Catheter

Catheter (Gk. katheter, a thing put in, or a thing let down), a long, hollow tube of suitable curvature employed by surgeons for introducing into or removing from internal cavities fluid or air. The term catheter is practically restricted to the urinary catheter and the Eustachian catheter. The urinary catheter is introduced through the urethra into the bladder with the object of withdrawing urine when there is some obstacle to the natural flow. The material of which such tubes are made is either metallic (silver or pewter) or composed of gum elastic or vulcanised indiarubber. Thus the catheter may be rigid or flexible; in the former case the form of the instrument is adapted to the course taken by the urethra. Thus a silver male catheter is a hollow rod of silver of about ten inches in length, and curved at the extremity which is designed to be inserted into the bladder. A female catheter is much shorter than this, corresponding to the different length of the female urethra. Flexible catheters are usually furnished with a stilet, i.e. a wire which can be passed along their length, and which can be bent so as to give them any particular shape which may be desired. Catheters are made of different sizes, varying from the No. 1 instrument, which will pass through a very constricted orifice, to the largest size, No. 12. A special form of catheter with a bolder curve is used in cases of retention of urine due to enlargement of the prostate gland, and is known as the prostatic catheter. The Eustachian catheter is introduced through the nose into the Eustachian tube, in order to admit of air being forced into that canal, in certain cases of ear disease. The instrument is a small curved catheter, some six inches in length.