Ultrasound signs of uterine abnormalities

Myometrial pathology

Currently, given the widespread introduction of transvaginal ultrasound into clinical practice, diagnostics of pathological changes in the myometrium does not present significant difficulties. However, the information content of ultrasound diagnostics for various myometrial pathologies is not the same.

Ultrasound scanning is the most informative method for diagnosing uterine fibroids. Transabdominal ultrasound before hysteroscopy is used to determine the location and size of fibroid nodes. However, only the high resolution of transvaginal sensors allows for a more detailed study of the size, location and structure of fibroid nodes, and to identify very small nodes, especially in obese patients. Second only to laparoscopy and hysteroscopy for subserous and submucous localization of fibroid nodes, respectively, transvaginal scanning is the leading method for diagnosing intermuscular nodes. The accuracy of determining submucous and interstitial nodes with centripetal (towards the uterine cavity) growth is 95.7%.

Ultrasound criteria for uterine fibroids: increase in the size and contours of the uterus, the appearance of round structures with increased sound conductivity in the myometrium or uterine cavity.

There are acoustic criteria for dystrophic transformation of uterine myomatous nodes detected by transabdominal ultrasound:

1. Areas of increased echogenicity without clear boundaries.
2. Anechoic cystic inclusions.
3. Phenomenon of acoustic amplification along the periphery of a node.

A.N. Strizhakov and A.I. Davydov (1997) during transvaginal ultrasound examination identified histologically verified ultrasound signs of proliferating uterine myoma: the presence of echo-negative areas in combination with tumor fragments of medium echogenicity. According to the authors, the ratio of cystic and dense components of the myoma varies depending on the degree of expression of proliferative processes.

In ultrasound diagnostics of submucous or intermuscular uterine myoma with centripetal growth, special attention should be paid to the condition of the midline uterine structure (degree of M-echo deformation). In ultrasound, submucous myoma nodes are visualized as round or ovoid formations with smooth contours and medium echogenicity, located in the expanded uterine cavity. As a rule, only large submucous nodes change the shape of the uterine cavity. With small tumor sizes, only an increase in the anteroposterior size of the M-echo is noted.

With centripetal growth of the interstitial node, a deformed uterine cavity with smooth contours is always determined (regardless of the size of the node). In this case, acoustic signs of myoma are visualized both near the concave surface of the uterine cavity and M-echo, and in the adjacent myometrium.

Considering that the accuracy of diagnostics of submucosal and intermuscular uterine myomas with centripetal growth increases against the background of uterine bleeding (the blood accumulated in the uterine cavity acts as a kind of natural contrast), in recent years hydrosonography has been widely used for this pathology. The introduction of a contrast agent into the uterine cavity allows for a more accurate determination of the size of the formation, the spatial relationship of the tumor to the walls of the uterine cavity and the severity of the intermuscular component of the myomatous node.

Intrauterine ultrasound

The accuracy of ultrasound diagnostics of submucous uterine myoma will increase significantly in the future with the introduction of intrauterine ultrasound into practice. It is performed using special sensors with an expanded uterine cavity, which is especially important, since the conditions of the method are as close as possible to those during transcervical resection of myomatous nodes. This method can provide the most valuable information about the size of the intramural component of the submucous node even before the operation.

More objective information about uterine fibroids can be obtained using three-dimensional ultrasound, which is increasingly used in gynecology.

To assess peripheral hemodynamics in patients with uterine myoma and the degree of vascularization of myomatous nodes, Doppler studies and color Doppler mapping are used. In uterine myoma, a reliable decrease in vascular resistance in the uterine arteries has been proven, which indicates an increase in arterial blood flow. A decrease in the resistance index in the vessels of a myomatous node is characteristic of its necrosis, secondary degeneration, and inflammatory processes. Color Doppler mapping allows detecting myomatous nodes with pronounced vascularization, which, according to Friedman et al. (1987), correlates with the effectiveness of therapy with gonadotropin-releasing hormone (GnRH) analogues.

In recent years, great importance has been attached to highly informative instrumental methods of examination in the diagnosis of adenomyosis, including ultrasound scanning. At the same time, only transvaginal ultrasound allows for a high degree of accuracy in diagnosing endometriosis damage to the muscular layer of the uterus.

