In the clinic, I met a patient who brought a pile of ultrasound sheets in front of me and asked me to cure her pelvic effusion. I saw that every ultrasound indicated a small pelvic fluid, and the sound transmission was acceptable. The patient was anxious about how the pelvic fluid could not disappear after such a long time of treatment, and insisted that the pelvic fluid indicated inflammation in the pelvis and must be cured. I felt at that time that this patient had been severely brainwashed by which doctor in front of her that pelvic effusion is pelvic inflammatory disease and must be cured, hence this little episode. I gave her an example that didn’t quite match but could be explained at the time: everyone has tears, there are tears when he/she cries, does it necessarily mean that he/she is crying when there are tears? He/she may be laughing, can he/she treat the tears without them? Pelvic effusion is formed by the filtration of peritoneal exudate. Under normal circumstances, a small amount of fluid may exist without treatment, such as during menstruation, ovulation or at any time. Pelvic fluid does not mean pelvic inflammatory disease, nor is it a diagnostic condition for pelvic inflammatory disease. If there is vague pain in the lower abdomen, lumbosacral discomfort, lifting pain in the cervix on gynecological examination, and pressure pain in the uterus or adnexal area, if the ultrasound suggests a small pelvic fluid at this time, pelvic inflammatory disease may be present, but internal bleeding must also be excluded. If the pelvic and abdominal fluid accumulation is high, ascites due to cirrhosis, ascites due to peritoneal tuberculosis, inflammatory exudate due to inflammation of pelvic and abdominal organs such as hepatitis, pancreatitis, appendicitis, etc.; if abdominal pain is severe with shock manifestations and progressive decrease of hemoglobin, internal bleeding due to rupture of pelvic and abdominal organs (rupture of liver, spleen, uterus, fallopian tube pregnancy, ovarian corpus luteum, etc.) should be considered. If necessary, posterior vault aspiration or laparotomy should be performed to extract the fluid for clear diagnosis.