Response of canine ileocolonic sphincter to intraluminal acetic acid and colonic distension

The aim was to determine the effect of intraluminal acetic acid and proximal colonic distension on canine ileocolonic sphincter pressure, ileal motility, and coloileal reflux. In six conscious dogs with an isolated ileocolonic loop, basal pressure of the ileocolonic sphincter was similar during ileal perfusion with 100 mM acetic acid at 1 ml/min (mean±sem=18±0.4 mm Hg) and with saline (18±0.5 mm Hg;P=0.81). Discrete clustered ileal contractions were more frequent with acetic acid, however, and when they propagated across the sphincter, sphincter pressure increased from 18±0.4 mm Hg to 36±1.3 mm Hg (P=0.002). Sphincter pressure was also greater during colonic perfusion with acetic acid (32±0.7 mm Hg) than during ileal perfusion with acetic acid or saline (P<0.017). Moreover, sphincter pressure gradually increased as the colon was distended with saline (slope=0.8 mm Hg/cm H₂O,P<0.017) or acetic acid (slope=0.5 mm Hg/cm H₂O,P<0.017), but the increase did not prevent coloileal reflux. In conclusion, ileal clustered contractions, colonic perfusion of acetic acid, and colonic distension all increased canine ileocolonic sphincter pressure.