Dynamic 2-dimensional transperineal ultrasound evaluation in labor room as a screening tool for anal sphincter injuries and anal incontinence in primiparous women

Background: Early repair of obstetric anal sphincter injuries is crucial in the prevention of anal incontinence, but the diagnostic accuracy of the clinical examination after delivery is poor. Endoanal ultrasound imaging is now regarded as the gold standard for diagnosing anal sphincter injuries, and it improves the diagnosis of these lacerations. Four-dimensional transperineal ultrasound imaging has been proposed as an effective and less invasive alternative to endoanal ultrasound imaging in the diagnosis of anal sphincter injuries. Objective: The purpose of this study was to evaluate the feasibility and accuracy of the assessment of anal sphincter contraction by dynamic 2-dimensional transperineal ultrasound imaging immediately after delivery and its correlation with anal incontinence at the 4-month follow-up evaluation. Study Design: A nonconsecutive series of nulliparous women with low-risk singleton term pregnancies were recruited in the labor room after vaginal delivery for the purpose of this study from January 2017 to July 2017. All enrolled patients had a clinical examination of the perineum by the caregiver that was repeated by an experienced research fellow. For each patient, a further dynamic 2-dimensional transperineal ultrasound imaging were carried out. Before the perineal repair, the women were asked to contract the anal sphincter during 2-dimensional transperineal ultrasound imaging; they were divided in 2 groups according to the sonographic findings: women with sonographic evidence of anal sphincter contraction (group A) and women with no evidence of contraction at ultrasound imaging (group B). A follow-up examination of anal sphincter integrity with 4-dimensional transperineal ultrasound imaging was carried out 4 months after delivery. At this time, the levator ani integrity was evaluated with the use of 4-dimensional transperineal ultrasound imaging, as previously described. Results: Over the study period 69 women were enrolled. In 55 women (80%), there was evidence of proper anal sphincter contraction (group A); in 14 cases (20%), it was not possible to identify anal sphincter contraction with dynamic 2-dimensional transperineal ultrasound imaging (group B). Obstetric anal sphincter injuries that were detected through clinical examination were significantly more frequent in group B than in group A (13/14 [93%] vs 7/55 [12%]; P<.001). At the 4-month postpartum follow up, the previously recognized obstetric anal sphincter injuries were found to be repaired correctly; a third-degree perineal tear that had not been reported previously was diagnosed by 4-dimensional transperineal ultrasound imaging . Anal incontinence was reported in 8 of 69 patients (11%); it was more frequent in group B when compared with group A (4/14 [29%] vs 4/55 [7%]; P=.047). Conclusion: Dynamic 2-dimensional transperineal ultrasound imaging is a feasible technique and a useful supporting tool for the assessment of anal sphincter integrity in the labor room before suturing. Anal incontinence at the 4-month follow-up evaluation is more frequent among women with no evidence of anal sphincter contraction at dynamic 2-dimensional transperineal ultrasound imaging after delivery.