Ulcers are holes in the lining of the upper part of the gastrointestinal tract. When in the stomach, they are called gastric ulcers, when they appear in the duodenum, they are referred to as duodenal ulcers. Duodenal ulcers mainly occur in people between 20 and 50 years of age and gastric ulcers typically appear in people over 40 years of age. Without proper treatment, ulcers can continue to grow and become very painful. Ulcers may also bleed and sometimes there is a need of surgery to repair the damage.