The evolution of transperineal ultrasound findings of the external anal sphincter during the first years after childbirth

Functional Assessment of Anal Sphincter with Transperineal Ultrasound and Its Relationship to Anal Continence

BACKGROUND/OBJECTIVES

Anal incontinence is linked to pelvic floor dysfunction. Diagnosis involves assessing both the function and structure of the anorectal unit. Although transperineal ultrasound has gained attention as a less invasive option, its effectiveness as a diagnostic tool for evaluating the relationship between structure and function is still debated. This study aimed to explore the relationship between quantitative measurements of anal sphincter and pelvic floor structures as well as the subjective symptoms and objective assessments of sphincter function regarding anal incontinence.

METHODS

50 women with pelvic floor dysfunction were recruited for the study. The severity of anal incontinence was assessed using the CACP score. Ultrasound imaging was employed to measure anal sphincter area, while sphincter pressures were evaluated through manometry. The relationships between variables were analyzed using Pearson's and Spearman's correlation tests.

RESULTS

The mean anal sphincter area was 5.51 cm2 at rest and 4.06 cm2 during maximal contraction. Resting anal sphincter pressure had an average of 46.29 mmHg, and contraction pressure averaged 103.25 mmHg. No significant correlation was found between the anal sphincter area and pressure at rest (r = 0.018) or during contraction (r = -0.210). However, a moderate correlation was observed between the change in sphincter pressure and area during contraction (r = 0.312). The CACP score showed no significant correlation with the sphincter area at rest (r = -0.084) but was weakly correlated during contraction (r = -0.270).

CONCLUSIONS

Conventional diagnostic tools for evaluating anal incontinence can be uncomfortable and are not always readily available. Perineal sonography presents a promising, less invasive alternative for dynamic assessment of the anal sphincter.

Obstetric anal sphincter injury (OASI) in the presence of an intact perineum

Obstetric anal sphincter injury (OASI) in the absence of concurrent injury to the perineal skin is not a common diagnosis. A primiparous woman delivered a healthy male infant by spontaneous vertex delivery. At time of delivery, a compound presentation of the fetal hand with the head was noted. Initial examination revealed a presumed second-degree tear; however, a small laceration above the anal verge was noted, which on exploration revealed a perineal injury through the anal sphincter complex. In the operating theatre, the perineal skin was incised to reveal a 3c OASI, which was repaired appropriately. While atypical OASI has been reported previously, this specific injury has never been described in detail in the literature. Awareness of atypical perineal injuries is needed and while careful perineal examination is required in all cases, this is especially important where the perineal skin appears intact to ensure appropriate diagnosis of any concurrent OASI.

Can transperineal ultrasound improve the diagnosis of obstetric anal sphincter injuries?

INTRODUCTION AND HYPOTHESIS

Women with missed obstetric anal sphincter injuries (OASIs) are at an increased risk of anal incontinence. Our aim was to assess the accuracy of three-dimensional (3D) transperineal ultrasound (TPUS) compared with clinical examination for detecting OASIs.

METHODS

A cross-sectional study of women undergoing their first vaginal delivery. Perineal trauma was initially assessed by the doctor or midwife performing the delivery (accoucheur) and women were then re-examined by the trained research fellow (KW). A 3D TPUS was performed immediately after delivery before suturing to identify OASIs. The research fellow's clinical diagnosis was used as the reference standard. A power calculation determined that 216 women would be required for the study.

RESULTS

Two hundred and sixty-four women participated and 226 (86%) delivered vaginally. Twenty-one (9%) sustained OASIs. Six (29%) of these tears were missed by the accoucheur but were identified by the research fellow. TPUS identified 19 of the 21 (90.5%) OASIs. One percent (n = 2) had sonographic appearances of an anal sphincter defect that was not seen clinically. The positive and negative predictive value of TPUS to detect OASIs was 91% and 99% respectively. TPUS identified 91% of OASIs compared with 71% detected by the accoucheur, which was not statistically significant.

CONCLUSIONS

The detection rate of OASIs with TPUS and with the clinical findings of the accoucheur was similar. Given the training and financial implications needed for TPUS, attention needs to be focused on the training of midwives and doctors to identify anal sphincter injuries by clinical examination.

Is age at menarche a predictor of maternal birth trauma?

