It is manifested by blood vomiting or black discoloration of the stool, the so-called tar stool, and occurs in up to 20% of all ulcer patients. Also highest life-threatening danger exists if the ulcer breaks through into the free abdominal cavity. Such a perforation, in about 5% of all ulcer patients, suddenly leads to severe permanent pain and irritation of the peritoneum. Here, the patient usually indicates a dull permanent pain with radiation in the back. All three complications require surgical treatment, which must be performed immediately, especially in the case of severe bleeding or perforation.