In performing the operation of crushing, the horse is thrown as for castration, and when under the influence of chloroform the urethra is opened in precisely the same manner and place as directed for lithotomy. The neck of the bladder is then dilated, and the lithotrite (fig. 158), nicely warmed and smeared with oil, is passed into it. The blades of the instrument are then drawn as far apart as may be necessary to receive the stone. The next step is to bring the calculus fairly between them. To accomplish this the lithotrite should be held by one hand applied near the blades, the screw being in charge of an assistant who will also steady the instrument while the seizure is being effected. With the other hand in the rectum the operator now proceeds to manipulate the stone, and by a little careful manoeuvring directs it into the jaws of the lithotrite. The assistant, on being instructed, will then turn the screw until the calculus is secured.
Having obtained a good hold of the stone a half-turn is given to the lithotrite, first towards the right, then the left, so as to determine if any portion of the mucous membrane has been included in the grasp of the instrument. To obviate this it is usual in man to operate with the bladder distended with urine, but in the horse the fluid qickly drains away through the perineal wound, and cannot therefore be made available for keeping the walls of the organ away from the calculus.
When the stone has been satisfactorily secured, the screw is brought again into action, and the operation of crushing proceeded with. This done, the broken fragments are freed from the lithotrite and removed with the forceps (fig. 159) and scoop (fig. 160), aided by repeated injections of warm carbolized water as directed for lithotomy.
Should the operation prove troublesome and protracted, it may be necessary to defer completing the operation to a future day, in which case a light diet should be prescribed for a few days, say from three to seven, when the operation may be again renewed, and, if possible, carried to completion. In the meantime portions of stone may enter the perineal orifice and become arrested in it. These are to be carefully removed, and it may be necessary also to pass the catheter to discharge any debris which may have accumulated in the urethral canal. In addition to this the bladder will require to be thoroughly washed out once daily with warm carbolized water for the first two or three days, after which it may be discontinued.
Fig. 158. - Lithotrite.
Fig. 159. - Forceps for Lithotripsy.
Fig. 160. - Scoop.
On completion of the operation the bladder should be carefully searched with the short metallic sound (fig. 161), and if found free from fragments of stone it only remains to remove the animal to his box. He should then be dealt with according to the rules laid down for the after-treatment of lithotomy. An opiate draught, followed by warm fomentations to the perineum with carbolized water and periodical injections of warm water into the rectum, will serve to soothe the injured parts and allay irritation.
Fig. 161. - Sound.