If the patient vomits while having back pain, it may be related to the following reasons: 1. It may be caused by too severe pain. There are many diseases, such as herniated lumbar discs or acute lumbar sprains, that may cause severe pain in the lower back. If this happens, it may cause spasm of the gastrointestinal tract, which may then be complicated by vomiting. 2. There may be digestive system-related diseases. In the case of acute pancreatitis, it is possible to have back pain and vomiting at the same time. 3. It may be caused by a neurological infection. In the presence of cerebrospinal meningitis or other types of infections, there may be lumbar pain at the same time, and due to the increase in cerebrospinal fluid pressure, resulting in increased intracranial pressure, followed by jet vomiting. 4. There may be kidney-related diseases. When chronic kidney disease reaches a certain level, or when there is an acute attack, there may be simultaneous lumbar pain and vomiting.