The bladder of the mare may be turned inside out by spasmodic contraction of its walls, when it may be said to evert itself. The mucous membrane will then be on the outside. The accident is of very rare occurrence, and is usually brought about by the pains of parturition. It may, however, result from other causes where violent straining is excited, and the contents of the abdomen are forcibly pressed against the bladder at a time when possibly the opening into it is abnormally dilated.
A fleshy-looking mass, more or less rounded, projects through the vulva, varying in appearance according as the accident is recent or of some duration; at first it is a pale pinkish-red hue, darkening with exposure to a bluish or blackish red colour. The protruding organ has been mistaken for the foetal envelopes, and fatally injured by an attempt to remove them. The orifices of the ureters, by which the urine enters the bladder, may be found when carefully sought on the upper and anterior part of the protruding viscus, and these will set at rest any doubt as to the nature of the tumour. When labour pains are excited, little jets of urine are seen in some instances spurting out of them from the upper part of the extruded organ (fig. 166).
Without inversion the bladder may escape through a rupture in the vaginal wall, and continue to fill with urine, which, being unable to escape through the usual channel, rapidly adds to the bulk of the tumour and to the difficulty of its replacement. The muscular layer alone of the vaginal wall may be ruptured, and in such case the bladder will be felt through the mucous membrane.
Fig. 166. - Inversion of the Bladder.
Before making any examination of the extruded organ, our hands and implements should be rendered aseptic. Having dressed the bladder, we proceed with gentle but continuous force to push it back into the vagina, seeking there for the meatus upon the floor of the passage, and gradually directing it into place with the fingers or by means of the smooth rounded end of a short stick, which should be first freely dressed with carbolized oil.
The congestion and tumefaction which result from long exposure render the task of replacement more difficult, and the greatest caution will be required in manipulating the viscus lest the swollen and softened mucous membrane be torn. It may be needful to reduce the congestion by the application of warm flannels before reposition is attempted. The restlessness of the patient and forceful labour pains are the chief obstacles to a return of the viscus, and some restraint must be exercised to suppress them. The use of cocaine in a four per cent solution has been found helpful in producing more or less local anaesthesia, and removing the disposition to renewed expulsive efforts which the presence of the operator's hand induces.
Subsequent treatment consists in keeping the animal on soft diet and under good hygienic conditions, and the administration of anodyne medicines if pain is experienced. If a subject of this accident is again bred from, increased risk attends parturition.