A simple method for the correction of biliary excretion curves distorted by the biliary dead space

Biliary solute concentrations measured at the tip of the cannula suffer a delay with respect to bile flow due to the transit time through the biliary tree volume. This study proposes a simple method, which is valid under variable bile flow conditions, to correct the distortion introduced by the biliary tree volume on the kinetic curves of the biliary excretion rate. The biliary transit time (tt) was calculated as the time needed to excrete a bile volume equal to the biliary tree volume by means of the interpolation of biliary cumulative volume versus time curves. Such tt permits one to estimate the canalicular concentration at time t, interpolating the biliary concentration curves at time t-tt. The product between the estimated canalicular concentration and the bile flow allows the calculation of the corrected biliary excretion rate. This method was evaluated by a comparison between biliary excretion rate curves of [14C]taurocholate [( 14C]TC) injected as a bolus under basal and sodium dehydrocholate (DHC)-induced choleresis conditions. Since the canalicular excretion rate of [14C]TC is considered independent of bile flow, the significant differences observed in its excretion kinetics under both conditions were attributed to distortion due to the biliary tree volume. After the correction, both curves showed a significant overlapping. This result indicates that the method improves the time-course representation of canalicular events in biliary excretion kinetic studies.