The left side of the lower rib cage pain is usually due to the left side of the lower chest wall rib cage area ribs and neuromuscular tissues because of trauma or inflammatory lesions, or the left quarter of the rib cage area organ lesions and so on, resulting in pressure on the lesion site caused by the pain. 1. Trauma or inflammatory lesions of the ribs and neuromuscular tissues in the ribcage area of the left lower chest wall. (1) Left lower chest wall rib fractures, rib tumors and other lesions when pressed can cause changes in rib periosteal muscle tone, causing pain when pressed below the left rib. (2) When intercostal neuritis in the left lower chest or costochondritis at the left rib arch, pressing and pulling the extraperiosteal nerves and connective tissues of the rib cage can cause pressing pain below the left rib cage. 2. Organic lesions in the left quarter rib area (1) Left upper abdominal organ lesions: pain caused by gastritis, gastric ulcer, splenomegaly, and inflammation or tumor in the tail of the pancreas can involve the left lower chest, and pressing the left lower rib cage will cause obvious pain. (2) Left posterior peritoneal cavity organ lesions: left nephritis, left hydronephrosis and other diseases can also cause significant pain by pressing the left side below the ribs in the kidney area. Pain under the left side of the rib cage by pressing, it is recommended to go to the hospital for further diagnosis and treatment.