Choledochosphincter inhibitory reflex: identification of the reflex in dogs and its significance

The sphincter of Oddi (SO) may undergo functional disorders. The mechanism of action of this sphincter is as yet not fully explored; the current study aims at studying some aspects of this mechanism.

Twelve mongrel dogs (mean weight 15.3 +/- 2. 9 SD kg, 8 male, 4 female) were studied. Under general anesthesia, the abdomen was opened and the gall bladder, common bile duct (CBD), and duodenum were exposed. Through separate punctures in the CBD, a balloon-tipped 2F catheter was introduced into the CBD and a 2F manometric catheter was placed within the SO. The positioning of the catheters was controlled fluoroscopically. The pressure response of the CBD and SO to CBD balloon distension with CO2, without and with separate anesthetization of either the CBD or SO, was recorded.

Upon CBD distension by 0.5 ml of CO2, the pressure in the CBD rose (P < 0.001) and in the SO dropped (P < 0.01). The SO pressure drop was momentary and did not change significantly (P > 0. 05) with increase in the volume of CBD distension. The pressure response was blocked on separate anesthetization of the CBD and SO.

The SO opening on CBD distension is suggested to be reflex and not hydromechanical. It seems to be mediated through a reflex which we call "choledochosphincter inhibitory reflex." Derangement of this reflex might result in functional disorders of the SO.