Since 1945, when Blakemore initiated the treatment of portal hypertension by decompressive vascular shunts between the portal and systemic venous systems, the efficacy of this form of therapy has received positive support from multiple sources.* Despite this favorable experience, there has been some reluctance in widespread acceptance of the procedure. In part, this may be due to the magnitude of the operation, the technical difficulties entailed, and the inherent risks. Of equal importance has been the inability to assess accurately the value of such shunts. At present, there is no exact method of determining postoperatively whether the shunt is patent or thrombosed, so that clinical evaluation of operative series must be made without this essential information.
The importance of a simple method to establish definitely the status of the anastomosis has been recognized for some time and has been the subject of considerable investigation. Heretofore, the problem has been approached