Retrospective analysis of 3a obstetric anal sphincter injury repairs in a teaching hospital: Subjective and objective outcomes

Introduction

The Royal College of Obstetricians and Gynaecologists (RCOG) recommends offering elective caesarean sections (CS) for subsequent deliveries to obstetric anal sphincter injury (OASI) patients with anorectal dysfunction, or abnormal endoanal ultrasonography (EA USS), and/or anal manometry (AM). (1) Asymptomatic OASI patients however, are not always offered EA USS or AM due to limited access to diagnostic resources across the United Kingdom, particularly those with 3a tears. This paper reviews subjective and objective outcomes in women with 3a tears and aims to add to the body of literature supporting good practice and management.

Objectives

Identify the incidence of defects in patients with 3a tears following a primary repair and compare the rate and extent of defects found on EA USS between symptomatic and asymptomatic women.

Study Design

We performed a retrospective study of 69 women following primary repair of 3a OASI tears in a tertiary referral perineal clinic between January 2020 and December 2022. Symptoms were evaluated using the St Mark’s Score for anal incontinence (SMI) and Starck score for defects on EA USS. Findings were analyzed using R Foundation Statistical Software (version 4.2.2, 2022).

Results

Out of the total, 42 % (29/69) had defects on EA USS and 30 % (21/69) of women were symptomatic. Thirty eight percent (18/48) of asymptomatic women were noted to have defects compared with 52 % (11/21) of symptomatic patients. Majority of defects were situated in the upper and mid anal canal (69 %) either as <1 hr or >3 hr hypoechoic areas. There was no significant difference in defect rate (X² = 2.06, p = 0.15) or Starck score (2.23 v 1.53, p = 0.22) between the two groups. However those delivered by forceps (p = 0.004) and of Asian ethnicity (p = 0.01) were more likely to be symptomatic.

Conclusion

EA USS should be offered to all patients following an OASI, as symptoms alone are not predictive of anorectal compromise in structure and/or function. Asymptomatic patients with 3a tears should be informed that there is up to a 40% chance of finding a defect on EA USS.