Diagnosis. The diagnosis presents no difficulty.
Prognosis. The prognosis is grave so far as the loss of milk is concerned, although the lesion has no effect on the general health. It is particularly serious, however, because it may cause the interior to become infected, and an acute parenchymatous mammitis may thus be set up. It must also be borne in mind that old fistulæ are much more difficult to obliterate than recent ones.
Treatment is much more troublesome than might at first be thought, the great obstacle to repair being the continual secretion and discharge of milk.
At first, attempts should be made to re-establish and render permanent the natural method of discharge. This can be effected by inserting an aseptic milk catheter and fixing it in position with a little pitch bandage.
The course of the fistula is then cleansed, curetted, and rendered aseptic in some way, as for example by washing with boiled salt solution and dilute hydroxyl.
As there is little hope of obliterating the fistula by merely suturing the skin, its course should first be closed by passing one or two deep sutures without touching the external orifice and without passing over it (Fig. 238). The discharge of fluid being then entirely stopped, the external portion of the fistula is thoroughly cleansed, powdered with iodoform, and finally closed with external, closely-applied sutures. These sutures are protected with a little cotton wool or collodion dressing, and healing then almost invariably occurs.
The animal should be given a very clean bed, and closely watched to prevent it tearing out the milk catheter. On the fourth or fifth day the catheter is removed, and is afterwards only used at intervals.
As all the sutures can be of aseptic catgut or silk, there is no necessity to trouble about their removal. The dressing can be left until it falls away of itself.