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Brian A. Roelof, M.D. The primary function of the kidney is to filter waste products from the blood. The waste products are passed out of the kidney as urine. The urine collects in the renal pelvis and then passes through the ureteropelvic junction and into the ureter. It passes from the ureter into the bladder and then is eventually passed out through the urethra. The junction where the ureter joins the renal pelvis (ureteropelvic junction - UPJ), can sometimes be partially blocked. This blockage may be minimally mild, moderate, or quite severe. If the congenital blockage is moderate or severe, it will restrict the flow of urine from entering the ureter. This creates a back pressure which expands the size of the renal pelvis (hydronephrosis) and begins to injure the renal parenchyma (meaty part of the kidney). This may eventually destroy the kidney, cause infections or stones or high blood pressure because of the stagnant urine. Bleeding and kidney injury after minor trauma may also occur. The obstruction may be on one side or involve both kidneys (bilateral). Symptoms of Ureteropelvic Junction (UPJ) Obstruction Fetal ultrasounds are being done on many pregnant women. Often times, an abnormal fetal kidney can be detected (1 : 500 to 1 : 1000 fetuses). If so, the obstetrician and pediatrician are alerted to this fact. Sometimes we are consulted prior to the birth of the child and other times we are consulted after the birth of the child. If obstruction is only on one side, the unborn child will probably not have any particular signs or symptoms. If the unborn child has obstruction on both sides, there may be an insufficient amount of amniotic fluid in the uterus (oligohydramnios). Occasionally, a newborn infant is noted to have a mass in his abdomen and this leads to the investigation and discovery of a blockage of a kidney. In older children, the presenting signs and symptoms may be that of fever and urinary tract infections or blood in the urine particularly after minor injury. Causes The blockage is usually caused by a congenital narrowing of the junction where the ureter meets the renal pelvis. It might also by caused by kinking secondary to a fibrous band or secondary to a crossing blood vessel. Another case is that the ureter may enter the renal pelvis in an abnormal location. Work-up for a UPJ Obstruction A kidney ultrasound test is a very common test used to determine if there is an obstruction with resulting back pressure (hydronephrosis). The ultrasound can tell us whether there has been a thinning of the meaty portion (parenchyma) of the kidney. We may also obtain a kidney x-ray. The kidney x-ray (intravenous pyelogram) is a series of kidney x-rays following the intravenous injection of a dye (contrast material). This test not only shows the anatomy, but also tells us something about the physiology and function of the kidney. Many children will have a bladder x-ray (VCU). A catheter is passed trough the urethra into the bladder and contrast material is instilled to determine if urine goes from the bladder backwards to the kidney. If so, this can mimic the obstruction when no real obstruction is present or it might worsen an obstruction if an obstruction is present (vesicoureteral reflux). A diuretic nuclear renal scan is also commonly used. This test can tell us how well the involved kidney is functioning in comparison to the other kidney. We give the diuretic (usually Lasix) to determine how quickly the kidney pelvis can pass the urine through. If there is a significant blockage, the excretion of urine is slowed on the test. Surgical Correction of UPJ Obstruction Not all UPJ obstructions require surgical correction. Many can be followed conservatively and corrected only if they are becoming worse. The correction of a UPJ obstruction is a surgical procedure called a pyeloplasty. This involves a general anesthetic and an abdominal or flank side incision. The area of the obstruction is found and a decision is then made as to how to correct the problem. Usually the obstructed portion is removed and the ureter is sewn back on to the renal pelvis in a special way to allow a nice funneled shape and easy flow of urine from the renal pelvis into the ureter. This procedure is usually highly successful. A small rubber drain is left in the area of the operation so that any urine leakage can drain to the outside of the body. The rubber tube is left in for several days. Occasionally, a tube is left in the kidney itself for drainage and this might even be in for several weeks (nephrostomy tube). Complications Complications of the operation (pyeloplasty) can include bleeding and infection. Excessive bleeding may occur with any operation, but it is unusual to have to transfuse the children. Infection is possible as it can occur in any operation. It is also possible to have persistent drainage of the urine to the outside or continued delayed drainage of urine from the kidney into the ureter. A narrowing or scarring may occur and may require a repeat operation. There are other more uncommon potential complications. If a significant obstruction is found in newborn infants, we may correct the obstruction in the first few months of life. We feel this gives the kidney a better chance to develop its full potential. Surgery on young infants seems to be quite safe when done in a hospital such as DeVos Children's Hospital at Butterworth. Follow-up After a Pyeloplasty A few months after the operation an ultrasound or other test will be performed to determine if the pyeloplasty was successful. If there is any question, further testing may be performed. We feel the children should be followed for several years because of the potential for scarring. The usual follow-up exam is an ultrasound.
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