Back flow of urine from bladder to Kidney

Normally, urine flows from the kidneys, down through tubes known as ureters, to the bladder. The ureters enter the bladder in such a way that urine can enter the bladder, but it can't back up from the bladder into the ureters.
Vesicoureteral reflux (VUR) is an abnormal movement of urine from the bladder into ureters or kidneys. Urine normally travels from the kidneys via the ureters to the bladder. In vesicoureteral reflux the direction of urine flow is reversed (retrograde).
In vesicoureteral reflux (VUR), the ureter doesn't grow long enough during prenatal development and it enters the bladder abnormally. As a result, urine can back up, or reflux, from the bladder into one or both ureters and, in severe cases, up into the kidneys.
The condition may improve or disappear as the child gets older and the ureters grow longer.
Vesicoureteral reflux may present before birth as prenatal hydronephrosis, an abnormal widening of the ureter or with a urinary tract infection or acute pyelonephritis.
Symptoms such as painful urination or renal colic/flank pain are not symptoms associated with vesicoureteral reflux.
Newborns may be lethargic with faltering growth, while infants and young children typically present with pyrexia, dysuria, frequent urination, malodorous urine and GIT symptoms, but only when urinary tract infection is present as the initial presentation of VUR.

VUR can also be caused by reasons not related to anatomy, such as voiding problems or problems with nerve tissue in the bladder. Children with this kind of VUR may be given different treatment.
The term prenatal hydronephrosis refers to dilation of the renal collecting system. The collecting system is the structure that collects urine directly from the kidney tissue and routes it by way of the ureter to the bladder. Hydronephrosis is also known as "swelling of the kidney". Routine use of maternal ultrasound has become more prevalent during the past decade allowing for urologists and pediatricians alike to be informed of possible kidney defects before birth.
In the United States, 3 million maternal ultrasounds are performed annually with hydronephrosis being the most commonly detected anomaly. It is detected in as many as 42,000 fetuses (1.4%). Thus obstetricians and pediatric urologists alike commonly encounter the diagnosis of prenatal hydronephrosis.
With the use of sonography, dilation of the renal collecting system can be observed, but obstruction can not be confirmed. However, up to one half of these neonates do not have hydronephrosis on the postnatal ultrasound. The remaining one half with hydronephrosis have a range of diagnoses. The majority (64%) are attributed to ureteropelvic junction (UPJ) obstruction. The remaining 36% are secondary to vesicoureteral reflux, megaureter, or posterior urethral valves. UPJ obstruction refers to a kink or stricture of the collecting system as it begins to leave the kidney to form the ureter. This causes blockage of urine flow and can possibly lead to infections, scarring, and long term damage of the kidney. Reflux is another important condition that is described elsewhere in our web site. In short, this refers to a condition that allows for the backflow or reflux of urine up into the kidney from the bladder. If the urine is infected with bacteria, this can also lead to infection, scarring, and damage to the kidneys.
Prenatal imaging
Despite widespread use of ultrasound, a debate exists in the field of maternal fetal medicine over the required use of gestational (in utero) ultrasound. Clear indications for sonography include discrepancies in fundal height for gestational age, elevated levels of maternal serum alpha fetal protein, and a history of previous pregnancies resulting in congenital anomalies. Regardless of the controversy, when a gestational ultrasound is performed certain basic details must be covered in the examination. These include:
  1. Estimation of fetal size and maturity
  2. Amniotic fluid volume
  3. Standard fetal survey of head, spine, heart, lungs, limbs, and abdomen
  4. Assessment of kidneys including position, size, and texture
  5. Appearance of ureters and collecting system
  6. Bladder volume, wall thickness, and emptying
  7. Examination of other pelvic organs
  8. Appearance of external genitalia
Fetal kidneys can be visualized by the 14th to 15th week of gestation. By the 20th week of gestation, the internal architecture of the kidneys can be assessed. A normal fetal ureter is rarely visualized during ultrasonography. The actual incidence of genitourinary abnormalities on prenatal ultrasound is .2%.
Hydronephrosis is the most common abnormality detected on prenatal ultrasonography. It accounts for about 50% of all prenatally detected defects. When prenatal hydronephrosis is discovered on ultrasound, the finding does not confirm the presence of obstruction. This is due to the extremely elastic nature of the fetal kidney.
Vesicoureteral Reflux

It's especially important to promptly diagnose and treat VUR in infants and small children, since without treatment most of them will develop another urinary tract infection. Waiting until a child has had two or more urinary tract infections before having an evaluation increases the risk of permanent kidney damage or scarring.

