Comparison of diagnostic criteria for significant anal sphincter defects between endoanal and transperineal ultrasound

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.

Quality assessment of transperineal ultrasound in Chinese tertiary medical centers: a multicenter study

Background

Transperineal ultrasound (TPUS) is a vital examination method for diagnosing pelvic floor diseases. However, the quality of TPUS largely relies on the operator's experience, and there is a lack of studies on the evaluation of TPUS quality. Therefore, the objective of this study was to assess the quality of TPUS examinations in Chinese tertiary medical centers.

Methods

This multicenter study conducted in 44 Chinese tertiary medical centers recruited postpartum women between September 2020 and September 2021. All participants underwent a standardized inquiry and TPUS examination. The participating centers were required to submit 5 parts of ultrasound data to the National Ultrasound Quality Control Center: 2-dimensional images at rest, 2-dimensional images at strain; 4-dimensional images of the levator ani hiatus; 4-dimensional images of the levator ani muscle; and 4-dimensional images of the anal sphincter. Quality assessment was performed by 2 experts with more than 5 years of experience in TPUS, and the reasons for nonqualification were stated.

Results

In this study, 31 hospitals that were distributed across 20 provinces in China were included, submitting 2,251 cases in total. The overall qualified rate ranged from 12.00% to 86.92%. In each part, the qualified rate of 2-dimensional images at rest, 2-dimensional images at straining, levator ani hiatus, levator ani muscle, and anal sphincter was 94.27% (2,122/2,251), 78.54% (1,768/2,251), 85.52% (1,925/2,251), 93.03% (2,094/2,251), and 88.09% (1,983/2,251), respectively. Most of the nonqualified images belonged to 2-dimensional images at strain, and the errors in image acquisition (221/483, 45.76%) and measurement (262/483, 54.24%) were the main reasons for nonqualification. For levator ani hiatus images, error in image acquisition (275/326, 84.36%) was the main reason for nonqualification. Reconstruction error was the most common reason for nonqualification for levator ani muscle (133/157, 84.71%) and anal sphincter images (133/268, 49.63%).

Conclusions

This multicenter study assessed the quality of TPUS in tertiary medical centers in China and identified the common reasons for nonqualification in each part. These findings can aid in forming the basis for quality control management and training for TPUS.

Assessing Obstetric Anal Sphincter Injuries: A Comparison of Exoanal and Endoanal Ultrasound

OBJECTIVES

To explore the differences in assessing obstetric anal sphincter injuries (OASI) between transperineal ultrasound (TPUS) and endoanal ultrasound (EAUS) and test relationships between ultrasound findings and anal incontinence (AI) symptoms.

METHODS

A group of 196 women with a history of vaginal delivery was recruited. OASI was detected in a set of 5 slices by EAUS and 8 slices by TPUS. OASI grading was performed on TPUS rules and EAUS rules. A "significant sphincter defect" was diagnosed by TPUS and EAUS using "2/3 rules." Symptoms of AI were determined using the St Mark's Incontinence Score (SMIS). Ultrasound findings were compared between the two methods and correlated with symptoms.

RESULTS

Of 196 women, 29 (14.8%) suffered from AI with a mean SMIS of 12.1 ± 4.5, and 70 (35.7%) women with a mean age of 57 years had suspected OASI on imaging. Twenty-one (10.7%) "significant defects" were diagnosed by TPUS and 24 (12.2%) by EAUS. OASI Grades on TPUS had good agreement with EAUS rules (k = 0.70, P < .001). Logistic regression analysis showed that OASI Grade on imaging and "significant sphincter defects" seen on both forms of imaging were associated with AI symptoms. The odds ratio was 46 and 38 for "significant defects" on TPUS and EAUS, and 14 and 7 for OASI 3b+ on TPUS and EAUS in predicting AI, respectively.

CONCLUSIONS

"Significant defects" diagnosed by EAUS or TPUS and OASI Grade 3b+ predict AI symptoms. The diagnostic performance of endoanal and exoanal ultrasound (EAUS and TPUS) appear to be very similar.

Morphological differences in the female anal sphincter complex between endoanal and exoanal ultrasound

INTRODUCTION AND HYPOTHESIS

This study was aimed at describing the morphological characteristics of the normal female anal sphincter complex (ASC) by high-resolution transperineal ultrasound (TPUS) and endoanal ultrasound (EAUS).

METHODS

Thirty volunteers, including 19 nulliparous and 11 women who had only given birth by Cesarean section, were recruited. The ASC was shown in a set of five slices by EAUS and 8 slices by TPUS. EAUS slices 1 and 5 matched TPUS slices 1 and 8; EAUS slices 2, 3, and 4 were approximately at the levels of TPUS slices 3, 5, and 7. The anterior and lateral EAS and IAS thicknesses were measured and the two methods were compared.

RESULTS

The median age was 29 years. The mean body mass index (BMI) was 20.6 kg/m². All measured values obtained by TPUS were normally distributed. The EAS thickness on EAUS slice 2 and the IAS thickness on EAUS slices 2 and 3 were not normally distributed. The mean anterior EAS thickness was 2.51 mm, 2.96 mm, and 3.53 mm in slices 3, 5, and 7 on TPUS and was significantly thinner than that in slices 2 (2.62 mm), 3 (3.77 mm), and 4 (4.62 mm) on EAUS. In contrast, the IAS was markedly thicker on TPUS. The ratio of sphincter thickness anteriorly to laterally was similar using the two methods.

CONCLUSIONS

The morphological characteristics of EAS shown by TPUS and EAUS were similar. EAS was thinner, and IAS was thicker on TPUS. The IAS seems to be distorted on endoanal imaging.

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.