OBJECTIVE

Age at menarche and the interval between menarche and age at first vaginal birth have been shown to be associated with reproductive performance; however, their association with maternal birth trauma has not been studied. We aimed to determine whether age at menarche, age at first vaginal birth and their interval are associated independently with levator ani muscle (LAM) avulsion and external anal sphincter (EAS) defect.

METHODS

This was a retrospective analysis of the ultrasound volume datasets of 466 vaginally parous patients attending one of two tertiary urogynecological units in Australia. All patients had undergone a standardized interview and clinical examination using the pelvic organ prolapse quantification staging system, followed by four-dimensional translabial ultrasound. Tomographic ultrasound imaging was used to evaluate the LAM for avulsion and the EAS for significant defect.

RESULTS

Of the 466 women analyzed, LAM avulsion was diagnosed in 121 (26.0%) and significant EAS defect in 55 (11.8%). Logistic regression analysis showed no association between age at menarche and LAM avulsion (P = 0.67). Weak but significant associations were noted between LAM avulsion and age at first vaginal birth (odds ratio (OR), 1.070 (95% CI, 1.03-1.11); P = 0.0007) and between LAM avulsion and menarche-to-first-vaginal-birth interval (OR, 1.064 (95% CI, 1.02-1.11); P = 0.0018). No significant associations were noted between significant EAS defect and any of the evaluated variables (all P ≥ 0.49).

CONCLUSIONS

Age at menarche is not predictive of maternal birth trauma i.e. LAM avulsion and EAS residual defect. There was a statistically significant association between LAM avulsion and menarche-to-first-vaginal-birth interval; however, this was not stronger than the previously established association between LAM avulsion and age at first vaginal birth, arguing against any distinct effect of prolonged prepregnancy hormonal stimulation on the biomechanical properties of the pelvic floor. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Perineal ultrasound in infants with anteriorly displaced anus: A new decision-making tool for the surgeon?

BACKGROUND

Anteriorly displaced anus (ADA) is defined as anterior displacement of the anus toward the perineum. Early radiologic characterization is a crucial step in guiding the first-line management.

OBJECTIVE

The objective of this study was to assess the urethra-to-anus distance (UAD) on perineal ultrasound in female infants under the age of 3 months with anteriorly displaced anus and to retrospectively determine a cut-off to guide the indications for surgery.

MATERIALS AND METHODS

Perineal ultrasound was performed prospectively in female infants under the age of 3 months with determination of the UAD, during screening for congenital hip dislocation. Determinations of the UAD on perineal ultrasound and pelvic MRI were performed for anteriorly displaced anus in girls between 2011 and 2018.

RESULTS

230 patients were included, of whom 173 were in the control group, with 52 examinations performed for anteriorly displaced anus and 5 examinations performed for vestibular anus. The mean UAD for infants under the age of 3 months was: 22.9 mm (±1.7) in healthy infants, 21.4 mm (±2.4) in infants with non-operated ADA, 17.5 mm (±1.8) in infants with operated ADA, and 10.8 mm (±1.3) in infants with anorectal malformation (ARM). A statistically significant difference was observed between the control group and the ARM group (p = 0.0001) and between the control group and the operated ADA group (p = 0.0001). The mean UAD for infants over the age of 3 months was: 25.5 mm (±4.1) in infants with non-operated ADA and 26 mm (±3) in infants with operated ADA.

CONCLUSION

A urethra-to-anus distance of less than 17 mm appears to be a cut-off for anteriorly displaced anus in anorectal malformations.

How comparable is clinical grading of obstetric anal sphincter injury with that determined by four-dimensional translabial ultrasound?

OBJECTIVES

To evaluate the agreement between grading of obstetric anal sphincter injuries (OASI) on translabial ultrasound (TLUS), using a newly developed algorithm, and grading on postpartum examination. A secondary aim was to assess the correlation between tear severity, as defined on ultrasound, and symptoms of anal incontinence and/or fecal urgency.

METHODS

This was a retrospective study of patients seen at a perineal clinic between 2012 and 2018, after recent primary repair of OASI. All patients underwent a standardized interview including the St Mark's anal incontinence test and four-dimensional TLUS. Post-processing of ultrasound volume data was performed blinded to all other data. Using tomographic ultrasound imaging, a set of eight slices was obtained, and the central six slices were evaluated for sphincter abnormalities. Slices with distortion, thinning or defects were rated as abnormal. The following algorithm was used to grade OASI: a Grade-3a tear was diagnosed if the external anal sphincter (EAS) was abnormal in < 4/6 slices; a Grade-3b tear was diagnosed if the EAS was abnormal in ≥ 4/6 slices; and a Grade-3c/4 tear was diagnosed if both the EAS and internal anal sphincter were abnormal in ≥ 4/6 slices. Clinical grading of OASI was determined according to the Royal College of Obstetricians and Gynaecologists guidelines. Agreement between clinical and TLUS diagnosis of OASI was evaluated using weighted κ.

