Patients with acromegaly have an increased risk of developing colorectal cancer and a significantly higher prevalence of tubulovillous adenomas compared with normal subjects. Routine surveillance colonoscopy is indicated in this group of patients.

SUMMARY1. Bromsulphthalein (BSP) was administered throughout the experiments at a constant rate well in excess of its excretory rate, to anaesthetized dogs in which the common bile duct had been cannulated. The maximal excretory rate of BSP into bile (BSP Tm) obtained in this manner was greatly elevated by choleresis arising from the administration of bile salt (usually taurocholate) at constant rate.2. When bile flow rate was increased in stages by raising the taurocholate administration rate, successive increments in BSP excretion rate were obtained up to a limiting value of about 3 times the original Tm. Beyond this point further increases in taurocholate administration rate caused either no further enhancement of BSP Tm or a decline in the extent of enhancement produced at a previous lower rate of infusion.3. When taurocholate maximal secretion was established first, the subsequent administration of BSP at progressively increasing rates led to reduction in the taurocholate secretion rate.4. Portal infusion of secretin at constant rate (usually 0x2 units/kg body wt. min) which caused substantial increases in bile flow rate, had no effect on BSP Tm. Increases of bile flow rate of the same order following constant taurocholate infusion produced marked elevation of the BSP Tm.5. These findings are discussed and the following conclusions reached: (a) The limiting factor in BSP maximal transfer is the concentration of BSP in bile; increased bile flow rate at the site of BSP excretion (canaliculi) produced by bile salt administration permits an increase in the original Tm to occur without the limiting biliary concentration being exceeded.(b) There is excretory competition between BSP and bile salt but over a certain range of bile salt administration the facilitatory effects of increased bile flow rate outweigh the inhibitory effects due to competition. BILIARY TRANSPORT MAXIMA (c) Since secretin administration had no effect on BSP Tm, it is likely that the hydrocholeresis it produces originates downstream from the canaliculi, i.e. in the bile ductules or ducts; this supports previous evidence obtained in a different manner.

SUMMARY1. Sodium taurocholate or cholate was administered systemically at a constant rate of about 2-9 #mole/min.kg body wt. to anaesthetized dogs in which the common bile duct had been cannulated. In steady-state conditions blood was sampled from systemic and hepatic veins and the fraction of bile salt removed in a single passage through the liver was determined. Total hepatic blood flow was estimated by application of the Fick principle.2. The hepatic extraction fraction for synthetic taurocholate in ten experiments was 92 % ± 5 % (S.D.) over the blood flow range encountered (1.1-2.8 ml./min.g liver). The extraction of cholate extensively conjugated in the liver before excretion into bile was 79 % ± 8 % (S.D.)(twenty-one observations, thirteen experiments). In circumstances of similar hepatic blood flow the extraction of cholate transferred to bile in the free form (after acute taurine depletion) was significantly less than that of either synthetic taurocholate or cholate which could be actively conjugated before excretion. These results, which are discussed and criticized, support previous work on the advantage of conjugation in the transfer of cholic acid from blood to bile. 3. The hepatic clearance ofbile salt decreases with increasing administration rate, but the values obtained may be influenced by changes in hepatic blood flow. With regard to taurocholate an increase in total hepatic flow was observed when its administration rate exceeded about 5 ,umole/min . kg body wt.4. The secretory maximum for glycocholate, a bile salt not normally found in dog bile, was of the same order as that for taurocholate.

1. A method is described for the measurement of liver blood flow without hepatic venous catheterization by the injection of the a single dose of bromosulphthalein and the analysis of the graph of the plasma disappearance of the indicator. 2. The rationale of the method was tested in three systems which covered a wide range of flow rates. The first system was a physical model with a haemodialyser in which the calculated flow could be compared with the flow measured directly. The second was in anesthetized dogs, in which the calculated flow was compared with that measured by continuous infusion and hepatic venous catheterization, based on the Fick principle. The third system was in unanaesthetized turkeys, in which metabolism of bromosulphthalein does not occur. The calculated flow was compared with the flow measured simultaneously by the uptake of collodial particles by the Kupffer cells. 3. In all three systems the correspondence between the two methods of measuring liver blood flow was good, the differences between them being not statistically significant. 4. The method has been applied to measurements of liver blood flow in man and animals and gives results comparable with those reported by other workers.