Structural changes in puborectalis muscle after vaginal delivery

Tissue Characterization of Puborectalis Muscle From 3-D Ultrasound

Pelvic floor (PF) muscles have the role of preventing pelvic organ descent. The puborectalis muscle (PRM), which is one of the female PF muscles, can be damaged during child delivery. This damage can potentially cause irreversible muscle trauma and even lead to an avulsion, which is disconnection of the muscle from its insertion point, the pubic bone. Ultrasound imaging allows diagnosis of such trauma based on comparison of geometric features of a damaged muscle with the geometric features of a healthy muscle. Although avulsion, which is considered severe damage, can be diagnosed, microdamage within the muscle itself leading to structural changes cannot be diagnosed by visual inspection through imaging only. Therefore, we developed a quantitative ultrasound tissue characterization method to obtain information on the state of the tissue of the PRM and the presence of microdamage in avulsed PRMs. The muscle was segmented as the region of interest (ROI) and further subdivided into six regions of interest (sub-ROIs). Mean echogenicity, entropy and shape parameter of the statistical distribution of gray values were analyzed on two of these sub-ROIs nearest to the bone. The regions nearest to the bones are also the most likely regions to exhibit damage in case of disconnection or avulsion. This analysis was performed for both the muscle at rest and the muscle in contraction. We found that, for PRMs with unilateral avulsion compared with undamaged PRMs, the mean echogenicity (p = 0.02) and shape parameter (p < 0.01) were higher, whereas the entropy was lower (p < 0.01). This method might be applicable to quantification of PRM damage within the muscle.

Appearance of the levator ani muscle subdivisions on 3D transperineal ultrasound

BACKGROUND

The levator ani muscle (LAM) consists of different subdivisions, which play a specific role in the pelvic floor mechanics. The aim of this study is to identify and describe the appearance of these subdivisions on 3-Dimensional (3D) transperineal ultrasound (TPUS). To do so, a study designed in three phases was performed in which twenty 3D TPUS scans of vaginally nulliparous women were assessed. The first phase was aimed at getting acquainted with the anatomy of the LAM subdivisions and its appearance on TPUS: relevant literature was consulted, and the TPUS scan of one patient was analyzed to identify the puborectal, iliococcygeal, puboperineal, pubovaginal, and puboanal muscle. In the second phase, the five LAM subdivisions and the pubic bone and external sphincter, used as reference structures, were manually segmented in volume data obtained from five nulliparous women at rest. In the third phase, intra- and inter-observer reproducibility were assessed on twenty TPUS scans by measuring the Dice Similarity Index (DSI).

RESULTS

The mean inter-observer and median intra-observer DSI values (with interquartile range) were: puborectal 0.83 (0.13)/0.83 (0.10), puboanal 0.70 (0.16)/0.79 (0.09), iliococcygeal 0.73 (0.14)/0.79 (0.10), puboperineal 0.63 (0.25)/0.75 (0.22), pubovaginal muscle 0.62 (0.22)/0.71 (0.16), and the external sphincter 0.81 (0.12)/0.89 (0.03).

CONCLUSION

Our results show that the LAM subdivisions of nulliparous women can be reproducibly identified on 3D TPUS data.

Pelvic floor assessment using magnetic resonance imaging after vaginal delivery and elective caesarean delivery

INTRODUCTION AND HYPOTHESIS

We aimed to compare quantitative static and dynamic magnetic resonance imaging (MRI) measurements of pelvic floor changes during postpartum recovery from 1 week to 6 months after different modes of delivery.

METHODS

In this prospective study, 51 primiparous women (vaginal delivery group: 30 women; elective caesarean delivery group: 21 women) underwent static and dynamic MRI at 1 week, 6 weeks, 3 months, and 6 months postpartum to measure pelvic floor MRI values. Between-group differences in pelvic floor values at these time points were determined; subsequently, within-group comparisons according to time were performed. Analysis included independent samples t-tests and paired t-tests.

RESULTS

The puborectal hiatus line (H line), muscular pelvic floor relaxation line (M line), bladder-pubococcygeal line (B-PCL), and uterus-pubococcygeal line (U-PCL) differed significantly between groups during the Valsalva manoeuvre at 1 week postpartum (p < 0.05). The H line, M line, and B-PCL values differed significantly between groups during the Valsalva manoeuvre at 6 weeks postpartum (p < 0.05). There were few significant between-group differences in pelvic floor values at 3 months and 6 months postpartum. In the vaginal delivery group, the differences in the H line and M line at 1 week, 6 weeks, and 3 months postpartum were significant (p < 0.001). In the elective caesarean delivery group, U-PCL differed significantly at 6 weeks compared to 1 week postpartum during the Valsalva manoeuvre (p < 0.05).

