Dynamic MRI of the pelvic floor muscles in an upright sitting position

Since the pelvic floor muscles are situated inside the pelvis, the actual f unction is difficult to observe. Magnetic resonance imaging (MRI) is a new method that may prove to give additional information about pelvic floor mus cle function during contraction. The purpose of the present study was to as sess pelvic floor muscle function during contraction and straining in an up right sitting position by use of MRI. Sixteen women, nine continent and sev en with urodynamically and clinically proven genuine stress incontinence pa rticipated in the study. MRI was performed in an open-configured GE Signa S P. 0.5 T Tesla magnet. With the participants sitting in an upright position on a pelvic RF-coil, sagittal, coronal and axial T1 weighted spin echo ima ges of the pelvic floor were obtained. During contraction and straining a s can rime of 2 seconds per image for 150-250 images, was performed in a mid- sagittal plane. The results showed that the mean inward lift during contrac tion was 10.8 mm (SD 6.0) for all women. During straining the mean downward movement was 19.1 mm (SD 7.4). The coccyx moved in a ventral, cranial dire ction during contraction and was pressed in a caudal, dorsal direction duri ng straining. It is concluded that contraction of the pelvic floor muscles is concentric, moving the coccyx in a ventral, cranial direction. The movem ent measured by MRI in upright sitting position is less than that concluded after clinical observation in supine position. The coccyx is pressed dorsa lly during straining. (C) 2001 Wiley-Liss, Inc.