The bulging of an internal organ through a weak area or tear in the muscle or other tissue that holds it in place. Most hernias occur in the abdomen. Hernias may be caused by muscle weakness or straining due to heavy lifting. Hernias can cause extreme pain. Treatment is surgery to remove the hernia. There are several different types of hernias, including: Congenital diaphragmatic hernia-a birth defect that needs surgery. Hiatal hernia-small opening in the diaphragm that allows the upper part of the stomach to move up into the chest. Incisional hernia-due to a scar. Inguinal hernia-This is the the most common type and occurs in the groin. Umbilical hernia-occurs around the belly button.