Pathognomonic acoustic criteria of internal endometriosis have been developed: enlargement of the uterus (mainly due to the anteroposterior size) with asymmetric thickening of the anterior and posterior walls, rounded shape of the uterus, appearance of abnormal cystic cavities in the myometrium, heterogeneity of the echogenic structure of the myometrium, unclear border between the endometrium and the myometrium, etc. However, according to various authors, the accuracy of diagnosing adenomyosis using transvaginal ultrasound does not exceed 62-86%. This is explained by the fact that even with transvaginal adenomyosis it is not always possible to distinguish endometrioid cavities in the myometrium from false echo signals (for example, dilated vessels in chronic endometritis), an increase in the anteroposterior size of the uterus in adenomyosis from that in other pathological conditions of the uterus (for example, uterine fibroids), etc. It should be emphasized that the detection of true endometrioid cavities (cystic cavities of irregular shape, surrounded by a thin echo-positive line) becomes possible, as a rule, only at II-III degrees of prevalence of the pathological process according to the classification of B.I. Zheleznov and A.N. Strizhakov (1985).

The diagnosis of the nodular form of the disease is less complicated. The use of high-frequency transvaginal sensors allows for clear differentiation of adenomyosis nodes and uterine myoma. The main acoustic criterion for adenomyosis nodes is the absence of a surrounding connective tissue capsule, which is characteristic of interstitial uterine myoma.

Color Doppler mapping helps in the differential diagnosis of the nodular form of adenomyosis and small uterine fibroids: adenomyosis nodes are visualized more clearly and brightly than fibroids, which, unlike adenomyosis, are characterized by a surrounding bright color rim, representing the reflection of an ultrasound wave from the connective tissue capsule.

Pathology of the endometrium

The ultrasound image of endometrial polyps depends on their number, size, location and shape. Polyps are visualized inside the expanded uterine cavity as round or ovoid formations, usually with smooth contours. Unlike submucous myomatous nodes, endometrial polyps are characterized by lower echogenicity. As a rule, they do not change the shape of the uterus (with the exception of large polyps).

Endometrial polyps are easier to diagnose with uterine bleeding, in which case the polyp is well contrasted and clearly visible, since it does not merge with the walls of the uterus and the endometrium.

The use of a contrast agent during transvaginal ultrasound significantly facilitates the diagnosis of endometrial polyps. Our accumulated experience in hydrosonography shows the high information content of this method in the differential diagnosis of various types of intrauterine pathology. Endometrial polyps clearly stand out against the background of the contrast fluid.

The most accurate methods for diagnosing hyperplastic processes and endometrial cancer are hysteroscopy and histological examination of scrapings of the mucous membrane of the uterine cavity. However, given the high information content and minimal invasiveness of transvaginal ultrasound, it is given an important role both in mass examination of women (especially in postmenopause and against the background of hormone replacement therapy) and in the differential diagnosis of various pathological conditions of the mucous membrane of the uterine cavity, accompanied by uterine bleeding.

The diagnosis of endometrial hyperplasia by ultrasound is based on the detection of an enlarged median M-echo with increased acoustic density in the anteroposterior size. The structure of the hyperplastic endometrium can be either homogeneous or with echo-negative inclusions (difficult to distinguish from endometrial polyps). A second type of endometrial hyperplasia has also been described, in which the hyperechoic smooth thickened contours of the endometrium on the echogram limit the hypoechoic homogeneous zone.

Transvaginal ultrasound is of great importance in examining postmenopausal patients to prevent malignant transformation of the endometrium. According to numerous studies, the risk group among postmenopausal patients includes women who show an increase in the anteroposterior size of the midline structure of the uterus with increased echogenicity during ultrasound.

To date, there are no clear criteria for endometrial pathology in asymptomatic postmenopausal patients; according to various authors, the upper limit of endometrial thickness varies from 5 to 10 mm. At the same time, in the presence of any symptoms in postmenopausal women, the criterion for pathological changes in the endometrium is considered to be an endometrial thickness of 4 mm or more. On the other hand, the authors believe that a very thin endometrium that cannot be measured by ultrasound, which is also typical for postmenopausal patients, does not exclude endometrial pathology. Fluid accumulation in the uterine cavity detected by repeated ultrasound should be alarming; in this case, additional invasive diagnostics are necessary. According to Timmerman and Vergote (1997), if all patients with such a borderline endometrial thickness undergo additional invasive diagnostics (hysteroscopy, separate diagnostic curettage), the number of surgical interventions can be reduced by 50%.

Endometrial cancer

The possibilities of ultrasound diagnostics of endometrial cancer are limited, since, according to most researchers, malignant transformation of the endometrium has no specific echographic signs. Promising studies on the use of color Doppler mapping in the diagnosis of endometrial cancer have not found adequate confirmation. To increase the diagnostic capabilities of transvaginal ultrasound for the purpose of differential diagnostics between a polyp, myomatous node and endometrial thickening (hyperplasia or cancer), hydrosonography is recommended.

