A vague pain inside the left lower rib cage is a hidden pain superficially or deeply in the left lower rib cage or slightly upward. The cause of this pain may be the respiratory muscle spasm caused by strenuous exercise, which is often referred to as forked breath, and can generally be recovered after rest; some diseases of the tissue structures or organs near this location can also cause pain, such as costochondritis, spinal chest pain, left lower pneumonia, pleurisy, etc.: 1. Costochondritis: the strain of heavy work, trauma and other reasons may lead to the formation of acute damage to the rib cartilage, which can be manifested as The pain is obvious when pressed hard, and will increase with coughing or exertion; 2. Spinal chest pain: the common cause is herniated discs or osteophytes caused by misalignment of the thoracic spine, which can directly compress or indirectly affect the nerves causing hidden pain under the left ribs, often accompanied by pressure and involvement pain; 3. Left lower pneumonia: usually caused by pathogenic microorganisms triggering inflammation of the left lower lung, part of which is infectious. It is accompanied by symptoms of fever and cough, and some people will have symptoms of hidden pain under the left ribs, and the pain will increase when coughing; 4. Pleurisy: It is an inflammation in the pleural cavity, and the inflammation on the left side is manifested as hidden pain under the left ribs, often accompanied by symptoms of cough, fever and difficulty in breathing. Coughing will aggravate the pain, and pressing hard or holding the breath will reduce the painful condition; some pleurisy can be caused by malignant tumors; 5. Other: intercostal neuralgia may appear as hidden pain in a small number of people, and some gastrointestinal diseases may cause hidden pain under the left rib cage. Cardiovascular diseases may cause hidden pain below the left rib cage, which is commonly accompanied by chest tightness and accelerated heart rate. The specific disease should be diagnosed by going to the hospital for relevant examination and follow the medical advice for relevant treatment, not to blindly take painkillers, etc., which may delay the condition and cause other complications due to delayed treatment.