Leucine aminophthaleinase is a protease that can be used as an aid in determining hepatic and biliary disorders as well as normal liver function after a blood test. Clinically, if a patient has high leucine aminopeptidase, it is often considered that the patient has hepatitis cirrhosis or biliary tract tumor disease and extrahepatic tumor disease. For patients with hepatitis and cirrhosis, the leucine aminopeptidase is usually high during the examination, but the degree of elevation is not serious, but if the patient has biliary tract tumor disease or extrahepatic tumor disease, the patient’s leucine aminopeptidase will be obviously elevated, and sometimes up to tens of times and hundreds of times of the situation. In such cases, patients should consider actively improving relevant examinations, such as ultrasound of the upper abdomen and MRI of the upper abdomen, to comprehensively determine the cause of leucine aminopeptidase elevation, whether it is due to hepatitis disease or biliary tract tumor disease.