Preparing the patient for the operation of lithotomy or lithotrity is in all cases more or less desirable. It should ever be borne in mind that the aim and object of extracting a stone is not merely the accomplishment of a surgical feat, but to preserve life, and, what is equally important from an economic point of view, the utility of the patient. Every means, therefore, tending to ensure success should be fully considered and adopted.
In entering upon the operation the bladder should be fairly distended with urine, when the horse should be cast, as for the operation of castration. The penis and sheath are now thoroughly cleansed, and all fsecal matter removed from the rectum. The administration of chloroform is now proceeded with, and when the animal is fully under its influence the hind-cmarters are raised by under-packing with straw, and the patient, having been placed on his back, is supported on either side and held steadily in position. The penis is now unsheathed, thoroughly washed and disinfected, and a well-oiled grooved staff (fig. 150) is introduced into the urethra, and pressed carefully onwards towards the bladder by an assistant, the operator guiding the course of the instrument along the perineum with the left hand, while the right, which is in the rectum, directs the point towards the bladder. By a little manoeuvring the groove of the staff is brought to face the perineum, and the assistant is instructed to press the instrument toward the abdomen, and hold it steadily in position. A scalpel is then taken in the right hand, and the skin of the perineum being stretched by the left forefinger and thumb, is incised along the central line from the pubic arch to within an inch or less of the anus. The point of the knife (fig. 151) is now forced through the walls of the urethra into the groove of the staff, and an opening made according to the size of the orifice required for the passage of the stone. A bullet-headed whalebone probe (fig. 153) is now introduced into the groove, along which it is directed into the bladder.
Fig. 150. - Grooved Staff.
The staff is then withdrawn, and the disinfected finger, following the course of the probe, is next passed into the cavity, the probe at the same time being withdrawn.
The deeper wound, i.e. the urethral orifice, must now be enlarged by extending the incision along the same line through the membranous urethra. This will be effected with the least risk with the probe-pointed bistoury (fig. 152), the finger in the passage acting as guide and lever in performing the section. In carrying out this part of the operation the knife should be well under control. This incision is made from within outwards, deliberately but with caution, always remembering that the rectum lies immediately beneath, and stands in danger of being cut. Such a result, it need hardly be pointed out, would not only seriously complicate the case, but place the animal's life in jeopardy.
Fig. 151. - Lithotomy Knife (sharp-pointed).
Fig. 152. - Lithotomy Knife (blunt-pointed).
Fig. 153. - Whalebone Probe.