An Improved Cannula for Gastric and Intestinal Fistulas

The care of dogs with cannulated gastric or intestinal fistulas is often difficult because many of the animals will pull their cannulas out at the first opportunity. In the latter part of the year 1938 we undertook to design a cannula which could not be pulled out. To accomplish this it was necessary to use a larger inner flange than could conveniently be installed when the cannula was constructed in the usual way. The cannula was. therefore, designed with a removable flange which could be inserted separately into the stomach or intestine; the remainder of the cannula could then be attached to it. Once the flange is inserted, no great force can be applied to it through the visceral wall because of danger of injuring the mucosa; consequently, it was necessary to provide a wrench which could be applied through the lumen for tightening the flange on the cannula. The cannula and the wrench are illustrated in Fig. 1.

To install the cannula, the viscus to be cannulated (stomach or intestine) is secured through an abdominal incision and an opening made, barely large enough to admit the separated flange. After the flange has been inserted, the appropriate end of the inner tubular portion of the cannula is inserted through the opening and screwed into the flange, as far as possible, by hand. The wrench is then assembled inside the cannula in such a way that the hooks on the lower ends of the 1/8 inch rods grasp the flange in its narrow diameter. The tapered plug with a knurled head is slid down the 3/8 inch rod and rotated until the fins which project from its sides fall into the grooves on the inner aspect of the cannula; the screw joint is then firmly tightened.