Hydronephrosis is a condition that is sometimes diagnosed in infants prior to or just after birth wherein a backup of urine in the kidneys causes one or both to noticeably swell. Often, the condition disappears by the time a child is born or soon thereafter. Kidney function is usually unaffected in children who experience even moderate forms of the disease, particularly when it resolves itself. That said, it is important to seek medical evaluation for this condition to avoid any possible long-term kidney damage. Treatment for hydronephrosis may include antibiotics, endoscopic surgery, or the insertion of a nephrostomy tube or ureteral stent.