Vesicoureteral reflux is usually diagnosed in one of two ways. Children who have a urinary tract infection that's been confirmed by a lab test will have an X-ray evaluation called a voiding cystourethrogram. During the test, the bladder is filled with contrast material that shows up on X-rays. If the child has VUR, the contrast material will backflow into the ureter and kidneys.

Alternately, VUR may be suspected when a prenatal ultrasound reveals that the fetus has dilated kidneys. If this occurs, a voiding cystourethogram is done soon after the birth of the baby.
Other tests may include:
Kidney and Bladder Ultrasound — This test is routinely recommended prior to the voiding cystourethrogram. It provides an outline of the kidneys, ureters and bladder, and we use it to look for less common urinary tract defects that can cause urinary tract infections or kidney dilation. The test doesn't require radiation and is painless.

Kidney (Renal) Scan — A kidney scan may be performed if the above tests are abnormal or if your child has repeated, fever-causing infections. A kidney scan shows the actual function and drainage of the kidneys, and it can also reveal if there's kidney damage or scarring from a previous urinary tract infection.

  • Nuclear Cystogram — This test is very similar to the voiding cystourethrogram, but it involves less radiation and is very sensitive for reflux. The voiding cystourethrogram is the preferred test for initially diagnosing reflux, because it provides a clearer picture of the lower urinary tract and therefore can rule out other less common abnormalities, as well as grade the severity of the reflux. Once the diagnosis has been made by the voiding cystourethrogram, the nuclear cystogram is the recommended follow-up test. The nuclear cystogram is also used to screen siblings of children who have reflux to determine if they also have the condition.
Reflux is graded on a scale of one to five, with one being a mild form and five being severe. The degree of reflux is used to make decisions on how to treat the child. More severe grades are less likely to clear up spontaneously and more likely to cause kidney damage if they're not treated.
Vesicoureteral reflux, or VUR, is treated either with medication or surgery, depending on the severity of the reflux, the child's age, the number and severity of urinary tract infections and the amount of kidney damage seen on X-ray studies.
Treatment always includes a low daily dose of antibiotics. These antibiotics are very specific for the urinary tract and have very few side effects. The goal is to prevent kidney infections until the reflux goes away or is corrected. The type of antibiotic we use will depend on your child's age and allergies.

Medical Therapy

Because many cases of reflux resolve on their own as the child grows, medical therapy may be all that's needed. Medical therapy entails using antibiotics to prevent infection until the condition resolves, and monitoring your child to make sure it does resolve.
Children receiving medical therapy will take a small dose of antibiotics every day. An ultrasound and cystogram will be done annually to assess the kidneys and see if the reflux has resolved. If the reflux persists for several years without improvement, surgery may be considered. If your child continues to have fever-causing urinary tract infections despite taking antibiotics, then surgery should be considered. Again, the goal is to prevent scarring or damage from a kidney infection.

Surgical Therapy

Surgery would be performed if your child has more severe reflux, fever-causing urinary tract infections despite being on antibiotics, and signs of kidney damage due to repeated infections. Surgery may also be discussed when, after giving time for the condition to go away as the child grows, repeated voiding cystourethrograms show that the reflux doesn't appear to be improving.
In the surgical procedure, the refluxing ureter is repositioned or re-implanted in the bladder wall. The end of the ureter is surrounded by bladder muscle in this new position in the bladder, which prevents urine from "backing up" or refluxing toward the bladder.
Your child will be in the hospital for three to four days. After the surgery, your child will still need to take antibiotics daily until the bladder and ureter are healed. An ultrasound will be performed about a month after surgery and, depending on the case, a voiding cystourethrogram may be performed six months following surgery.


Younger children are more prone to VUR because of the relative shortness of the submucosal ureters. This susceptibility decreases with age as the length of the ureters increases as the children grow. In children under the age of 1 year with a urinary tract infection, 70% will have VUR. This number decreases to 15% by the age of 12.

International Classification of Vesicoureteral Reflux

  • Grade I – reflux into non-dilated ureter
  • Grade II – reflux into the renal pelvis and calyces without dilatation
  • Grade III – mild/moderate dilatation of the ureter, renal pelvis and calyces with minimal blunting of the fornices
  • Grade IV – dilation of the renal pelvis and calyces with moderate ureteral tortuosity
  • Grade V – gross dilatation of the ureter, pelvis and calyces; ureteral tortuosity; loss of papillary impressions
The younger the age of the patient and the lower the grade at presentation the higher the chance of spontaneous resolution. Most (approx. 85%) of grade I & II cases of VUR will resolve spontaneously. Approximately 50% of grade III cases and a lower percentage of higher grades will also resolve spontaneously.

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