Magnetic resonance imaging pelvimetry in 186 patients with rectal cancer confirms an overlap in pelvic size between males and females

Introduction It has generally been considered that open pelvic surgery is almost always easier in female subjects because of anatomical differences facilitating surgical access. In contrast, the male pelvis has been considered to be narrower and deeper. The objective of this study was to assess magnetic resonance imaging (MRI) pelvimetry in patients with rectal cancer in whom any difference in pelvimetry may potentially affect operative management. Male and female pelvic bony dimensions were compared. Method A cohort of 186 patients (112 males and 74 females) with rectal cancer who had been recruited prospectively to the Magnetic Resonance Imaging and Rectal Cancer European Equivalence Study (MERCURY Study) were assessed. Complete digital images were available on these patients. A comparison of the pelvic dimensions was made between the sexes using 16 dimensions measured on the MRI workstation using the mid-sagittal and axial images. Results There was no significant difference and considerable overlap between the sexes with respect to each of the 14 parameters measured from the preoperative sagittal MRI scan. However, there was a highly significant difference between the interspinous and intertuberous transverse diameter of the pelvis (P < 0.0001). Conclusion Outcome after surgery may be influenced by the technical difficulty of the operation and this had been thought to be partly affected by the pelvic size. In this cohort of 186 patients, the only difference seen between the sexes, was in the transverse mid-inlet and pelvic outlet diameter.