Objective: The anatomy of the anal canal, the anorectal junction and the lower rectum was studied with 3-D ultrasound.
Method: Seventeen women with normal bowel transit, without rectocele (group 1) and 17 female patients with a large anterior rectocele (group 2) were examined with a B&K Medical Rawk. Mean age was 44.5 and 51.6 years respectively. In group 1, one (5.8%) patient was nuliparous, five (29.4%) had a caesarian section, 11 (64.7%) had a vaginal delivery while in group 2, two (11.7%) patients were nuliparous, four (23.5%) had a caesarian section and 11 (64.7%) had a vaginal delivery. Images were reconstructed in midline longitudinal (ML) and transverse (T) planes. The external (EAS) and internal (IAS) anal sphincters were measured in both projections.
Results: In the ML plane, the EAS length was longer in group 1 (1.94 cm vs 1.61 cm, P < 0.05), the gap length was shorter (1.54 cm vs 1.0 cm P < 0.01) and the wall thickness was shorter in group 2 (0.40 cm vs 0.50 cm P < 0.01). The IAS (0.18 cm vs 0.23 cm P < 0.01) and EAS thickness (0.68 cm vs 0.77 cm, P < 0.05) (left lateral of the posterior quadrant) was greater in group 2. In group 1, the anterior upper anal canal wall in normal females was an extension of the rectal wall and the circular muscle was thicker in the mid-anal canal to form the IAS. In group 2, however, the wall layers were not identified and the IAS was found to be more distal. The differences were not statistically significant in the anal canal resting and squeeze pressures in the two groups.
Conclusion: Obstetric trauma does not seem to play any role in rectocele pathogenesis because the anal sphincter muscles are anatomically and functionally normal and rectocele is also present in nuliparous and in women with caesarian sections. It seems that it is associated with the absence of EAS and thinner IAS in the anterior upper anal canal. Herniation starts at the upper anal canal extending to the lower rectum in high or large rectoceles and maybe produced by rectal intussusception because of excessive and prolonged straining during defecation. In fact, the denomination 'rectocele' should be changed to 'anorectocele'.