We have previously demonstrated that the
rectosigmoid junction is more than a junction: it is a segment
with a mean length of 2.8 cm which we termed the
'rectosigmoid canal' (RSC). Our data support the existence
of a physiologic and anatomic sphincter at the RSC which
regulates the passage of stools from the sigmoid colon (SC)
to the rectum (R). In view of its sphincteric action we
investigated the hypothesis that the RSC has a higher electric
activity than that of the SC and R. The tests were performed
during repair of huge incisional hernia in II subjects (age
46.7±12.5 years; 8 women). The electric activity was
recorded by means of 2 monopolar electrodes applied to each
of the SC, RSC and R. The RSC was then anesthetized with
xylocaine and the electric activity of SC. RSC and R was
recorded after 10 minutes and one hour. The test was
repeated using saline instead of xylocaine. The SC, RSC and
R exhibited electric activity in the form of pacesetter
potentials (PPs) and action potentials (APs). The PPs were
monophasic in the SC and triphasic in the RSC and R. The
frequency, amplitude and conduction velocity of the waves
recorded from the RSC and R had higher readings (p<0.05)
than those from the SC. The RSC and R showed a similar
frequency and conduction velocity, but the RSC had a higher
amplitude (p<0.05). Ten minutes after RSC anesthetization.
electric waves were recorded from the SC but not from the
RSC or R; electric activity returned one hour after
anesthetization. Saline injection of the RSC did not affect the
electric activity of the RSC. SC or R. The electric wave
pattern and parameters of the RSC and R differed from those
of the SC, suggesting that they are evoked by 2 different
pacemakers. The similarity in pattern, frequency and
conduction velocity of electric waves of RSC and R supposedly denotes that the rectal waves are a continuation
of those of the RSC and that both are evoked by a single
pacemaker located in the RSC. The higher amplitude of the
RSC waves may be due to the thicker RSC musculosa in
comparison to that of the SC and R and may by itself be an
evidence of the sphincteric function of the RSC. |
