Gynaecological ultrasonography has become an integral part of the clinical examination. It is best done by the attending trained Gynaecologist to extend his or her clinical judgement. This is especially so in acute situations and in the areas of pelvic pain, abnormal uterine bleeding, early pregnancy monitoring and fertility investigations. Currently transvaginal scanning has taken over as the standard technique for pelvic examination. Both mechanical and electronic probes with offset or non-offset sound emission patterns could be used for transvaginal gynaecological scanning. For beginners the main difficulty is to convert from abdominal to transvaginal scan orientation. During transabdominal scanning both the monitor and the scanning plane are along the vertical axis. However this relationship is not true during transvaginal scanning as the probe and the monitor are in different planes. To have similar orientation to transabdominal scanning the monitor should be facing the roof during transvaginal scan examinations which is not the case in any of the ultrasound machines so far available.
Pelvic scanning is usually started in the anterior-posterior (AP) plane before rotating the probe into the transverse pelvic plane. In the mid AP position, the pelvis is examined in the sagittal view. Moving the probe to the right or left in the same plane would give right and left AP pelvic views respectively. On the other hand scanning in the transverse pelvic plane is done when the probe is rotated 90o to the right or left to give the right or left transverse pelvic views respectively. The uterus could be examined in AP (including sagittal) or apical (transverse pelvic) views but never in a transverse uterine view during transvaginal scanning. It is only possible to have a transverse view of the uterus during transabdominal scan examinations when the scanning plane is perpendicular to the long axis of the body. This orientation is not possible vaginally.
During transvers pelvic scanning, the right side of the monitor always corresponds to the right side of the patient. However there is no standardisation for AP scanning. This is left for the operators' choice and could be selected by setting the monitor.
The urinary bladder should be empty during transvaginal scanning. However when partly filled it shows a triangular shape in the sagittal view but its outline could be dented by any uterine or ovarian mass pushing on its wall. The course of the urethra and the presence of bladder wall pathology, pararuretheral or vaginal cysts could be easily ascertained with the probe inserted just into the lower vagina. This could be useful when investigating patients with urinary symptoms.
The 3 pictures shown above depict:
Transverse pelvic view of bladder, urethra and 3 pararurethral cysts
Oblique view showing a suspected bladder wall endometriotic nodule
AP and transverse views of the cervix showing multiple nabothian cysts .
The cervix is 4 cm in average length and is more echogenic than the rest of the uterus. Measurements less than 2.5 cm could have clinical significance during investigations of recurrent miscarriages. However, gradual shortening and funnelling during pregnancy might be more important than a single measurement. Nabothian follicles are frequently seen and could give a honeycomb appearance. During the reproductive years the cervix is normally shorter than the long axis of the body of the uterus and more echogenic. With the continuous decline in the uterine size during the postmenpausal years the cervix and the body of the uterus might have the same length or the cervix might even be longer. It is best to examine the cervix in the AP or longitudinal view during the periovulatory period. This could allow diagnosis of such conditions as intracervical polyps which is facilitated by the presence of mucous within the cervical canal. Such polyps could present with intermenstrual or postcoital bleeding. Other pathologies include:
- Cervical fibroids which could lead to difficulties during childbirth
- Cervical ectopic pregnancies seen as dilated barrel shaped cervix
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Cervical carcinoma seen as a bulky and irregular cervix with undetectable cervical canal. Colour Doppler studies could show bizarre vascular arrangements within the suspected area.
The above three picture show:
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Londitudinal view of a cervix showing an endometrial polyp with surrounding mucous.
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Longitudinal view of the cervix showing anterior and posterior cervical fibroids clamping the cervical canal. This patient was delivered by Caesarean section
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Longitudinal view of the cervix and lower uterus showing increased vascular markings in cervical area as depicted by power Doppler. This area proved to be squamous cell carcinoma.
The uterus takes a central place in pelvic scanning. Its position within the pelvis (flexion and version), size and myometrial morphology should be noted. Unlike transabdominal scanning it is not usual to see the uterus and the cervix in the same plane during transvaginal scan examinations.
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Version indicates the relationship of the long axis of the cervical canal to the long axis of the patient's body. Anteversion and retroversion are diagnosed when the lower cervix points backward toward the rectum or foward toward the bladder respectively. In other words, with anteversion the external os points toward the floor and with retroversion the external os points toward the roof in a woman in the lithotomy position.
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Flexion reflects the relationship between the long axis of the body of the uterus and the long axis of the cervical canal. Anteflexion and retroflexion are terms used to indicate the fundus pointing forward toward the bladder or backward toward the rectum respectively.
