What is Intrauterine Fluid Accumulation?
Intrauterine fluid accumulation refers to fluid seen on ultrasonography within the uterine cavity, known as the endometrial cavity. The fluid may appear as a thin line or may distend the uterine cavity noticeably. It can appear temporarily, particularly during IVF cycles in which the ovaries are stimulated. It is not a diagnosis in itself; the underlying cause needs to be assessed, along with whether the fluid persists up to the day of embryo transfer.
Why does Fluid Accumulate in the Uterus?
Fluid in the uterine cavity can flow in from a damaged, fluid-filled tube connected to the uterus — that is, a hydrosalpinx. Blood or fluid collecting within an isthmocele (uterine tissue at an old caesarean scar that has not healed completely), cervical stenosis, endometritis (inflammation of the uterine lining), intrauterine adhesions, and polyps or fibroids affecting the uterine cavity can also lead to fluid accumulation. Rising hormone levels and increased intrauterine secretions during ovarian stimulation can cause a temporary appearance of fluid in some patients.
What are the Symptoms of Intrauterine Fluid Accumulation?
Many patients have no complaints at all, and the fluid is seen only on ultrasonography. Depending on the underlying cause, pelvic pain, discharge, irregular bleeding, spotting after menstruation, or difficulty becoming pregnant may accompany it. Significant fluid persisting in the uterine cavity at the time of embryo transfer can adversely affect the embryo’s contact with, and implantation in, the endometrium. By contrast, transient fluid seen early in treatment that resolves before transfer may not have the same effect.
How is Intrauterine Fluid Accumulation Diagnosed?
Fluid can be readily seen with transvaginal ultrasonography. The assessment records the amount of fluid, when it appeared, and whether it resolves on follow-up. The tubes are investigated for hydrosalpinx, and possible causes within the uterine cavity such as polyps, fibroids, adhesions, or an isthmocele are looked for. Where necessary, saline infusion sonography (ultrasonography performed with fluid introduced into the uterus), hysterosalpingography (HSG), hysteroscopy, infection testing, or magnetic resonance imaging may be used.
How is Intrauterine Fluid Accumulation Treated?
Treatment is directed at the underlying cause rather than at the fluid itself. Transient, small amounts of fluid can be monitored with ultrasonography. When a hydrosalpinx connected to the uterus is identified, removing the tube or closing off its connection to the uterus before IVF can improve pregnancy outcomes. If a polyp, fibroid, adhesions, isthmocele, cervical stenosis, or infection is present, appropriate treatment is planned. If fluid remains in the uterine cavity on the day of embryo transfer, postponing the transfer and freezing the embryos may be more appropriate for some patients. Because draining the fluid alone may not provide a lasting solution, the decision should take into account the cause of the fluid, its amount, and whether it recurs.
