What causes fluid accumulation?

Pelvic effusion is a very common clinical finding, typically caused by factors such as uterine bleeding, endometritis, intrauterine adhesions, or genital tract malformations. Therefore, pelvic effusion is often associated with uterine inflammation and can be evaluated via hysteroscopy. Additionally, many women develop pelvic effusion postpartum due to pelvic floor relaxation, which impairs the expulsion of residual tissue; in such cases, surgical drainage of the effusion may be required.

What Causes Effusion?

1. Uterine Bleeding

Dysfunctional uterine bleeding (DUB), also known simply as functional uterine bleeding or “menometrorrhagia,” results from neuroendocrine imbalances—not from pregnancy, endometrial tumors, infection, or hematologic disorders. It commonly occurs during adolescence and is invariably anovulatory in nature, thus termed adolescent dysfunctional uterine bleeding.

2. Endometritis

Endometritis refers to inflammatory changes in the endometrial structure caused by various etiologies. The uterine cavity normally provides favorable drainage and undergoes cyclical endometrial shedding, making it uncommon for inflammation to persist chronically within the endometrium. However, if acute endometritis is inadequately treated or if persistent infectious foci remain, recurrent episodes may occur.

3. Cervical Canal Adhesions or Obstruction

Cervical canal adhesions refer to scarring and subsequent narrowing or complete occlusion of the cervical canal, usually resulting from mechanical injury to the cervical mucosa.

4. Genital Tract Malformations

Uterine effusion may present clinically with lower abdominal heaviness or dull pain, increased vaginal discharge, and blood-tinged secretions. In clinical practice, most cases of pelvic effusion in women stem from inflammatory processes—specifically, inflammatory exudates accumulating within the pelvis. Such effusions may develop following endometrial inflammation, wherein slightly viscous fluid leaks from swollen endometrial cells and becomes encapsulated by surrounding tissues, gradually forming a cystic mass. Once uterine effusion is confirmed, pharmacologic treatment may be initiated; however, without timely intervention, medical therapy alone is often insufficient for resolution, and surgical management may become necessary.

The above outlines the primary causes of effusion. We hope this information is helpful to you.