RELATIONSHIP BETWEEN INTRAABDOMINAL AND INTRARECTAL PRESSURE IN THE PROCTOMETROGRAM

During normal defaecation the intrarectal pressure increases but, in t he absence of a reference catheter in the pelvis, the contribution of abdominal straining and rectal contraction to this rise is unclear. An orectal manometry was performed in ten consecutive women with no gastr ointestinal symptoms in an attempt to measure intrapelvic pressure usi ng a catheter in the bladder. During filling the mean(s.e.m.) rectal p ressure increased from 2(1) to 18(4) cmH2O. The mean(s.e.m.) intravesi cal pressure remained unchanged at 2(1) cmH2O. Evacuation of the recta l balloon produced an increase in mean(s.e.m.) intrarectal pressure fr om 18(4) (end-filling pressure) to 68(15) cmH2O. The mean(s.e.m.) intr avesical pressure increased from 2(l) to 51(18) cmH2O. The true intrar ectal pressure (intrarectal minus intravesical) did not rise during de faecation. The rise in intrarectal pressure during rectal evacuation o ccurs by increased intrapelvic pressure alone.