inside the body instead 

of descending into the scrotum. The 

skin over the abdomen is wrinkled, 

giving the appearance of a prune. 

Most children with PBS have 

hydronephrosis and VUR. 

•	 Esophageal atresia (EA). EA is a 

birth defect in which the esophagus 

is incomplete. The esophagus is the 

tube that carries food from the mouth 

to the stomach. About 30 percent of 

babies born with EA will have problems in other body systems, such as 

the heart or urinary tract. 

•	 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. 

3	 Urine Blockage in Newborns 
Diagnosis 

Birth defects and other problems of the 

urinary tract may be discovered before 

the baby is born, at the time of birth, or 

later, when the child is brought to the 

doctor for a urinary tract infection or 

urination problem. 

Prenatal Screening 

Tests during pregnancy can help determine 

if the baby is developing normally in the 

womb. 

•	 Ultrasound. Ultrasound uses sound 

waves to produce a picture on a television screen. A wand gliding on the 

mother’s abdomen directs harmless 

sound waves into the womb. The 

sound waves bounce off the baby 

and back into the wand to create a 

black-and-white image on the screen. 

Ultrasound images can even display 

internal organs within the baby, so 

enlarged kidneys, ureters, or bladder 

may be visible. 

•	 Amniocentesis. In amniocentesis, the 

doctor inserts a needle through the 

mother’s skin into the amniotic sac to 

collect about an ounce of amniotic fluid. The fluid contains genetic material 

from the baby that can be analyzed for 

signs of defects. 

•	 Chorionic villus sampling (CVS). In 

CVS, the doctor collects a small piece 

of tissue from the placenta using a 

needle passed through the mother’s 

vagina and cervix. The placenta has 

the same genetic makeup as the baby. 

Enlarged 

kidney 

Ultrasound allows evaluation of a baby’s internal 

organs, even before birth. 

Most healthy women do not need all the 

tests. Ultrasound examinations during 

pregnancy are routine, although they are 

not always required and rarely influence 

treatment decisions. Amniocentesis and 

CVS are recommended only when a risk of 

genetic problems exists because of family 

history or something detected during an 

ultrasound. Amniocentesis and CVS carry 

a slight risk of harming the baby and mother, or ending the pregnancy in miscarriage, 

so those risks should be weighed carefully 

against the potential benefits of learning 

about the baby’s condition. 

4	 Urine Blockage in Newborns 
Examination of Newborn 

Sometimes a newborn does not urinate as 

expected, even though prenatal testing 

showed no sign of urine blockage. The 

baby may urinate only small amounts or 

not at all. An enlarged kidney may be felt 

during the newborn examination as well. 

Different imaging techniques are available 

to determine the cause of the problem. 

•	 Ultrasound. Once the baby is born, 

ultrasound can be used to view the 

baby’s urinary tract directly for a 

clearer image than could be achieved 

while the baby was in the womb. 

•	 Voiding cystourethrogram (VCUG). 

If the doctor suspects that urine is 

backing up into the ureters or that the 

bladder outlet is obstructed, a VCUG 

may be needed. In this test, a catheter 

is used to fill the child’s bladder with 

warm liquid containing iodine to make 

it visible on an x ray. A video records 

the x-ray images of the bladder as it is 

filled and as the child urinates. The 

video will reveal reflux if the liquid 

enters the ureters and blockage of the 

bladder in the case of an obstruction, 

such as PUV. 

•	 Nuclear scan. A nuclear scan involves 

injecting a very small amount of 

radioactive material, just enough to 

show up using a camera that captures 

gamma rays. The amount of radioactive substance used is determined by 

the child’s weight. The liquid is injected into the child’s bloodstream and 

eventually passes through the kidneys, 

where it is filtered from the blood and 

directed down the ureters to the bladder. The camera may be mounted 

above or below a table where the 

patient lies. The camera passes over 

or under the urinary tract as the child 

lies on the table. 

Later Diagnosis 

Sometimes urine blockage is not apparent 

until the child develops the symptoms of a 

urinary tract infection. These symptoms 

include 

•	 fever 

•	 irritability 

•	 poor appetite 

•	 vomiting 

•	 unusual smelling urine 

•	 dark urine 

If these symptoms persist, the child should 

be seen by a doctor. For any fever in the 

first 2 months of life, the child should be 

seen by a doctor immediately. The doctor 

will ask for a urine sample to test for 

bacteria. The doctor may also recommend 

imaging tests including ultrasound, VCUG, 

or nuclear scan. 

5	 Urine Blockage in Newborns 
Treatment 

Treatment for urine blockage depends on 

the cause and severity of the blockage. 