CONCLUSIONS

Pelvic floor recovery primarily occurred during the early phase after delivery in both groups. Elective caesarean delivery had a non-significant protective effect on postpartum pelvic floor structure and function compared to vaginal delivery.

Deep learning enables automatic quantitative assessment of puborectalis muscle and urogenital hiatus in plane of minimal hiatal dimensions

OBJECTIVES

To measure the length, width and area of the urogenital hiatus (UH), and the length and mean echogenicity (MEP) of the puborectalis muscle (PRM), automatically and observer-independently, in the plane of minimal hiatal dimensions on transperineal ultrasound (TPUS) images, by automatic segmentation of the UH and the PRM using deep learning.

METHODS

In 1318 three- and four-dimensional (3D/4D) TPUS volume datasets from 253 nulliparae at 12 and 36 weeks' gestation, two-dimensional (2D) images in the plane of minimal hiatal dimensions with the PRM at rest, on maximum contraction and on maximum Valsalva maneuver, were obtained manually and the UH and PRM were segmented manually. In total, 713 of the images were used to train a convolutional neural network (CNN) to segment automatically the UH and PRM in the plane of minimal hiatal dimensions. In the remainder of the dataset (test set 1 (TS1); 601 images, four having been excluded), the performance of the CNN was evaluated by comparing automatic and manual segmentations. The performance of the CNN was also tested on 117 images from an independent dataset (test set 2 (TS2); two images having been excluded) from 40 nulliparae at 12 weeks' gestation, which were acquired and segmented manually by a different observer. The success of automatic segmentation was assessed visually. Based on the CNN segmentations, the following clinically relevant parameters were measured: the length, width and area of the UH, the length of the PRM and MEP. The overlap (Dice similarity index (DSI)) and surface distance (mean absolute distance (MAD) and Hausdorff distance (HDD)) between manual and CNN segmentations were measured to investigate their similarity. For the measured clinically relevant parameters, the intraclass correlation coefficients (ICCs) between manual and CNN results were determined.

RESULTS

Fully automatic CNN segmentation was successful in 99.0% and 93.2% of images in TS1 and TS2, respectively. DSI, MAD and HDD showed good overlap and distance between manual and CNN segmentations in both test sets. This was reflected in the respective ICC values in TS1 and TS2 for the length (0.96 and 0.95), width (0.77 and 0.87) and area (0.96 and 0.91) of the UH, the length of the PRM (0.87 and 0.73) and MEP (0.95 and 0.97), which showed good to very good agreement.

CONCLUSION

Deep learning can be used to segment automatically and reliably the PRM and UH on 2D ultrasound images of the nulliparous pelvic floor in the plane of minimal hiatal dimensions. These segmentations can be used to measure reliably UH dimensions as well as PRM length and MEP. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Echogenicity of puborectalis muscle, cervix and vastus lateralis muscle in pregnancy in relation to mode of delivery

OBJECTIVES

To confirm our previous observation that levator hiatal dimensions and mean echogenicity of the puborectalis muscle (MEP) are significantly different at 12 weeks' gestation in women who delivered by Cesarean section due to failure to progress compared with those who delivered vaginally. The secondary objective was to assess the association between the echogenicity of the cervix and vastus lateralis muscle and mode of delivery.

METHODS

In this prospective multicenter study, 306 nulliparous women with a singleton pregnancy underwent ultrasound assessments of the pelvic floor at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva maneuver, of the cervix and of the vastus lateralis muscle at 12 weeks' gestation. Dimensions of the levator hiatus, MEP and mean echogenicity of the cervix and vastus lateralis muscle were measured and compared according to mode of delivery.

RESULTS

Two hundred and forty-nine women were included in the analyses. We were unable to confirm our previous finding that MEP and levator hiatal transverse diameter and area at 12 weeks' gestation are associated significantly with mode of delivery. In addition, we could not demonstrate a significant association between echogenicity of the cervix or vastus lateralis muscle and mode of delivery. Overall, MEP was a mean of 20 points lower in women in the new database as compared with the previous study, despite the use of the same ultrasound equipment.

CONCLUSION

In a second, independent multicenter dataset, we were unable to confirm our previous finding that levator hiatal dimensions and MEP on pelvic floor muscle contraction are associated significantly with mode of delivery. We also found no association between echogenicity of the cervix or vastus lateralis and mode of delivery. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.