Pelvic effusion 55×29mm is generally more serious, considering pathological pelvic effusion, which may be caused by pelvic inflammatory disease, ectopic pregnancy, rupture of corpus luteum, pelvic peritoneal tuberculosis, malignant tumors of pelvic cavity or abdominal cavity and so on. 1. Pelvic inflammatory disease: pelvic inflammatory disease will lead to the appearance of some plasma, these plasma can not be absorbed by the body will spread to the pelvic cavity to form effusion, if the pelvic effusion has reached 55 × 29mm, indicating that the pelvic inflammatory disease has been more serious. 2. Ectopic pregnancy: most of the ectopic pregnancy is tubal pregnancy, once ruptured, the blood will cause pelvic effusion, which is a more dangerous situation. 3. Rupture of the corpus luteum: Rupture of the corpus luteum may also cause accumulation of blood and pelvic effusion, which can be accompanied by severe lower abdominal pain and other conditions. 4. Pelvic peritoneal tuberculosis: this is caused by Mycobacterium tuberculosis infection, which will exude some plasma fluid and accumulate in the pelvis. 5. Pelvic or abdominal malignant tumor: the tumor can cause pelvic effusion by compressing blood vessels and lymphatic vessels, and ovarian cancer can also cause ascites and pelvic effusion. To sum up, pelvic effusion 55×29mm is more serious, it is recommended to go to the hospital for detailed examination, and under the guidance of professional doctors to treat the symptoms according to the causes, so as not to delay the condition.