The indiscriminate interchangable use of the terms version and flexion should not be allowed. The importance of such misnomenclature is demonstrated by cases of retroverted antelfexed or anteverted retroflexed uteri which are important causes of difficult embryo transfer and office hysteroscopy procedures.
Normally the myometrium has homogeneous medium echogenicity which could be disrupted by such conditions as adenomyosis or fibroids. It is made of 3 layers the middle one being the widest. The outer layer contains the subserosal blood vessesl and the inner hypoechoic layer has a clear interface with the endometrium. Disruption of this interface takes special importance when adenomyosis or malignancy are suspected in patients with relevant symptoms. Vascular markings could be seen toward the periphery especially in parous women and during pregnancy and should not be mixed with other pathologies e.g. adenomyosis. A normal uterus has different dimensions during adult life depending on parity and oestrogen status as shown in the table below. Furthermore uterine size increases by 3.2% and 1.8% every day during the follicular and the luteal phases respectively but regains original size during menstrution.
The 3D pictures shown above depict the following findings respectively.
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An arcuate uterus with minimal dent of the top of the cavity and an intact fundus
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A uterus with complete septum and intact fundus
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A uterus with incomplete septum and intact fundus
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A unicornuate uterus showing a banana cavity after saline infusion sonohysterography
Please see the side menu for the chapters titled Fibroids and adenomyosis to complete the picture for uterine pathology
The endometrium is a dynamic tissue which constantly changes texture during the cycle. Normally a very thin endometrial line would be seen on each side of the cavity by the end of menstruation. A thick endometrial echo at this stage would be suggestive of endometrial pathology, polyps or submucous fibroids. An normal endometrium could measure up to 12 mm during reproductive years. When assessed at midcycle it is hypoechoic and trilaminar in shape which facilitates the diagnosis of polyps splitting the central echo. Submucous fibroids are more hypoechoic and tend be seen better pushing on the echogenic secretory endometrium. On the other hand intrauterine adhesions could be seen as:
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irregular endometrial line
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thin endometrium despite good ovulation
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bright or sonolucnet bridges accross the cavity
In addition to these findings there is usually previous history of uterine surgery or infection following a pregnancy. Saline infusion sonohysterography might be the best method for confirming the diagnosis. More information could be found in the chapter titled hypomenorrhoea on the side menu.
The first picture above shows a thin postmenstrual endometrium marked with arrows. The second picture shows a midcycle trilaminar endometrium with 2 hypoechoic areas between the 3 sharp lines. The central echo denotes the cavity and the line of contact between the two endometrial surfaces. Such a straight unbroken line excludes the presence of polyps.
It remains to be said that in some cases of endometritis the endometrium could be thick, heterogeneous with irregular outline and some fluid or debris in the cavity. This picture should be correlated to the clinical presentation as similar findings could be seen in other conditions including endometrial malignancy in postmenopausal women with abnormal uterine bleeding. Obesity, nulliparity, late menopause and use of unopposed oestrogens increases the risk of such a malignancy. On the other hand the endometrium could be diffuse and thick with intact interface with the myometrium in cases of hyperplasia which could also be focal and at the base of broad based polyps. An irregular endometrial / myometerial interface could also be due to focal adenomyosis with the ectopic endometrium pushing through the junctional zone. Endometral thickness should be assessed in the longitudinal [sagittal] uterine plane and the thickest area of the endometrium should be measured. It is important not to include the hypoechoic junctional zone of the myometrium into the measurement.
An endometrial thickness < 5 mm almost excludes the risk of malignancy in cases of postmenopausal bleeding. However a figure up to 8 mm could be normal in obese women, patients on HRT and hypertensive women taking calcium channel blockers. A thick endometrium in non-symptomatic postmenopausal women should not indicate invasive treatment as bleeding is usually the first symptom of malignancy. Such thick endometrium could be due to an endometrial polyp as an example. At the same time endometrial thickness does not carry the same diagnostic weight of sinister pathology in younger symptomatic women within their reproductive age as for postmenopausal ones.
