Validation of new ultrasound algorithm for estimating prevalence of anal sphincter trauma in a urogynecological population

Predictive factors for obstetric anal sphincter injury in primiparous women: systematic review and meta-analysis

OBJECTIVES

The primary objective was to perform a systematic review of predictive factors for obstetric anal sphincter injury (OASI) occurrence at first vaginal delivery, with the diagnosis made by ultrasound (US-OASI). The secondary objective was to report on incidence rates of sonographic anal sphincter (AS) trauma, including trauma that was not clinically reported at childbirth, among the studies providing data for our primary objective.

METHODS

We conducted a systematic search of MEDLINE, EMBASE, Web of Science, CINAHL, The Cochrane Library and ClinicalTrials.gov databases. Both observational cohort studies and interventional trials were eligible for inclusion. Study eligibility was assessed independently by two authors. Random-effects meta-analyses were performed to pool effect estimates from studies reporting on similar predictive factors. Summary odds ratio (OR) or mean difference (MD) is reported with 95% CI. Heterogeneity was assessed using the I2 statistic. Methodological quality was assessed using the Quality in Prognosis Studies tool.

RESULTS

A total of 2805 records were screened and 21 met the inclusion criteria (16 prospective cohort studies, three retrospective cohort studies and two interventional non-randomized trials). Increasing gestational age at delivery (MD, 0.34 (95% CI, 0.04-0.64) weeks), shorter antepartum perineal body length (MD, -0.60 (95% CI, -1.09 to -0.11) cm), labor augmentation (OR, 1.81 (95% CI, 1.21-2.71)), instrumental delivery (OR, 2.13 (95% CI, 1.13-4.01)), in particular forceps extraction (OR, 3.56 (95% CI, 1.31-9.67)), shoulder dystocia (OR, 12.07 (95% CI, 1.06-137.60)), episiotomy use (OR, 1.85 (95% CI, 1.11-3.06)) and shorter episiotomy length (MD, -0.40 (95% CI, -0.75 to -0.05) cm) were associated with US-OASI. When pooling incidence rates, 26% (95% CI, 20-32%) of women who had a first vaginal delivery had US-OASI (20 studies; I2  = 88%). In studies reporting on both clinical and US-OASI rates, 20% (95% CI, 14-28%) of women had AS trauma on ultrasound that was not reported clinically at childbirth (16 studies; I2  = 90%). No differences were found in maternal age, body mass index, weight, subpubic arch angle, induction of labor, epidural analgesia, episiotomy angle, duration of first/second/active-second stages of labor, vacuum extraction, neonatal birth weight or head circumference between cases with and those without US-OASI. Antenatal perineal massage and use of an intrapartum pelvic floor muscle dilator did not affect the odds of US-OASI. Most (81%) studies were judged to be at high risk of bias in at least one domain and only four (19%) studies had an overall low risk of bias.

CONCLUSION

Given the ultrasound evidence of structural damage to the AS in 26% of women following a first vaginal delivery, clinicians should have a low threshold of suspicion for the condition. This systematic review identified several predictive factors for this. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Is posterior compartment prolapse associated with anal incontinence?

OBJECTIVE

It has been claimed that manifestations of posterior compartment prolapse, such as rectocele, enterocele and intussusception, are associated with anal incontinence (AI), but this has not been studied while controlling for anal sphincter trauma. We aimed to investigate this association in women with intact anal sphincter presenting with pelvic floor dysfunction.

METHODS

This retrospective study analyzed 1133 women with intact anal sphincter presenting to a tertiary urogynecological center for pelvic floor dysfunction between 2014 and 2016. All women underwent a standardized interview, including assessment of symptoms of AI, clinical examination and three-/four-dimensional transperineal ultrasound. Descent of the rectal ampulla, true rectocele, enterocele, intussusception and anal sphincter trauma were diagnosed offline.

