Several instruments are made for this purpose, the principle of all, however, is the same, namely, a tube within a tube, the inner carrying the supply of fluid, and the outer serving for a drain. An extemporized instrument may be made out of a large and a small catheter, passing the latter through the former and using the smaller for the ingress, the other for the egress.
Also, quite as satisfactory results are obtained by the use of a single tube, in which case a quantity of fluid is allowed to flow into the bowel. The tube is then disconnected from the supply and the contents of the bowel pass out through the tube. The tube may now be connected again and the process repeated till the fluid comes away clear. A tube suitable for this purpose is the one used for enemata, a soft, but rather rigid, tube about eighteen inches long, known as the "rectal tube." They are made with closed end and side fenestra, as well as with an open end.
The other necessary appurtenances are the fluid to be used for irrigation and a reservoir for containing it, which should be elevated about three or four feet. For the latter may be used any vessel, its contents being syphoned out, but very much preferable is a glass reservoir with an opening at the bottom. This makes it possible not only to see how much fluid is available at any time but also to form an idea of how fast it is discharging. The bottles for this purpose are easily cleaned and possess the further advantage of remaining practically sterile while in use. The size varies, but the larger have the advantage of maintaining the temperature of their contents more uniformly, and are much more serviceable.
In colon irrigation the patient may be in the dorsal position, with the hips elevated, in which case a douche pan will be a great convenience, or a Kelly pad, or a folded rubber sheet may be used.
As the chief object of this procedure is the cleansing of the bowel, a considerable amount of fluid is necessary, but its composition is of secondary importance. The physiologic saline solution is generally used (approximately a heaping teaspoonful of salt to a quart of water), at a temperature of about 100° F. If desired, borax, boric acid, hydrogen peroxide, potassium permanganate, silver nitrate, or other solutions may be used.