What is hydronephrosis?

The urinary tract is the body’s drainage system for removing wastes and extra fluid. The kidneys filter out waste and deposit it in urine. Urine flows from the kidneys to the bladder through tubes called ureters. The bladder stores the urine until you go to the bathroom.

In hydronephrosis, one or both kidneys swell because a blockage in the urinary tract causes urine to back up into the kidneys. It also can be caused by a backward leak in the urinary system (reflux), usually caused by muscle weakness.

Hydronephrosis is the most common problem found during ultrasound of a baby in the womb. The swelling of the baby’s kidney may be easy to see or barely detectable. Lots of parents have been told of the condition and that it needs to be monitored. Boys have hydronephrosis more frequently than girls, but girls do get this. If your baby should be diagnosed with this condition, don’t feel guilty – it’s not your fault. There’s nothing a pregnant woman does or doesn’t do that causes this condition.

When hydronephrosis happens to a baby in the womb, it’s called fetal hydronephrosis. In over half of cases it goes away without lasting problems and rarely requires immediate action, especially if it is unilateral, only on one side. The health care provider should keep track of the condition with frequent ultrasounds to see if it goes away or gets worse. Sometimes the blockage can damage the developing kidneys or can, in rare cases, become life-threatening for the baby.

Most babies who need treatment don’t need it until after birth. But if hydronephrosis becomes life-threatening before birth, mom may need to give birth early or have surgery to put a shunt (small tube) into the baby’s bladder while still in the womb. The shunt drains urine into the amniotic fluid until birth. After birth, mild hydronephrosis may go away without treatment. If the blockage doesn’t go away, the baby may need surgery.

A baby with possible urine blockage or reflux may be given low dose antibiotics to prevent urinary tract infections from developing until the defect corrects itself or is corrected with surgery.