RESULTS

Mean age was 54.1 (range, 17.6-89.7) years and mean body mass index was 29.4 (range, 14.7-67.8) kg/m2 . AI was reported by 149 (13%) patients, with a median St Mark's anal incontinence score of 12 (interquartile range, 1-23). Significant posterior compartment prolapse was seen in 693 (61%) women on clinical examination. Overall, 638 (56%) women had posterior compartment prolapse on imaging: 527 (47%) had a true rectocele, 89 (7.9%) had an enterocele and 26 (2.3%) had an intussusception. Women with ultrasound-diagnosed enterocele had a significantly higher rate of AI (23.6% vs 12.3%; odds ratio (OR), 2.21 (95% CI, 1.31-3.72); P = 0.002), but when adjusted for potential confounders, this association was no longer significant (OR, 1.56 (95% CI, 0.82-2.77); P = 0.134).

CONCLUSION

In women without anal sphincter trauma, posterior compartment prolapse, whether diagnosed clinically or by imaging, was not shown to be associated with AI. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Diagnosis of maternal birth trauma by pelvic floor ultrasound

BRIEF SUMMARY

Maternal somatic birth trauma due to vaginal delivery is more common than generally assumed and an important cause of future morbidity. Maternal birth trauma may involve both psychological and somatic morbidity, some of it long-term and permanent. Somatic birth trauma is now understood to encompass not just episiotomy, perineal tears and obstetric anal sphincter injuries (OASI), but also trauma to the levator ani muscle, termed 'avulsion'. This review will focus on recent developments in the imaging diagnosis of maternal birth trauma, discuss the most important risk factors and strategies for primary and secondary prevention. Translabial and exo-anal ultrasound allow the assessment of maternal birth trauma in routine clinical practice and enable the use of levator avulsion and anal sphincter trauma as key performance indicators of maternity services. This is likely to lead to a greater awareness of maternal birth trauma amongst maternity caregivers and improved outcomes for patients, not the least due to an increasing emphasis on patient autonomy and informed consent in antenatal and intrapartum care.

Underdiagnosis of internal anal sphincter trauma following vaginal delivery

OBJECTIVE

Damage to the anal sphincter during childbirth remains the leading cause of fecal incontinence in women. Defects in the internal (IAS) or external anal sphincter, alongside symptoms and sphincter tone, will generally dictate the suggested mode of delivery in any successive pregnancy. This study aimed to examine using endoanal ultrasonography the prevalence of IAS damage in women referred with Grade-3a or -3b obstetric anal sphincter injury (OASI) in a tertiary-referral perineal clinic.

METHODS

This was a retrospective observational study of all women referred to a tertiary-referral perineal clinic after primary repair of OASI (Grade 3a-c, 4) diagnosed for the first time following vaginal delivery between January 2016 and December 2019, inclusive. Women were assessed using the Wexner bowel continence questionnaire, digital examination of sphincter tone and endoanal ultrasound. Injuries in each sphincter were classified as a scar (≤ 30°) or defect (> 30-90° or > 90°) on endoanal imaging in the axial plane.

RESULTS

In total, 615 women were referred following primary repair of OASI. Sonographic evidence of damage to the IAS was seen in 9.1% (46/506) of women diagnosed with a Grade-3a/3b injury. In women referred with a Grade-3a/3b tear, symptom scores were statistically higher (P = 0.025) in those with an IAS defect > 30° compared to those with an intact or scarred IAS, although the median score was zero in both groups. The proportion of women in each group with severe symptoms (score > 9) was similar (2.6% vs 6.5%; P = 0.148). Among women referred with a Grade-3a/3b tear, sphincter tone was reduced more frequently in those with a defect of the IAS than in those with an intact or scarred IAS (52.2% vs 11.7%; odds ratio, 8.14 (95% CI, 4.26-15.67); P < 0.001). Regardless of the reason for referral, women with reduced sphincter tone on rectal examination were four times as likely to have had an IAS defect > 30° than were those with normal resting tone (risk ratio, 4.58 (95% CI, 3.25-6.45); P < 0.001).

CONCLUSIONS

One in 11 women diagnosed with a Grade-3a or -3b tear have evidence of damage to their IAS on endoanal ultrasound. Damage to this muscle is linked to fecal incontinence in women and can have a significant impact on the planning of any future deliveries. This study highlights the importance of established perineal clinics with access to ultrasound. Nonetheless, if reduced sphincter tone is felt on rectal examination, a clinician should have a high index of suspicion for an occult IAS injury. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.