The contrast agent used in ultrasound is a microbubble contrast agent, and the contrast agent is usually expelled from the body in about 30 minutes by breathing through the lungs, with minimal side effects. Since the introduction of ultrasonography, nearly 2,000 patients have undergone ultrasonography every year, and there have not been any cases of allergy to ultrasonography contrast agent, but other side effects have been reported at home and abroad. The main side effects include headache, nausea, pain at the injection site and abnormal sensation, etc. The incidence is also very low about 1%-5%. These adverse reactions are temporary, mild and do not require special treatment, and usually have no sequelae after they subside.