SONOELASTOGRAPHY OF THE UTERINE CERVIX AS A NEW DIAGNOSTIC TOOL OF CERVICAL ASSESSMENT IN PREGNANT WOMEN.

SONOELASTOGRAPHY IN PREDICTING PRETERM DELIVERY IN ASYMPTOMATIC, LOW-RISK WOMEN

Despite the efforts to decrease the rate of preterm birth, preterm delivery is still the main cause of neonatal morbidity and mortality responsible for 75% of all neonatal deaths (Goldenberg RL et al, 2008) .

Identifying patients threatened with preterm delivery remains one of the main obstetric challenges , the WHO estimated that 11.1% of all births were preterm (Blencowe H et al, 2012).

Elastography is an ultrasound-based imaging technique visualizing the stiffness of examined region. The technique is based on the phenomenon, that after applying pressure with the probe, soft tissues are compressed in a greater extent than hard tissues and the gradient values of strain are visualized on a color map.

An increasing number of reports shows the possible applications of elastography in obstetrics and gynecology, for instance in predicting the success of induction of labour and differential diagnosis of endometrial pathologies (Preis K et al. 2010), (Swiatkowska-Freund M et al. 2011), (Preis K et al. 2011).

Hernandez-Andrade et al.(2013) reported a continuous reduction in cervical stiffness with decreasing cervical length and increasing gestational age, which manifested mainly in the internal cervical os. It has also been suggested, that elastography may hold potential to predict risk of preterm birth (Khalil MR et al.,2013)

In a study conducted by Slawomir Wozniak. Et al published in July 2014, 333 low-risk, asymptomatic women presenting for the routine second trimester ultrasound scan according to the Polish Gynecological Society recommendation between 18-22 weeks of pregnancy.

Elastographic assessment of the internal os was performed using a color map: red (soft), yellow (medium soft), blue (medium hard) and purple (hard)

Elastographic (left) and ultrasound (right) images of the internal cervical os (circles) at 18-22 weeks of pregnancy. Internal cervical os stiffness was assessed as: A) soft (red); B) medium soft (yellow); C) medium hard (blue); D) hard (purple).

BMC Pregnancy Childbirth. 2014; 14: 238

The number of preterm deliveries (<37 weeks of pregnancy) was significantly higher in the red and yellow groups, than in the blue and purple groups. The sensivity, specifity, NPV and PPV for both red and yellow internal os assessment in predicting preterm delivery were 85.7%, 97.6%, 98.3% and 81.1% respectively.

Accordingly the study concluded the following: 1. Elastographic assessment of the internal cervical

os at 18-22 weeks of pregnancy may identify patients with high risk of preterm delivery in the low-risk, asymptomatic population.

2. Elastographic abnormalities may precede ultrasound and clinical findings, such as cervical shortening and funneling.

QUANTITATIVE SONOELASTOGRAPHY OF THE UTERINE CERVIX PRIOR TO INDUCTION OF LABOR AS A PREDICTOR OF CERVICAL DILATION TIME.

In another study performed by Hee L et al.(2014) A total of 49 term-pregnant women were included before induction of labor. The approximate Young's modulus of the anterior cervical lip was determined by the use of a reference cap applied on the end of the transvaginal transducer during sonoelastography, compared to Bishop scoring and cervical length measurements to predict prolonged duration of cervical dilation time (>330 min)

The following results were shown

Accordingly the study concluded that The approximate Young's modulus is superior to the Bishop score and the cervical length measurements concerning the prediction of cervical dilation time and the risk of prolonged dilation time after induction of labor

Sensitivity Specificty

Approximate Young’s Modulus of Semi quantitative Sonoelastograpgy

74% 69%

Bishop Scoring 53% 46%

Cervical length measurments

66% 54%

Cervical strain calculation performed in: a) endocervical canal in a sagittal plane, b) endocervical canal in a cross sectional plane at the level of the internal os, c) endocervical canal in a cross sectional plane at the level of the external cervical os, and d) complete cervix in a cross sectional plane at the level of the external cervical os.

NIHPA , Ultrasound Obstet Gynecol, Sep 11, 2014

OTHER CLINICAL APPLICATIONS OF SONOELASTOGRAPHY IN OBSTETRICS AND GYNECOLOGY

To characterize malignant cervical lesions in postmenopausal women (Thomas A. et al. 2007)

To assess stiffness in uterine fibroids compared with the surrounding myometrium in non-pregnant women (Ami O. et al . 2009)

To evaluate tissue differences in the presence of subchorionic hematomas (Ogawa M. et al. 2012)

Differentiation between polyps and leiomyomas (Hobson MA. et al. 2007)

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