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Endometrial or uterine polyps are soft, fingerlike growths which develop in the lining of the uterus (the endometrium). They develop because of excessive multiplication of the endometrial cells, and are hormonally dependent , so that they increase in size depending upon the estrogen level. They can usually be detected on an ultrasound scan if this is done mid-cycle, when estrogen levels are maximal, but are easily missed if the scan is not done at the right time of the menstrual cycle. Polyps are an uncommon but important cause of infertility, because they can easily be removed during hysteroscopic surgery.
Fig 1. Uterine polyp as seen during hysteroscopy
Fig 2. Uterine polyp seen during ultrasound scan after infusion of saline which outlines the polyp in the cavity
While the commonest problem found in the uterus is a fibroid (myoma or leiomyoma), this is rarely a cause of infertility, and is usually an incidental finding of little importance. Fibroids are common benign smooth muscle tumors which arise in the wall of the uterus, and may be single or multiple. About 25% of all women over the age of 35 have fibroids.
Most fibroids develop in the wall of the uterus (intramural ) or protrude outside of the uterine wall (subserous fibroids), and these can usually be left alone, since they do not hinder fertility, and neither do they cause problems during the pregnancy. In fact, unnecessary surgery to remove the fibroid often causes more harm than good. This surgery often creates adhesions, which causes the tubes to get blocked.
However, if the fibroids are very large, they may need surgical removal, and this procedure is called a myomectomy. Some doctors give an injection of a GnRH analog prior to surgery in order to shrink the fibroid and make surgery technically easier. When performed by an expert, it is a safe and effective procedure which can be accomplished with minimal blood loss. However, sometimes because of uncontrollable bleeding the surgeon may be forced to remove the entire uterus (a procedure called a hysterectomy), and this is obviously a disaster for the infertile woman!
The standard technique for removing a fibroid is through open surgery (laparotomy). It is now also possible to remove fibroids through the laparoscope, but laparoscopic myomectomy does not allow for optimal reconstruction of the uterus. Submucous fibroids are an important cause of infertility, because they interfere with implantation of the embryo, by acting as a foreign body. These are best removed by an operative hysteroscopy. While surgery can remove the fibroid, it can recur again, and most doctors advise the patient to try to conceive as soon as possible after surgery.
Fig 2. Schematic showing a submucous fibroid; and a subserous fibroid compressing the right fallopian tube
Fibroids may grow larger during the pregnancy, but usually pregnancy and delivery are uneventful. In rare cases, after a myomectomy, uterine rupture may occur during pregnancy or delivery, and this complication may result in severe blood loss, fetal loss and even maternal death.
Because of the potential for catastrophic results, it is recommended that women have cesarean deliveries in the following circumstances: 1) when the myomectomy involved full-thickness incision of the uterine wall or multiple deep uterine incisions or 2) when myomectomy was complicated by infection which may have weakened the uterine wall or 3) when there is doubt regarding the adequacy or extent of the uterine repair.
The uterus was often a neglected organ in the infertility workup, partly because we did not have the tools to study it properly. Hysteroscopy, hysterosalpingography and vaginal ultrasound are all complementary procedures for evaluating the uterine cavity in the infertile woman. The HSG is good for looking for polyps, adhesions and septa which appear as "filling defects" on the X-ray. However, careful radiologic technique is a must. Vaginal ultrasound is excellent for detecting submucosal fibroids or polyps, which can be missed on hysteroscopy and HSG. Of course, the major advantage of hysteroscopy is it offers the chance of treating the problem as well!
We are now also developing newer techniques to study the uterus. One of our major areas of ignorance today is the complex process of embryo implantation. It is obvious that the endometrium has a key role to play in this process, in which the embryo has to appose and attach itself to the maternal endometrium and invade into it. At present, the tools we have to study endometrial function and receptivity are very crude. They include primarily transvaginal ultrasound, to assess the endometrial thickness and texture, but this provides very limited and indirect evidence of endometrial functions. Colour Doppler ultrasound has also been used to assess endometrial blood flow ( perfusion), but its utility is limited.
Since embryo-endometrium interaction is a biochemical process, a lot of study has been done on the role of the molecules involved in this process. Recent research has shown that the normal endometrium contains various cell adhesion proteins called integrins, which allow the embryo to interact with it. Studies have shown that the endometrium of some infertile women is deficient in some of these integrins, and this deficiency may be responsible for failure of the embryo to implant successfully. Thus, testing the endometrium for beta integrin can be a useful marker for uterine receptivity. This test involves doing an endometrial biopsy at a specific point in the menstrual cycle, and evaluating this with special staining techniques, but is only available on a research basis so far.
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