Noninvasive Measurement of Nutrient Portal Blood Shunting: An Experimental Study With [14C]Ursodeoxyeholie Acid

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Abstract
All of the methods proposed for measuring portal blood flow are either invasive, estimate total rather than nutrient flow, and none has proved reliable in cirrhotic patients. A method has been derived from pharmacokinetic principles used for the calculation of bioavailability of drugs according to the route of administration (i.v. or p.o.) and tested experimentally in 20 pigs. A tracer dose of [14C]ursodeoxycholic acid, a biliary acid with a high–liver first–pass effect, is administered in the duodenum, and serial peripheral blood samples are taken. Later, the same dose of the same drug is administered i.v. The shunt fraction of portal blood F is obtained by the ratio of the areas under the plasma level vs. time curves (“AUC”) after p.o. and i.v. administrations: The pigs were divided into three experimental groups, (i) Group I: undisturbed portal flow; (ii) Group II: total diversion of portal blood with an end–to–side portacaval shunt, and (iii) Group HI: partial diversion of portal blood through a side–to–side portacaval shunt. Portal flow was measured during surgery with an electromagnetic flowmeter above and below the shunt and the degree of shunting calculated. Results show that the shunt fraction measured with ursodeoxycholic acid is well–correlated with hemodynamic data. No overlap between Groups I to III is observed. It is concluded that the shunt fraction of nutrient portal blood can be measured with this noninvasive method. Minute amounts of ursodeoxycholic acid were used in order to be completely metabolized by the liver, even in spite of hepatocellular dysfunction. Therefore, this method should be valid in cirrhotic patients and be useful to decide the type of portosystemic shunt to propose for the decompression of gastroesophageal varices.