KIDNEY ENLARGEMENT (Hydronephrosis)

Definition: Swelling of the kidney as a result of obstruction to the flow of urine.

1. What caused this condition?

Hydronephrosis in most babies is a minor condition that goes away on its own. It likely represents increased urine production by the fetus prior to delivery that goes away with time. Occasionally, hydronephrosis may be due to an obstruction that is caused by abnormal development of the ureter (the tube that carries the urine from the kidney to the bladder). Hydronephrosis may also represent the backwash of urine from the bladder to the kidney known as vesicoureteral reflux.

2. What tests are needed to further define the disorder?

In most cases, ultrasound imaging is used to discover kidneys that are hydronephrotic. Once a kidney has been determined to be hydronephrotic, depending on the age and gender of the baby, a bladder X ray should be performed to look for backwash of urine up to the kidney (vesicoureteral reflux) or blockage in the urethra if the child is male. In other instances where the condition is quite severe, a nuclear medi- cine renal scan should be performed to rule out obstruction of the kidney. An obstruction might require surgical intervention to preserve the kidney. If the hydronephrosis involves both kidneys, then further evaluation with a standard blood test should be performed in the hospital or office to make sure that kidney function is normal.

3. Is this condition causing my baby any pain or discomfort?

If the kidney is significantly swollen (dilated) or it is obstructed, the baby may have pain, nausea or vomiting, or even blood in the urine. However, most degrees of hydronephrosis do not cause any pain or discomfort.

4. Is it correctable, and will surgery be necessary?

Most hydronephrosis is minor and will resolve or improve on its own as the baby gets bigger. However, if the dilation is significant or severe, then this may represent an obstruction of the kidney that will require surgery to resolve the obstruction. If the dilation of the kidney is related to vesicoureteral reflux, and if the reflux does not resolve as the baby gets older, then correction of the reflux may be necessary. Blockage of the male urethra must be corrected with surgery.

5. Will it predispose my baby to kidney disease or infection in the future?

Most hydronephrosis does not predispose the kidney to disease or infection; however, if the dilation is related to vesicoureteral reflux, reflux is a risk factor for developing both bladder and kidney infections. If the dilation is severe and involves both kidneys, then kidney disease is a possibility.

6. Do we need to consult a urologist and, if so, when?

Once the diagnosis of hydronephrosis is made, the urologist should be consulted to review the X rays, perform a complete history and physical examination of the baby and then determine if any other further studies are necessary. While this is generally not an urgent condition, if the child is having pain, significant infections, or it involves both kidneys, then the urologist should see the child immediately.

7. How will the condition be monitored following discharge from the hospital, and what tests will need to be done?

An ultrasound and further studies are usually recommended approximately four to six weeks following discharge. Depending on whether or not the hydronephrosis is severe, a renal scan may need to be performed. If the hydronephrosis involves both kidneys, then a stan- dard blood test would need to be performed to determine kidney function. If the child has not had an evaluation for vesicoureteral reflux, then a bladder X ray test would be necessary.

8. What danger signs should we look for after leaving the hospital that would indicate that the kidney problem might be getting worse?

The most common symptoms associated with severe hydronephrosis or an obstructed kidney is abdominal, side, or back pain and vomiting. Fever may represent a urinary infection.

9. After discharge from the hospital, when do you wish to see my baby again?

After the child is discharged, we will normally see the child back in our office for an ultrasound and further studies approximately four to six weeks later. See question #7 for details. 

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