It is believed that, unlike transabdominal ultrasound, transvaginal examination can be used to determine the stage of the disease based on the depth of myometrial invasion:

• Stage Ia - there are no ultrasound signs of myometrial invasion.
• Stage Ib - myometrial invasion of more than 50%. In this case, the diameter of the endometrial echo is more than 50% of the anteroposterior size of the uterus.
• Stage II - the tumor extends to the cervix. There is no clear demarcation line between the endometrial echo and the cervical canal.

It should be emphasized that the main role assigned to transvaginal ultrasound in detecting endometrial cancer is screening of high-risk patients: postmenopausal women with a history (family history) of breast, ovarian, and uterine cancer. If endometrial thickening or an unclear ultrasound picture is detected, invasive diagnostics are performed. A special high-risk group is postmenopausal women with breast cancer taking tamoxifen. It has been proven that they are more likely to develop endometrial hyperplasia, polyps, and endometrial cancer.

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Pregnancy complications

Ultrasound allows early detection of most complications at their preclinical stage. In the presence of disease symptoms, ultrasound allows timely selection of optimal treatment tactics and determination of indications for hysteroscopy.

One of the most common complications of the first trimester of pregnancy is termination of pregnancy. Various stages of the abortion have a characteristic echographic picture.

The ultrasound image of an incomplete abortion depends on the gestational age and the number of parts of the ovum released from the uterus. The size of the uterus in an incomplete abortion is less than the expected gestational age. The uterine cavity contains many separate, irregularly shaped structures with varying echogenicity, while the ovum has a flattened shape. The echogram often resembles an ultrasound image of a non-developing pregnancy or the initial form of a hydatidiform mole. In a complete abortion, the uterine cavity is usually not expanded, the endometrium is relatively thin and uniform.

The most common ultrasound picture of a non-developing pregnancy is anembryony, or an empty ovum, i.e. the absence of an embryo in the cavity of the ovum, measuring more than 24 mm in transabdominal and more than 16 mm in transvaginal ultrasound. Despite the absence of an embryo, the size of the ovum and uterus can increase until the 10th-12th week of pregnancy, after which their growth usually stops and clinical symptoms of a miscarriage appear. Research by Kurjak et al. (1991) showed that in some cases, color Doppler mapping shows vascularization of empty ovums, the degree of which depends on the activity of the trophoblast. The authors believe that the severity of vascularization can be used to predict in which cases of this pathology there is a risk of a hydatidiform mole.

A diagnosis of non-developing pregnancy is also made by ultrasound in the absence of heartbeats in an embryo whose length exceeds 6 mm. Color Doppler mapping is of great help in this pathology. In the case of recent fetal death, the ovum and embryo have a normal shape and size, and there may be no clinical signs of a threat of termination of pregnancy. If the dead embryo has been in the uterus for a longer period, ultrasound reveals sharp changes in the structure of the ovum, and visualization of the embryo is usually not possible.

Ultrasound is the most accurate method for diagnosing a hydatidiform mole. The diagnosis is based on the detection of multiple echo signals in the uterine cavity, creating a "snow storm" picture. The longer the pregnancy, the more accurate the diagnosis, which is due to the increase in the size of the bubbles (the picture becomes more distinct).

Ultrasound diagnostics of partial hydatidiform mole during pregnancy of more than 12 weeks is also not difficult if the fetus develops normally. With minor changes in the chorion and/or severe degeneration of the fetus, detection of this pathology is often difficult. Differential diagnosis should be carried out with uterine myoma with secondary changes in myomatous nodes (edema, necrosis). Difficulties in differential diagnostics of hydatidiform mole with non-developing pregnancy with significant regressive changes are possible.

The ultrasound criterion for trophoblast invasion during transvaginal ultrasound is the appearance of focal echogenic areas in the myometrium, which may be surrounded by even more echogenic trophoblast tissue.

Transvaginal color Doppler sonography provides valuable information in the diagnosis of trophoblastic disease (invasive hydatidiform mole and choriocarcinoma). Identification of areas of increased vascularization in the myometrium (dilated spiral arteries and newly formed vessels feeding the tumor) using color Doppler sonography allows for the diagnosis of this pathology at an earlier stage. In this case, the uteroplacental vessels reflect ultrasound worse than in a normal pregnancy. Color Doppler sonography also helps in the differential diagnosis of gestational trophoblastic disease with residual ovum after an abortion and endometrial pathology.

