Does exclusion of subcutaneous external anal sphincter on exoanal imaging matter?

Diagnostic capabilities of transperineal ultrasound (TPUS) to evaluate anal sphincter defect post obstetric anal sphincter injury (OASIS)? A systematic review

INTRODUCTION

Endoanal ultrasound (3D-EAUS) is the gold standard imaging investigation for evaluating the anal sphincter; unfortunately, it is not universally available in most obstetric units. This study aims to appraise the ability of transperineal ultrasound (TPUS) compared with 3D-EAUS as the gold standard to identify anal sphincter defects after primary repair of OASIS.

METHODS

A systematic search of major databases to identify diagnostic accuracy of 3D-TPUS in evaluating anal sphincter defects. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were designed for this systematic review. The risk of bias and applicability concerns were assessed using the QUADAS-2 tool. Our eligibility criteria are patients with a history of primary repair of anal sphincter injuries (OASIS). They were followed up after the primary repair to detect the anal sphincter defect using 3D-TPUS vs. 3D-EAUS as a gold standard.

RESULTS

Two eligible observational studies were included and assessed for risk of bias using the QUADAS-2 tool and showed a low risk of bias and a low risk of concerns. 3D-TPUS had various sensitivity to detect external anal sphincter defects in two studies; meanwhile, the specificity was around 67-70%. For detecting the internal anal sphincter defects, 3D-TPUS had low sensitivity but high specificity (93-94%).

CONCLUSION

3D-TPUS had various sensitivity to detect external anal sphincter defects and low sensitivity to detect internal anal sphincter defects. On the other hand, 3D-TPUS had low specificity for detecting external anal sphincter defects and high specificity for detecting internal anal sphincter defects.

Location of obstetric anal sphincter injury scars on translabial tomographic ultrasound

OBJECTIVE

Obstetric anal sphincter injury (OASI) is a common preventable cause of anal incontinence. Both diagnosis and primary repair of OASI are often suboptimal, partly owing to the absence of effective clinical audit. The aim of this study was to evaluate the location of scars or defects of the external anal sphincter (EAS), diagnosed by translabial ultrasound (TLUS), following primary OASI repair.

METHODS

This was a retrospective analysis of 309 women who were seen at a tertiary obstetric unit after primary repair of OASI between June 2012 and May 2019. All women underwent a standardized interview, including St Mark's incontinence score, followed by clinical examination and TLUS assessment within 2-9 months after OASI repair. Postprocessing of TLUS volume datasets was performed by an investigator who was blinded to all other information. Tomographic ultrasound imaging was used to evaluate the presence of a scar or defect in the proximal and distal parts of the EAS. Women were classified into four groups according to the imaging findings: (1) no visible defect or distortion (likely false positive); (2) only proximal OASI; (3) only distal OASI; and (4) both proximal and distal OASI.

RESULTS

Of the 309 women seen during the study period, 34 were excluded because they were referred for reasons other than recent (< 1 year) OASI, 16 owing to missing data and four owing to poor image quality, leaving 255 patients for analysis. Women were seen on average 0.25 ± 0.1 years after the index birth, and their mean age at delivery was 29.1 ± 4.6 years. Anal incontinence was reported by 97 (38.0%) women. A scar or defect was seen only in the proximal part of the EAS in 64 (25.1%) women and only in the distal part in 19 (7.5%) (P < 0.001). In 165 (64.7%) women, the damage affected both the proximal and distal EAS.

CONCLUSIONS

EAS scars after primary OASI repair commonly affect the entire length of the EAS; however, partial tears seem to be more likely to occur proximally. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

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.