If the patient has a vague pain under the left rib cage after inspiration, the possible causes are as follows: firstly, it may be caused by muscle spasm, for example, if the patient is cold or has a poor posture, such as prolonged hunching, it may cause muscle spasm here. Secondly, it may be caused by an old injury, such as an old rib fracture, which may occur when it rains on a cloudy day.