The way the organs form in a baby during pregnancy is very complicated. Certain steps must occur in a finely timed order. Most often, if there is one defect in an organ, there will also be other defects. Only rarely does epispadias occur alone. There will also often be issues with the bladder. In rare cases, there can also be defects in the large intestine.
How the epispadias affects the genitals varies. In some boys, it can be just a small dimple on the tip of the penis above the normal urethral opening. With girls, it could be a double clitoris. If the urethra or bladder is involved, the epispadias is usually more severe. This large range of issues is called the exstrophy-epispadias complex (see section on Exstrophy).