Diverticulitis, angina and gastritis are three diseases that cause left side pain on a human body, according to Mayo Clinic. Many conditions that cause left side pain are not serious, such as gas pains or pulled muscles, while others need to be treated as soon as possible.
Diverticulitis occurs when the diverticula in the inner wall of the intestines become infected, notes MedlinePlus. Doctors do not know what causes diverticula to form on the intestinal lining, yet it occurs in most older Americans. It is thought that a low-fiber diet may be the cause of this condition because it leads to constipation and strain, which may be factors to its development. Patients with diverticulitis have severe and sudden symptoms including tenderness in the lower left side of the abdomen, bloating, loss of appetite and nausea.
Angina occurs when there is an inadequate amount of blood reaching the heart muscle, explains the American Heart Association. Patients suffering from angina experience chest pain that feels like pressure in the chest, which can extend into the arms, neck, back and other parts of the body. There are many types of angina, and the condition is typically due to a blockage or narrowing of an artery.
Gastritis occurs when the stomach lining becomes inflamed, leading to poor digestion, according to the National Institute of Diabetes and Digestive and Kidney Diseases. The condition can be either chronic or acute, and chronic gastritis lasts for years if not treated. Gastritis commonly occurs as a result of a Helicobacter pylori infection, an autoimmune disease or damage to the stomach lining. Many patients with gastritis do not have any symptoms, while others experience upper abdominal pain, nausea and vomiting.