In summary endometrial pathology could be reflected by one of the following findings:
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> 5 mm thick endometrium at the end of menstruation
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abnormaly thick endometrium > 13 mm at other times of the cycle
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abnormally thin endometrium at midcycle
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irregular endometrial / myometrial interface
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indiscriminate endometrial outline
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heterogenous endometrial texure
The presence of fluid in the uterine cavity could be seen in the following conditions:
The ovaries could be seen between the uterus medially and the internal iliac vessels laterally which are good landmarks posterior and lateral to the normally sited ovaries. Transvaginal scanning allows more accurate ovarian measurement and detailed texture assessment. As for the uterus, ovarian size depends on age and endocrine status. The expected average ovarian volume during the reproductive years would be 5.0 - 9.0 ml and they have symmetrical size and characteristic appearance depicted by the presence of few antral follicles within an ovoid structure. Ovarian size before menarche and after the menopause would be around 3 ml. Calculation of ovarian volume is mostly given directly by modern ultrasound machines after recording length, breadth and depth. However, multiplying the 3 measurement by a factor of 0.523 could also be used to calculate ovarian volume. A small ovary < 2 ml with no follicular activity wihin the reproductive years is usually diagnostic of premature ovarian failure. On the other hand a polycystic ovary might be >10 ml in volume. In such cases > 12 small cysts < 9 mm in diameter would be seen either subcapsularly or dispersed over the stroma. Such pattern is seen in women with polycystic ovarian syndrome but is not diagnostic of the condition in isolation. Polycystic ovaries could be seen in women with thyroid problems, hyperprolactinaemia, 21 hydroxylase deficiency as well as in 20% of normal women with no endocrine, menstrual or fertility problems.
After the menopause there is a gradual decline in ovarian size and follicular activity with time. It is important to remember that up to 25% of women within the early postmenopausal year might show simple follicular cysts < 5 cm in diameter. These patients should be followed with repeated ultrasound scan examinations so long as there is no indication for immediate or subsequent surgical intevrention [see ovarian cyst on the side menu]
Displacement of one or both ovaries and significant discrepancy in their size could indicate a pathological condition worth of further investigations. One or both ovaries could be displaced due to uterine retroversion or by pelvic adhesions. Transvaginal ultrasound scanning might fail in revealing these ovaries if they were displaced high behind the fundus of the uterus. In such cases abdominal pressure with the free hand could bring the ovary within reach or transabdominal scanning might be needed to examine that displaced ovary. Other signs of adhesions include encysted fluid in the pelvis, dilated fallopian tubes and failure of the ovaries and uterus to move in different directions during pressure with the probe [negative organs sliding test]
Different types of cysts could change the overall size and texture of the ovaries. Ovarian pathology is best seen during the early follicular phase. After the menopause the ovaries tend to get smaller, hypoechoic and difficult to locate. Occasionally only the right ovary is accessible as the left one might be masked by bowel shadows on the left side. They could also show bright echogenic shadows which are mostly haemosidrin deposits and calcifications. More information would be found in the 'Ovarian Cysts chapter in this website.
Further assessment of the pelvis should include the fallopian tubes which are not usually visible in normal circumstances. However, the fimbrial end could be seen when there is some fluid in the pelvis especially if the patient is put on a semi-sitting position. Furthermore, normal tubes could be seen if an echogenic fluid is instilled into the uterus [see HyCoSy on the side menu]. Nevertheless it is not usually possible to see the whole length of the tube in one plane. A normal tube is 8-12 cm long and has 0.5 mm internal diameter at the interstitial part but up to 1.5 mm in the fimbrial part. Thickening of the wall or dilatation of the lumen with fluid, ectopic pregnancy or a mass would make them more readily visible. A dilated tube is usually retort shape structure beside the uterus with one or more incomplete septae [pseudo septae]. Such hydrosalpinges are best seen during the mid cycel before they drain back after ovulation becuase of the progesterone induced relaxation of the tubo uterine junction [communicating hydrosalpinges]. On the othe hand tubal ectopic pregnancies are best seen in the 'ectopic angle' between the uterus and the epsilateral ovary harbouring the corpus luteum [see ectoptic pregnancy on the side menu]
Examination of the pouch of Douglas could show free or encysted fluid during reproductive years. Such fluid is normally clear but could be turbid if it contained blood or pus cells. Moderate or excessive amount of fluid in the pelvis after the menopuse is abnormal and should raise the supicision of pathology mainly ovarian cancer and hepatic disiease. Rectovaginal endometriosis and pelvic abscesses could as well be seen as heterogeneous masses in the POD. Clinical presentation would help in making the diagnosis.
For further information regarding the use of ultrasound in diagnosing gynaecological pathology please refer to the chapters entitled fibroids, Ovarian cysts, adenomyosis, endometrial polyps, ectopic pregnancy, pelvic congestion syndrome, saline infusion sonohysterography, and HyCoSy.
