Technique of sonographic assessment of lower uterine segment in women with previous cesarean delivery: a prospective, pre/intraoperative comparative ultrasound study

Intraoperative ultrasound during repeat cesarean delivery facilitates sampling of uterine scar tissue

OBJECTIVES

Histological examination of uterine scars provides insight into uterine wound healing and helps to develop prevention methods of uterine wall rupture after previous uterine surgery. Therefore, exact intraoperative scar identification is needed for specimen collection from the actual scar tissue. The aim of this study was to correlate pre- and intraoperative ultrasound measurements of the lower uterine segment (LUS) with histological findings of scar tissue and to evaluate the relevance of intraoperative ultrasound.

METHODS

In a prospective observational study, preoperative and intraoperative sonographic measurements of the LUS thickness were performed in 33 women with a history of at least one cesarean delivery. Intraoperative ultrasound with a linear transducer placed directly on the uterus identified the scar area and uterotomy was performed 2 cm cranially. Tissue samples were taken after extraction of the fetus, embedded in paraffin wax, and stained according to Gomori Trichrome to identify scar tissue. Collagen content was evaluated with imaging software Fiji (NIH, Bethesda, USA). Preoperative and intraoperative sonographic measurements were correlated with histologic evidence of scar tissue.

RESULTS

Histological evidence of scar tissue was found in 11 out of 33 samples with significantly lower ultrasonographic thickness of the lower uterine segment compared to the other 22 samples, both antepartum (1.4 mm [1.3-1.9] vs. 2.0 mm [1.6-2.6], p=0.03) and intrapartum (1.6 mm [1.3-1.9] vs. 3.7 mm [2.0-4.7], p<0.01). Intraoperative ultrasound had a significantly higher predictive power (AUC difference 0.18 [0.03-0.33], p=0.01).

CONCLUSIONS

Intraoperative sonography identifies the uterine wall area with histologically confirmable scar tissue far better than preoperative sonography.

Applicability of ultrasonography for detection of marginal sinus placenta previa

This study aimed to examine whether marginal sinus placenta previa, defined as when the marginal sinus just reaches the internal cervical os and placental parenchyma might be >2 cm from the internal cervical os, can be diagnosed using ultrasonography (US). We identified the placenta previa cases that underwent both US and magnetic resonance imaging (MRI) between April 2010 and December 2018 at our institution. The diagnostic discrepancies for marginal sinus placenta previa between US and MRI were examined retrospectively. Of the 183 cases of placenta previa, 28 (15.3%) cases were diagnosed as marginal sinus placenta previa using MRI. Among them, 18 cases (64.3%) could also be diagnosed using US. The sensitivity and specificity of the diagnosis of marginal sinus placenta previa using US were 64.3% and 92.9%, respectively. A change in US diagnosis occurred in 10 (35.7%) cases, all of which were diagnosed with low-lying placenta previa or marginal placenta previa and did not develop any serious miserable obstetrical outcomes. In conclusion, the diagnostic accuracy of US for detecting marginal sinus placenta previa was not significant. MRI examination may be required to accurately categorize the types of placenta previa.

The B-mode sonographic evaluation of the post-caesarean uterine wall and its methodology: A study protocol

AIM

The aim of this study is to utilize the niche measurement guidelines outlined by Jordans et al. in order to establish normal values and accurate description of caesarean section scars in a normal population. After defining the normal distribution, abnormal pregestational scar characteristics will be identified for predicting adverse pregnancy outcomes.

METHODS

This is a prospective observational multicenter clinical study where women with a history of only one caesarean section and yet open family planning are enrolled. The uterine length, cervical length, niche length, niche depth, niche width, residual myometrial thickness, endometrial thickness, scar to internal os distance, anterior myometrial thickness superior and inferior to the scar and the posterior myometrial thickness opposite the scar, superior and inferior to it are measured in a pregestational uterus. The lower uterine segment is measured over a length of 3 cm during subsequent pregnancy and followed up until delivery.

RESULTS

Data from 500 patients will yield normal distribution curves for all predefined measurements. Establishing a correlation between deviations from the normal measures and adverse events would be instrumental for counseling women regarding subsequent pregnancy and mode of delivery.

CONCLUSION

This study will demonstrate the changes of the post-caesarean scar from a non-pregnant uterus until delivery and can confirm the importance of the scar characteristics in predicting pregnancy outcome.