What is a horseshoe kidney? Horseshoe kidney occurs in about 1 in 500 children. It occurs during fetal development as the kidneys move into their normal position from the pelvis to the flank area (area around the side, just above the waist). As the kidneys of the fetus rise from the pelvic area, they fuse together at the lower end or base. By fusing, they form a "U" shape, which gives it the name "horseshoe." A horseshoe kidney consists of two normal functioning kidneys attached by a band of tissue called the isthmus. Signs and symptomsEven though a horseshoe kidney is congenital (present at birth), one-third of children will have no symptoms and the condition often goes undetected. In patients who do have symptoms, horseshoe kidney is often diagnosed as the result of an infection, an obstruction or a kidney stone. Testing and diagnosisSince prenatal ultrasound is now a part of the routine care during pregnancy, many renal abnormalities are discovered before the baby is even born. Other horseshoe kidneys may be uncovered during an X-ray or ultrasound for a different reason. As long as your child’s ultrasound is normal and he is not experiencing any symptoms, treatment may not be necessary. Your doctor will recommend the most appropriate course of treatment for your child. If your child has unexplained abdominal pain or flank pain, unexplained nausea, vomiting or hematuria (bloody urine), we will reassess the kidney with an ultrasound. Reviewed by: Division of UrologyDate: May 2011