The influence of measuring catheter diameter on direct manometry in the canine sphincter of Oddi.

Sphincter of Oddi manometry was performed in three anesthetized dogs, using different measuring catheter diameters, ranging from 1.0 to 1.9 mm. No differences were seen either in sphincter of Oddi wave amplitude, frequency, and base-line pressure or in common bile duct pressure measured after cannulation during 20 min with catheters of 1.0 and 1.3 mm. However, significant disturbances of these variables were present when the measuring catheter diameter was 1.6 and 1.9 mm. It is concluded that the diameter of the recording catheter is of crucial importance in sphincter of Oddi manometry. In dogs with a body weight of 30-40 kg, the outer diameter should not exceed 1.3 mm.