So called “simultaneous contractions” are the most abundant motor pattern of the human
colon in 24 hr manometry recordings (1), yet we know little about their origin or function, in
part because many suspect them to be artifacts of abdominal pressure changes. This
motor pattern was assessed by High Resolution Manometry (36 sensors, 1 cm apart) in 30 patients with idiopathic constipation or IBS and volunteers to evaluate
their use in assessing neurogenic pathology. “Simultaneous contractions” had a propagation
velocity > 7 cm/s, an amplitude between 5 and 60 mm Hg. They held the colon in a tonic contraction for 10–20 s over the measured 36 cm, often highly rhythmic at 1.5 – 2 cpm. They were by far the most significant motor pattern causing bowel sounds and/or
gas expulsion. A typical “simultaneous contraction” was associated with many haustral
boundary contractions. When the internal anal sphincter pressure was recorded at the
same time, relaxation was observed in synchrony with the “simultaneous contractions”,
even if they were of very low amplitude (<5 mm Hg) indicating that it was not rectal contraction or distention but a neural program
that induced IAS relaxation. We believe the simultaneous contractions to be the motor
equivalent of electrical activity termed “rushes” with a velocity of 10.5 ± 2.6 cm/s (2). Hence “simultaneous contractions” are fast propagating contractions orchestrated
by a neural program that includes anal sphincter relaxation. Its rhythm may be linked
to neurally induced pacemaker activity of the intramuscular interstitial cells of
Cajal. Supported by grants from the National Natural Science Foundation of China and
the Canadian Institutes of Health Research.
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© 2015 Published by Elsevier Inc.