RESULTS

Of the 260 women seen during the study period, 45 (17%) were excluded owing to missing data or a repeat OASI, leaving 215 complete datasets for analysis. The average follow-up interval was 2.4 months (range, 1-11 months) after OASI and the mean age of the women was 29 years (range, 17-42 years). One hundred and seventy-five (81%) women were vaginally primiparous. OASI was graded clinically as Grade 3a in 87 women, Grade 3b in 80, Grade 3c in 29 and Grade 4 in 19. On imaging, full agreement between clinical and TLUS grading was noted in 107 (50%) women, with a weighted κ of 0.398. In 96 (45%) women, there was disagreement by one category, with a weighted κ of 0.74 and in 12 (6%) there was disagreement by two categories. Twenty-four (11%) women were found to have a normal anal sphincter on imaging. Overall, potential clinical over-diagnosis was noted in 72 (33%) women and potential under-diagnosis in 36 (17%). The seniority of the diagnosing obstetrician did not significantly alter agreement between clinical and sonographic OASI grading (κ 0.44, 0.43, and 0.34, for specialists and senior and junior residents, respectively). The association between symptoms of anal incontinence and/or fecal urgency and TLUS grading did not reach significance (P = 0.052).

CONCLUSIONS

Clinical and TLUS-based grading of OASI showed fair agreement. Clinical over-diagnosis may be increasingly common in our population, although under-diagnosis may still occur in a significant minority. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Risk of obstetric anal sphincter injuries (OASIS) and anal incontinence: A meta-analysis

BACKGROUND

Obstetric anal sphincter injuries (OASIS) are the commonest cause of anal incontinence in women of reproductive age. We determined the risk of anal sphincter defects diagnosed by ultrasound, and the risk of anal incontinence in (i) all women who deliver vaginally, (ii) in women without clinical suspicion of OASIS, and (iii) after primary repair of sphincter injury, by systematic review.

METHODS

We searched major databases until June 2018, without language restrictions. Random effects meta-analysis was used to obtain pooled estimates of ultrasound diagnosed OASIS and risk of anal incontinence symptoms at various time points after delivery, and of persistent sphincter defects after primary repair. We reported the association between ultrasound diagnosed OASIS and anal incontinence symptoms using relative risk (RR) with 95 % CI.

RESULTS

We included 103 studies involving 16,110 women. Of all women who delivered vaginally, OASIS were diagnosed on ultrasound in 26 % (95 %CI, 21-30, I² = 91 %), and 19 % experienced anal incontinence (95 %CI, 14-25, I² = 92 %). In women without clinical suspicion of OASIS (n = 3688), sphincter defects were observed in 13 % (10-17, I² = 89 %) and anal incontinence experienced by 14 % (95 % CI: 6-24, I² = 95 %). Following primary repair of OASIS, 55 % (46-63, I² = 98 %) of 7549 women had persistent sphincter defect with 38 % experiencing anal incontinence (33-43, I² = 92 %). There was a significant association between ultrasound diagnosed OASIS and anal incontinence (RR 3.74, 2.17-6.45, I² = 98 %).

INTERPRETATION

Women and clinicians should be aware of the high risk for sphincter defects following vaginal delivery even when clinically unsuspected. This underlines the need of careful and systematic perineal assessment after birth to mitigate the risk of missing OASIS. We also noted a high rate of persistent defects and symptoms following primary repair of OASIS. This dictates the need for provision of robust training for clinicians to achieve proficiency and sustain competency in repairing OASIS.

Exoanal Imaging of the Anal Sphincters

Since its introduction in the early 1990s, endoanal sonography has become the mainstay of morphologic assessment of the anal canal and sphincter, especially for obstetric anal sphincter trauma. Lack of availability of suitable systems and the invasive nature of the method have limited uptake and clinical utility. More recently, exoanal or transperineal/translabial tomographic imaging has been developed as a noninvasive alternative. This pictorial overview aims to introduce the reader to this new diagnostic modality and to demonstrate common findings in asymptomatic and symptomatic women.