Causes of pericardial effusion include infectious and non-infectious factors; laboratory tests, electrocardiogram, and imaging tests are usually required when pericardial effusion is suspected. 1. Causes (1) Infectious factors. Pericardial effusion can be caused by infections caused by viruses, bacteria, fungi, protozoa, etc., such as colds, pneumonia, tuberculosis, skin abscesses, and intestinal amoebic dysentery. (2) Non-infectious factors. Including a variety of tumors, such as lung cancer, breast cancer, lymphoma, etc.; rheumatic diseases, such as systemic lupus erythematosus, rheumatoid arthritis; cardiac or vascular injuries, heart failure, hypothyroidism, uremia, chest radiation therapy, etc.. 2.Examination (1) Laboratory tests. Including routine tests such as blood and urine routine, liver and kidney function, coagulation function, blood glucose, etc.; specific tests such as tumor marker test and rheumatic disease-related antibody measurement. These tests can understand the basic condition of the organism, determine the existence of other diseases, and further clarify the cause of the disease. (2) Electrocardiography. It has a certain auxiliary diagnostic value and can also exclude other heart diseases. (3) Imaging examination. Including chest X-ray examination, which can show a “flask-like” image; ultrasound electrodynamic examination, which is usually preferred and can clarify the diagnosis of the disease; cardiac CT, MRI examination and so on. (4) Diagnostic pericardiocentesis fluid test. It can determine the nature of fluid accumulation. It is recommended that the relevant people clarify the cause and diagnosis of the disease after timely consultation, and carry out regular treatment.