The fallopian tube is a complex organ 12 to 15cm long. The inside of the tube is covered with tiny hairs (called ‘cilia’) which can only be seen clearly with a high power microscope. Once fertilisation of an egg by sperm occurs these ‘waft’ the egg and sperm in the correct direction in to the cavity of the womb.
The ‘proximal’ portion of the fallopian tube refers to the portion of the tube which is next to the uterus. Proximal disease can cause either a complete blockage of the tube (obstructive) or damage leaving only a small opening (non-obstructive). Disease in this part of the fallopian tube is found in 10 to 25% of women with tubal related infertility.
The most common cause of this disease is a condition called salpingitis isthmica nodosa (SIN). The exact cause of this disease is unknown, but the majority of patients with SIN will have been pregnant in the past which leads experts to believe it may be an inflammatory condition related to any pregnancy.
Other causes of proximal tubal disease can include adenomyosis and large polyps (cornual polyps) within the fallopian tube itself. If the disease is only mild, and the sperm manages to be transported to the egg and fertilisation occurs, there is a significantly higher chance of an ectopic pregnancy because the fertilised egg cannot get back into the uterine cavity due to the narrowing of the tube.
The most common site of a fallopian tube blockage is next to the ovary at what is known as the ‘distal’ end. Here there are delicate microscopic fingers called the ‘fimbria’ which normally envelope the ovary at the time of ovulation and pick up the egg to start its journey along the fallopian tube.
Disease of the distal tube can be caused by any pelvic inflammatory condition including infection, endometriosis, appendicitis and previous pelvic surgery. A blockage at this distal end can result in a fluid collection in the fallopian tube known as a hydrosalpinx. The fluid can pass back into the uterine cavity and affect the success rates of assisted conception. A hydrosalpinx can be diagnosed as a result of an X-ray investigation (called a hysterosalpingogram or HSG) or laparoscopy, and occasionally if it is large enough it can be seen under transvaginal ultrasound.
Hydrosalpinges and IVF
Hydrosalpinges can dramatically lower the chance of IVF working, even though the embryos are put back into the uterine cavity. This is thought to be due to the fluid in these hydrosalpinges entering the uterine cavity and damaging the embryos (so that the fluid is said to be ‘embryotoxic’). It may also have an effect of ‘washing away’ the embryo from its implantation site.