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Malformations of the uterus

It is extremely important to identify uterine malformations before performing hysteroscopy. Echographic diagnostics of uterine malformations presents certain difficulties, and the information content of this method in identifying a particular pathology is low.

Diagnosis of a bicornuate uterus and its duplication by ultrasound is not difficult. The transverse size of the uterus prevails over the longitudinal one; echograms show two separate uteruses, connected in the area of the isthmus or slightly higher; sometimes visualization of two M-echo is possible.

The uterine septum is not always visible and is determined on the echogram as a thin-walled structure running in the anteroposterior direction; it creates the impression that the uterus consists of two parts. According to S. Valdes et al. (1984), it is impossible to distinguish a bicornuate uterus from a complete or incomplete septum in the uterine cavity. At the same time, Fedele et al. (1991) describe differential echographic signs of these uterine malformations to determine the tactics of surgical treatment. During ultrasound, 3 points are determined: the orifices of both fallopian tubes and the apex of its fundus protruding into the uterine cavity. The uterus is classified as bicornuate or double if the 3rd point is below the expected line between the orifices of the fallopian tubes or no more than 5 mm above it. In such a situation, hysteroscopic correction of the defect is impossible. In cases where the 3rd point is more than 5 mm above the line connecting the mouths of the fallopian tubes, a diagnosis of partial or complete septum in the uterine cavity is made; elimination of such a developmental defect of the uterus is considered possible with hysteroscopy.

Intrauterine adhesions

The capabilities of ultrasound in diagnosing intrauterine adhesions are limited. In some cases, irregular contours of the endometrium are visualized; in the presence of hematometra, an anechoic formation filling the uterine cavity is determined.

In amenorrhea, transvaginal ultrasound can be used to determine endometrial proliferation against the background of estrogen stimulation. This allows us to determine what part of the uterine cavity is covered by functional endometrium, which facilitates treatment and is very important in determining the prognosis. Hydrosonography allows us to identify single intrauterine adhesions in cases where there is no complete obstruction in the lower part of the uterine cavity.

Complications of intrauterine contraception

When the IUD is removed under hysteroscopy control, a preliminary ultrasound examination is mandatory. The ultrasound image created by the IUD depends on the shape and type of the contraceptive. Each type of IUD has a characteristic clear echogenic image that can change depending on the location of the contraceptive in the uterus. The optimal location of the IUD is when its distal part is localized in the fundus, and the proximal part does not reach the level of the internal os.

In case of pathological displacement of the IUD, its proximal part is visualized in the upper third of the cervical canal. The most serious complication of intrauterine contraception is uterine perforation. It can be incomplete (the IUD penetrates the myometrium) or complete (the IUD partially or completely extends beyond the uterus).

If there is an IUD in the uterine cavity, pregnancy may occur. In the early stages, it is not difficult to detect an IUD: it is located outside the ovum and, as a rule, in the lower part of the uterus.

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Postpartum complications

In diagnostics of postpartum diseases of the uterus before performing hysteroscopy, ultrasound is of primary importance. Ultrasound allows dynamic monitoring of postpartum involution of the uterus, assessment of the condition of the uterine cavity, the suture on the uterus after cesarean section, which is of great importance for choosing adequate treatment tactics.

The accuracy of ultrasound diagnostics of placental tissue retention is almost 100%. The diagnosis in the first days after birth is made based on the detection of an echogenic formation with uneven contours and a spongy structure in the expanded uterine cavity. Subsequently, the echogenicity of the retained placental lobe increases. A placental polyp in transvaginal ultrasound is determined as an oval-shaped formation with a pronounced hyperechoic structure.

The ultrasound picture of endometritis during transvaginal ultrasound is characterized by an increase in the anteroposterior size of the uterine cavity and the accumulation of structures of varying echo density in it. In a number of observations, small hyperechoic inclusions are determined against the background of an unexpanded uterine cavity and, what is especially important, the increased echogenicity of the walls of the uterine cavity, caused by the inflammatory process, attracts attention.

Evaluation of the condition of the uterine suture after cesarean section. It is possible to visualize hematomas under the vesicouterine fold of the peritoneum (they are often not clinically diagnosed) and abscesses in the area of the uterine suture. Such ultrasound indicators of inflammatory changes in the area of the uterine sutures as decreased echogenicity, the appearance of linear structures with pronounced echogenicity, heterogeneity of the myometrium structure, merging of individual reflections from the suture material into solid lines, etc. are distinguished.

Failure of the uterine suture is diagnosed based on the detection of a defect in the form of a deep triangular niche; it is possible to determine the thinning of the myometrium in the suture area.