Feasibility of transperineal ultrasound in the delivery room for the management of obstetric anal sphincter injuries: a randomized controlled trial

: Obstetric anal sphincter injury (OASI) is one of the major complications of vaginal delivery. Several lesions remain clinically undiagnosed at delivery. The objective of this study was to evaluate the feasibility and impact of performing a transperineal ultrasound (TPUS) in the immediate postpartum period by a non-expert obstetrician. : We conducted a prospective bicentric randomized controlled trial comparing clinical examination alone (CE group) versus clinical examination associated with transperineal ultrasound (TPUS group), in primiparous women following a vaginal birth with ≥ second degree perineal tear or episiotomy. If a 3 rd or 4 th degree perineal tear was diagnosed clinically and/or by TPUS, an OASI repair was performed. Patient tolerance was assessed using a visual analogue scale (VAS), and associated complications were recorded. The primary outcome was anal incontinence at 5 months postpartum, evaluated using the Wexner scale. All TPUS images were independently reviewed by an expert gastroenterologist (expert) to assess the inter-observer agreement. : A total of 110 nulliparous women were enrolled, 54 in the CE group and 56 in the TPUS group. Of these, 51 and 47, respectively, completed the 5-month follow-up. The rate of operative vaginal delivery was 44% (49/110), mainly using spatulas (42/49), and 57% (63/110) of women had a mediolateral episiotomy. The rate of severe perineal tears diagnosed by clinical examination alone was 12.7% (14/110) (9, 3, 0, and 2 patients had 3a, 3b, 3c, and fourth-degree tears, respectively). Transperineal ultrasound was performed in all patients randomized to the TPUS group. Among 51 patients diagnosed with a second-degree tear on clinical examination, TPUS revealed four (7.8%) occult OASIs (three 3a and one 3c tears). Tolerance to TPUS was good, with a mean VAS score of 0.43 (±1.33), which was lower than that for clinical examination. The rate of anal incontinence at 5 months postpartum (Wexner score >4) was lower in the TPUS group (1/47, 2.1%) than in the CE group (4/51, 7.8%), but this difference was not statistically significant (p=0.19). Inter-observer agreement between the obstetrician and the expert was poor for identifying both external (κ=0.259) and internal (κ=0.367) anal sphincter lesions on TPUS. : Improving the diagnosis and prognosis of OASI at the time of delivery using transperineal ultrasound combined with clinical rectal examination is feasible when performed by a non-expert obstetrician and is well tolerated by women. However, it requires specific ultrasound equipment, which is not always available, and inter-observer agreement with expert assessment remains poor for both external and internal anal sphincter lesions.