Barium sulfate is a poorly soluble to insoluble sulfate salt derived from the alkaline earth metal barium. In natural stocks, it occurs as barite. As a powder, barium sulfate glows white in color. It is used as a filler in plastics for the production of paints and medically as an X-ray positive contrast agent.
What is barium sulfate?
Barium sulfate is a sparingly soluble to insoluble sulfate salt derived from the alkaline earth metal barium. In natural stocks, it occurs as barite. Barium sulfate is a substance with a high impermeability. Therefore, it is used in radiology as a sparingly soluble suspension in the form of X-ray positive contrast media. It is not absorbed and is suitable for imaging the digestive tract. Subsequently, the agent is excreted unchanged as white stool. Administered as an esophageal gavage, barium sulfate is used to obtain physiologic information. It enters the stomach in oral form through the esophagus and is then excreted through the digestive tract. Another option is rectal introduction for obtaining morphologic information.
Pharmacologic action
Barium sulfate suspensions used in X-ray diagnostics vary in viscosity, particle size, and concentration. In addition to barium sulfate, isotonizing agents such as sorbitol and thickening and dispersing agents are used to prevent flocculation (flocculation). The contrast agent is often used in combination with methyl cellulose gels and carbon dioxide to induce distension of the gastrointestinal tract by introducing air. This simultaneous use of two agents is called the double contrast method. In this way, better visualization of the intestinal mucosa in relief is achieved, as the contrast agent alone only results in a thin coating on the surface of the intestine. Contrast agents are used to visualize organs with X-ray examinations that have only a slight difference in density from the surrounding organ systems and tissues. In this way, physicians are able to distinguish pathological processes and healthy tissue. Since barium sulfate suspensions are not soluble in water and fat, they are not absorbed by the body and are excreted unchanged. The toxic effect of the starting material barium metal is very low.
Medical application and use
Contrast agents can have undesirable side effects that manifest in various organs and the skin. If X-ray examination using contrast media is indicated, there are generally stricter requirements than for therapeutic administration of drugs. Modern X-ray contrast media undergo many years of tolerability studies before they are approved by the legislature. Doctors are also obliged to inform their patients about the possible risks. By using contrast agents, physicians gain additional information that they would not obtain without imaging and using these agents. The additional information is divided into two categories: morphological (structural) and physiological (functional). A typical examination for the former is double-contrast imaging of the colon by rectal instillation (dropwise administration) of a barium suspension. Subsequent introduction of air into the bowel reveals the bowel lumen (clear width) by filling and negative contrast. This results from the high permeability of the air to X-rays. Morphologic changes such as polyps, strictures, inflammation, and outpouchings become visible. Functional information is obtained by giving a pap smear. In this way, physicians can detect mobility disorders of the esophagus. Due to the high white luminosity, the examined organ or tissue can be clearly distinguished from the surrounding organ and tissue structures, which remain dark on the X-ray image. Patients must be fasting for the examination, which means they must not eat or drink anything for several hours beforehand. In most cases, this contrast imaging is performed in the morning, when the patient has not yet had breakfast, so that he or she only has to abstain from food intake for a short time.
Risks and side effects
The treating physician must perform a careful risk-benefit assessment before using this radiographic contrast agent, as serious foreign body reactions may occur if the barium sulfate suspension is delivered to the wrong site. Its use is contraindicated if there is a perforation in the area of the stomach and intestines and there is a risk of aspiration (ingestion) of the contrast medium. This is the case, for example, with fistulas or a perforated ulcer in the form of a deep-seated substance defect. In the case of this faulty administration, the contrast medium enters the peritoneal organs, for example, the liver, spleen, stomach, colon, uterus or ovaries. If barium sulfate gets into the free abdominal cavity, life-threatening complications can occur. In the case of an irrigoscopy (colon x-ray), an x-ray examination should not be performed until 14 days after the biopsy has been performed. Intraperitoneal administration that is not indicated may result in patient death. The opposite of “peritoneal” is “retroperitoneal.” Primarily retroperitoneal are all organs located behind the abdominal cavity, such as the ureters and kidneys. Secondary retroperitoneal are the organs that are connected to the dorsal abdominal wall. These organs include duodenum (small intestine attached to the stomach), pancreas, and ascending and descending colon. Less dangerous and rather rare side effects include constipation, sweating, weakness, stomach cramps, itching, hives, or redness of the skin. Difficulty breathing or swallowing, hoarseness, and temporary confusion are also possible.
