Anal sphincter disruption during instrumental and non-instrumental vaginal delivery

Introduction: Anal sphincter trauma during childbirth represents the most important risk factor for development of fecal incontinence in women. Overt anal sphincter injury may be identified by clinical examination in 1-3% of vaginal deliveries, but the incidence is much higher when abnormalities are specifically sought using endoanal ultrasound and anal manometry.
Aim of work: The aim of this study is to assess risk factors for sphincter damage during vaginal delivery in primiparous patients, and to assess the relationship of anal manometry and endosonography to anorectal complaints in patients who had demonstrated anal sphincter injury during vaginal delivery.
Patients & methods: This was a prospective, observational study conducted over 130 healthy primiparous females with intact anal sphincter without history of either anorectal complaints or previous anorectal surgery.   The patients were divided into: Group I: 100 patients without clinically recognized third- to fourth-degree intrapartum perineal tears. Group II: 15 primiparous patients who delivered by normal vaginal delivery, with clinically recognized third-degree perineal tears, who were examined following surgical repair by the overlapping technique. Group III: 15 primiparous patients who delivered by instrumental delivery, with clinically recognized third-degree perineal tears, who were examined following surgical repair. All patients were  followed  up  by  combined  endoanal  ultrasonography  and  anal  manometry.
Results: The risk factors for the anal sphincter damage during vaginal delivery include the length of 2nd stage if •75 min, absence of episiotomy, presence of shoulder dystocia, and the mode of delivery. In patients with anal sphincter damage, the maximal anal resting pressure (MARP) was significantly lower (P<0.001) in patients with anorectal complaints than in those without complaints, but maximal anal squeeze pressure (MASP) was not different between groups (P>0.05). Instrumental delivery (P<0.001), a MARP •30 mmHg (P<0.047), and ultrasound evidence of combined ES + IS defect (P=0.002), were significantly related to anorectal complaints. MASP and ultrasound evidence of an isolated EAS defect were not found to be significantly related to anorectal complaints.
Conclusion: Knowledge of possible risk factors for the occurrence of anal sphincter injuries may therefore reduce the likelihood of faecal incontinence. Anal endosonography after vaginal delivery allows the diagnosis of clinically undetected anal sphincter damage that may be associated with subsequent fecal incontinence. Anal monometry is useful in assessment of anal sphincter disruption following vaginal delivery especially when combined with an endoanal ultrasonography