Maximal biliary transport of sulfobromophthalein in patients with a T-tube placed in the common bile duct

In 19 adult patients with choledocholithiasis who were operated on, excretion of free and conjugated sulfobromophthalein (BSP) in the bile collected through a T-tube inserted in the common bile duct was determined. The transport maximum (Tm) for BSP was calculated by the constant-infusion technique after an intravenous infusion of the dye at a rate of 0.3 and 0.09 mg/kg/min for the first and second hour, respectively. Free and conjugated BSP were measured in blood samples obtained at 30, 40, and 50 min of each hourly-infusion period, and in bile collected during the first 30 min (sample A) and between 30–50 min (sample B) after starting the first BSP infusion, and during the first 30 min (sample C) and between 30–50 min (sample B) after starting the second infusion. No correlations between Tm of BSP and glutathione transferase activity and between Tm and bilirubin and alkaline phosphatase in serum were found. Although there was an overall correlation between Tm of BSP and biliary excretion of BSP after 30 min of starting the BSP infusion (samples B, C and D) (r=0.4716;P=0.41), Tm values were always lower than recoveries of free BSP in bile. It seems that Tm of BSP (measured with the Wheeler’s method) overestimates the actual values of biliary excretion of free BSP, and that the percentage of conjugated BSP in serum is related to the degree of impairment of biliary transport of BSP.