Pain within the left back needs to be alerted to a variety of conditions, but no specific four exist; pleurisy, pneumonia, cardiac disease and cervical spondylosis, biliary colic radiating pain and a variety of other conditions can generally be considered, and further examination in the hospital is recommended. 1. Pleurisy, pneumonia: if there are pleural adhesions, bacterial as well as tuberculous pleurisy, pneumonia and other respiratory diseases may lead to involved pain in the left back. 2. Heart disease: If there is coronary heart disease, heart attack, myocardial ischemia and other heart diseases that lead to angina pectoris, the angina pectoris can also radiate to the back of the left shoulder, causing pain in that area. 3. Cervical spondylosis: There are many types of cervical spondylosis, and in the case of radicular cervical spondylosis, the protruding nucleus pulposus may compress the nerves in the back of the shoulder, causing pain in the back of the shoulder. 4. Digestive diseases: biliary colic, pancreatic diseases, stomach and duodenal tumors can also cause shoulder and back pain. Therefore, pain inside the left back does need to be alerted to a variety of other diseases and further examination is recommended.