612 ANAL FISTULA AND RECTO- VAGINAL FISTULA. 



the rectal opening 6 inches in advance of the anus, the second on the lower 

 surface of the tail. " Incomplete " anal fistulae in horses have been seen 

 by Hertwig ; one was 12 inches, the other 16 inches in length, and both 

 had resulted from abscess formation. Novotny describes a fistula com- 

 municating with the rectum, and extending between the semi-tendinosus 

 and biceps femoris muscles. 



Diagnosis may be confirmed by probing the channel while a 

 finger is inserted in the rectum ; if the fistula is complete, the finger 

 will encounter the end of the probe, and the position of the opening 

 of the fistula will be discovered. Sometimes, owing to the sinuous 

 course of the channel or the existence of branches, exploration by 

 probing is unsatisfactory, and more information can be obtained 

 by injecting the fistula with coloured fluid. 



Treatment. To prevent anal fistula, proper treatment of 

 wounds, &c, is very important, and injuries of the vaginal walls 

 during delivery must receive special attention. 



It is possible to bring about closure by injecting irritants like 

 liquor Villati, iodine, sublimate and zinc chloride ; but when fistulse 

 extend into the rectum, or far forwards in the paraproctal connective 

 tissue, the use of irritants is dangerous, on account of the possibility 

 of their reaching the peritoneal cavity. Operation with free exposure 

 of the fistula is therefore preferable. If possible, the sphincter ani 

 must be spared, though its section often produces no lasting incon- 

 venience, and union becomes quite perfect. Munkel divided the 

 sphincter without bad results ; Hertwig endeavoured to spare it 

 as far as possible. In laying open a " complete " anal fistula a grooved 

 director is inserted, the end of the fistula discovered by inserting the 

 index finger of the left hand in the rectum, and an incision then made 

 down to the finger, care being taken to spare the soft parts as much 

 as possible, and so regulate the cut as to favour wound drainage. 

 Roupp passed a lead wire through a " complete " rectal fistula, drew 

 one end back through the anus, and laid open the fistula by daily 

 tightening the wire about an inch. Novotny secured healing in 

 one case by drainage. Cauterization of the fistulous track by means 

 of a thick wire or steel probe, heated to a bright red, may succeed 

 when other treatment fails. Roder sutured a recto-vaginal fistula 

 but only obtained partial union. Short recto-vaginal fistula may 

 sometimes be closed by passing a seton ; the larger lying near the 

 vulva may be sutured. 



VIII.— TUMOURS IN THE RECTUM AND ANUS. 

 In dogs fibromata, sarcomata, carcinomata, and adenomata 

 are not infrequently seen in the paraproctal connective tissue ; while 



