The left side below the rib cage mainly includes thoracic organs and left upper abdominal organs. 1. Thoracic organs: The thoracic organs located below the left side of the rib cage mainly include the lungs, heart, and part of the diaphragm. 2. Upper left abdominal organs: The abdominal organs located in this area mainly include the stomach, part of the transverse colon, pancreas, spleen, and so on. If you feel uncomfortable in the left side of the lower ribs, it is possible that the above organs have lesions, which can be clarified by chest X-ray, electrocardiogram, chest CT, abdominal CT, gastroscopy, abdominal ultrasound and other auxiliary means of examination to determine the location of the lesions. If you feel uncomfortable below your left rib cage, it is recommended that you go to a specialist in the hospital and have your doctor analyze your symptoms, signs and symptoms, medical history, and auxiliary tests to determine the cause of the disease before taking appropriate treatment measures.