Comparative Study of Anatomic and Physiologic Measurement of the Anal Sphincter in Adult Women

ABSTRACT

PURPOSE: This study has carried out to clarify the relationship between changes in the anal sphincter muscle thickness and pressure. Also, this study shows the effect of vaginal delivery and benign anal disease on the function and structure of the anal sphincter. METHODS: Women (n=42; mean age 33.2 +/- 9.6 years old) without defecation problems or history of anal surgery, who came to Ewha Womans University Hospital between July 1999 and October 1999, were chosen. We measured the resting and the squeezing pressure with anal manometry and the thickness of the internal anal sphincter (IAS) and external anal sphincter (EAS) by endoanal sonography. RESULTS: The mean squeezing and resting pressures were 98.3 +/- 38.2 and 53.9 +/-17.4 cmH2O, and the mean EAS and IAS thicknesses were 4.9+/-0.9 and 1.9+/-0.3 mm, respectively. The thickness of the EAS and squeezing pressure did not correlate. Neither did the IAS thickness and the resting pressure. In cases with a history of vaginal delivery (n=15), the squeezing and the resting pressures were 94.0+/-43.0 and 57.1+/-22.2 cmH2O, and the thicknesses of the EAS and the IAS, 4.6+/-0.9 and 2.0+/-0.4 mm, respectively. The number of deliveries had no correlation with the thickness or the pressure of the anal sphincter. In patients with benign anal lesions (n=11), the squeezing and the resting pressure was 113.0+/-42.9 and 57.0+/-14.0 cmH2O, and the thicknesses of the EAS and the IAS were 5.0+/-1.3 and 2.1+/-0.4 mm, respectively. CONCLUSION: Our data suggest that the function and the structure of the anal sphincter are independent. In adult women, the thickness of the anal sphincter, the history of vaginal delivery, and the existence of benign anal lesions had no effect on anal sphincter function.