Subclinical anal sphincter injuries following instrumental delivery-a physiological analysis: A pilot study

Introduction: Obstetric Anal Sphincter Injuries (OASIS) has been reported in up to 25% patients and occult OASIS has been reported in up to 1.2%. Instrumental delivery has been considered a risk factor for OASIS. Aim: To compare the anal sphincter functions as assessed by Anorectal Manometry (ARM) in asymptomatic patients following instrument delivery with those of patients who underwent Lower Segment Caesarian Section (LSCS) after six months of delivery. Materials and Methods: Seventeen women who had instrumental delivery and thirteen who underwent elective cesarean section were recruited. Evaluation included a detailed history and physical examination, administration of the Cleveland Clinic Questionnaire and ARM to record the basal pressure, squeeze pressure, anorectal sensation and balloon expulsion time. Categorical variables were compared using the Chi-square test. All calculations were done using the software SPSS 21.0. Results: We found statistically significant lower basal (34±3.4 vs 60±2.3 mm hg, p<0.05) and squeeze pressures (56±4.1 vs 76±5.2 mm hg, p<0.05), and higher balloon expulsion time (58±2.9 s vs 19±1.8 seconds, p<0.05) in women with instrument delivery compared to LSCS. The rectal sensation was comparable in both the groups. Conclusion: Persistent subtle anal sphincter dysfunctions are common following instrument delivery compared to LSCS. The role of identifying these and preventing future incontinence in such women needs to be assessed in future studies.