Hydronephrosis discovered before the baby 

is born will rarely require immediate action, 

especially if it is only on one side. Often 

the condition goes away without any treatment before birth or sometimes after. The 

doctor will keep track of the condition with 

frequent ultrasounds. With few exceptions, 

treatment can wait until the baby is born. 

Prenatal Shunt 

If the urine blockage threatens the life of 

the unborn baby, the doctor may recommend a procedure to insert a small tube, 

called a shunt, into the baby’s bladder to 

release urine into the amniotic sac. The 

placement of the shunt is similar to an 

amniocentesis, in that a needle is inserted 

through the mother’s abdomen. Ultrasound guides the placing of the shunt. This 

fetal surgery carries many risks, so it is performed only in special circumstances, such 

as when the amniotic fluid is absent and the 

baby’s lungs aren’t developing or when the 

kidneys are very severely damaged. 

Antibiotics 

Antibiotics are medicines that kill bacteria. 

A newborn with possible urine blockage or 

VUR may be given antibiotics to prevent 

urinary tract infections from developing 

until the urinary defect corrects itself or is 

surgically corrected. 

Surgery 

If the urinary defect doesn’t correct itself 

and the child continues to have urine blockage, surgery may be needed. The decision 

to operate depends upon the degree of 

blockage. The surgeon will remove the 

obstruction to restore urine flow. A small 

tube, called a stent, may be placed in the 

ureter or urethra to keep it open temporarily while healing occurs. 

Intermittent Catheterization 

If the child has urine retention because of 

nerve disease, the condition may be treated 

with intermittent catheterization. The parent, and later the child, will be taught to 

drain the bladder by inserting a thin tube, 

called a catheter, through the urethra to 

the bladder. Emptying the bladder in this 

way helps prevent kidney damage, overflow 

incontinence, and urinary tract infections. 

6 Urine Blockage in Newborns 
Hope Through Research 

Researchers from universities and government agencies are working to understand 

the causes of urinary birth defects and to 

find more effective treatments. Through its 

Pediatric Urology Program, the National 

Institute of Diabetes and Digestive and 

Kidney Diseases funds research into bladder 

and urinary tract development, prenatal 

interventions for urinary tract disorders, 

and bladder abnormalities associated with 

spina bifida. Additionally, the National 

Institute of Child Health and Human 

Development has established the Birth 

Defects Initiative to study the genetic 

and molecular mechanisms underlying 

developmental processes of the fetus. 

For More Information 

American Urological Association, Inc. 

1000 Corporate Boulevard 

Linthicum, MD 21090 

Phone: 1–866–RING–AUA (746–4282) 

or 410–689–3700 

Email: aua@auanet.org 

Internet: www.urologyhealth.org 

March of Dimes 

1275 Mamaroneck Avenue 

White Plains, NY 10605 

Email: askus@marchofdimes.com 

Internet: www.marchofdimes.com 

National Institute of Child Health and 

Human Development 

Information Resource Center 

P.O. Box 3006 

Rockville, MD 20847 

Phone: 1–800–370–2943 

Email: nichdinformationresourcecenter@ 

mail.nih.gov 

Internet: www.nichd.nih.gov 

7 Urine Blockage in Newborns 
National Kidney and 

Urologic Diseases 

Information Clearinghouse 

3 Information Way 

Bethesda, MD 20892–3580 

Phone: 1–800–891–5390 

Fax: 703–738–4929 

Email: nkudic@info.niddk.nih.gov 

Internet: www.kidney.niddk.nih.gov 

The National Kidney and Urologic Diseases 

Information Clearinghouse (NKUDIC) is a 

service of the National Institute of Diabetes 

and Digestive and Kidney Diseases (NIDDK). 

The NIDDK is part of the National Institutes 

of Health under the U.S. Department of Health 

and Human Services. Established in 1987, 

the Clearinghouse provides information about 

diseases of the kidneys and urologic system to 

people with kidney and urologic disorders and 

to their families, health care professionals, and 

the public. The NKUDIC answers inquiries, 

develops and distributes publications, and 

works closely with professional and patient 

organizations and Government agencies to 

coordinate resources about kidney and 

urologic diseases. 

Publications produced by the Clearinghouse are 

carefully reviewed by both NIDDK scientists 

and outside experts. This publication was 

reviewed by Robert Chevalier, M.D., University 

of Virginia School of Medicine, and Craig 

Peters, M.D., Harvard Medical School. 

This publication is not copyrighted. The 

Clearinghouse encourages users of this fact 

sheet to duplicate and distribute as many 

copies as desired. 

This fact sheet is also available at 

www.kidney.niddk.nih.gov. 

U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES 

National Institutes of Health 

NIH Publication No. 06–5630 

February 2006