Nonpassage of contrast media into the duodenum may be caused by spasm of the sphincter of Boyden and is a well-recognized diagnostic problem in operative cholangiography. Chessick et al (see pp 53-57) have alerted the surgeon to the possible etiologic role of fentanyl. If fentanyl is found to directly induce or potentiate spasm in a majority of patients, an alternative anesthetic may be advised during biliary surgery.
As Chessick et al also point out, however, there are many variables in operative cholangiography and a number of these might induce spasm. In 56 postcholedochotomy cholangiograms reported by Ginzburg et al,1 no duodenal drainage was seen in 24 (43%), but subsequent postoperative T-tube cholangiography was normal for all of these patients. No mention was made of the anesthetic used. Baker2 has noted a 25% incidence of pseudo-obstruction after common duct instrumentation. Such high incidences of apparent obstruction due to spasm