**7.2 Type II & III atresia ani**

For animals with type II or III atresia ventral recumbency is used and a cruciate, vertical or vertical elliptical incision is made over the anal dimple and medial to the ducts of the anal sacs. The triangular flaps or elliptical skin created are excised. The external sphincter and distal rectal pouch are identified and dissection is continued medial to the sphincter using fine scissors. The rectum is mobilized through the sphincter by using stay sutures, opened and sutured to the subcutaneous tissue and skin with 4/0-5/0 monofilament absorbable or non absorbable suture material respectively (Figures 20-22). In some animals with Type III atresia ani the rectal pouch is located more than 1 cm away from the anal dimple dissection for identification and mobilization of the rectum is achieved through rectal pull through procedure. The colon and rectum should be evacuated from feces before recovery, while the animal is still in anesthesia, to promote normal intestinal function (Hosgood & Hoskins, 1998; Aronson, 2003; Prassinos et al., 2006; Ellison & Papazoglou, 2011).

Fig. 20. The rectal pouch was identified through a cruciate incision made over the anal dimple in a puppy of figure 9. Two stay sutures were placed in the rectum to allow easy handling.

sphincter and anal sacs (Hosgood & Hoskins, 1998; Aronson, 2003; Prassinos et al., 2003; Ellison & Papazoglou, 2011). Type I atresia ani may also be treated with bougienage or balloon dilatation in a single or multiple treatments; however, failures are not uncommon (Hosgood & Hoskins, 1998; Webb et al., 2007; Tomsa et al., 2011; Ellison & Papazoglou, 2011). Recently, a single balloon dilatation procedure alone or combined with intralesional triamcinolone injection was used to successfully treat type I atresia ani in 5 kittens and two dogs (Webb et al., 2007; Tomsa et al., 2011). Prospective studies are needed to evaluate balloon dilatation for the treatment of congenital anorectal strictures in small

For animals with type II or III atresia ventral recumbency is used and a cruciate, vertical or vertical elliptical incision is made over the anal dimple and medial to the ducts of the anal sacs. The triangular flaps or elliptical skin created are excised. The external sphincter and distal rectal pouch are identified and dissection is continued medial to the sphincter using fine scissors. The rectum is mobilized through the sphincter by using stay sutures, opened and sutured to the subcutaneous tissue and skin with 4/0-5/0 monofilament absorbable or non absorbable suture material respectively (Figures 20-22). In some animals with Type III atresia ani the rectal pouch is located more than 1 cm away from the anal dimple dissection for identification and mobilization of the rectum is achieved through rectal pull through procedure. The colon and rectum should be evacuated from feces before recovery, while the animal is still in anesthesia, to promote normal intestinal function (Hosgood & Hoskins, 1998; Aronson, 2003; Prassinos et al., 2006; Ellison &

Fig. 20. The rectal pouch was identified through a cruciate incision made over the anal dimple in a puppy of figure 9. Two stay sutures were placed in the rectum to allow easy

animals.

**7.2 Type II & III atresia ani** 

Papazoglou, 2011).

handling.

Fig. 21. The rectum of the dog of figure 9 was mobilized and opened to allow an anoplasty procedure.

Fig. 22. The rectal mucosa of the dog of figure 9 was sutured to the skin with simple interrupted nylon sutures to complete the anoplasty.

#### **7.3 Type IV atresia ani**

Animals with this type of atresia may need an abdominal approach to isolate, mobilize and anastomose the cranial colon with the distal colon and rectum usually through a pubic symphisiotomy procedure (Hosgood & Hoskins, 1998; Aronson, 2003).

Atresia Ani in Dogs and Cats 193

Fig. 24. Atresia ani type III associated with a rectovaginal fistula. The fistulous tract grasped

Fig. 25. Atresia ani type III associated with a rectovaginal fistula. The fistulous tract was sutured to the external anal sphincter and the vaginal mucosa was closed with simple

**7.5 Temporary end-on colostomy for the management of cats with rectocutaneous** 

Temporary incontinent end-on colostomy may be performed initially for fecal diversion to help eliminate rectocutaneous fistulas. Colostomy is located in the lateroventral abdominal

with mosquito hemostats was dissected from the vagina.

interrupted sutures.

**fistulas associated with type II atresia ani** 

#### **7.4 Types II-III atresia ani with rectovaginal fistula**

Three surgical techniques are used for the correction of rectovaginal fistula in dogs and cats. Initial approach is through a vertical midline perineal incision extending from the ventral anus to the vulva. In one technique the fistula is isolated, excised and the rectal and vulvar lumens are ligated or oversewn separately with 3/0 -4/0 monofilament absorbable suture material or hemostatic clips followed by closure of the vertical perineal incision; An anoplasty procedure for atresia correction as previously described is performed afterwards (Chambers, 1986; Hosgood & Hoskins, 1998; Aronson, 2003; Prassinos et al., 2003; Viana &Tobias, 2005; Rahal et al., 2007; Ellison & Papazoglou, 2011). Fistula obliteration by performing numerous purse-string sutures placed along its length was also described in a dog (Louw & van Schouwenburg, 1982). According to another technique, used in 3 cats and 1 dog, the rectum is transected cranial to the fistulous opening, the affected rectal portion is excised and the terminal part of the rectum is sutured to the anus (Rawlings & Capps, 1971; Suess et al., 1992; Aronson, 2003). In the third technique the fistulous tract is preserved, isolated, mobilized through the anus and sutured to the skin at the level of the external anal sphincter; this technique was used for anal reconstruction in 2 dogs (Prassinos et al., 2003; Ellison & Papazoglou, 2011) and 1 cat (Bornet, 1990) and modified to be performed in 2 dogs through an episiotomy approach (Mahler &Williams, 2005) [Figures 23-25]. With this technique the preserved fistulus tract is considered the terminal part of the rectum and thus function of the internal anal sphincter is maintained (Prassinos et al., 2003; Mahler & Williams, 2005).

Fig. 23. Atresia ani type III associated with a rectovaginal fistula. The fistulous tract of the dog of figure 12 was isolated through a vertical midline perineal incision extending from the anus to the vulva. A pair of closed needle holders was inserted through the tract.

Three surgical techniques are used for the correction of rectovaginal fistula in dogs and cats. Initial approach is through a vertical midline perineal incision extending from the ventral anus to the vulva. In one technique the fistula is isolated, excised and the rectal and vulvar lumens are ligated or oversewn separately with 3/0 -4/0 monofilament absorbable suture material or hemostatic clips followed by closure of the vertical perineal incision; An anoplasty procedure for atresia correction as previously described is performed afterwards (Chambers, 1986; Hosgood & Hoskins, 1998; Aronson, 2003; Prassinos et al., 2003; Viana &Tobias, 2005; Rahal et al., 2007; Ellison & Papazoglou, 2011). Fistula obliteration by performing numerous purse-string sutures placed along its length was also described in a dog (Louw & van Schouwenburg, 1982). According to another technique, used in 3 cats and 1 dog, the rectum is transected cranial to the fistulous opening, the affected rectal portion is excised and the terminal part of the rectum is sutured to the anus (Rawlings & Capps, 1971; Suess et al., 1992; Aronson, 2003). In the third technique the fistulous tract is preserved, isolated, mobilized through the anus and sutured to the skin at the level of the external anal sphincter; this technique was used for anal reconstruction in 2 dogs (Prassinos et al., 2003; Ellison & Papazoglou, 2011) and 1 cat (Bornet, 1990) and modified to be performed in 2 dogs through an episiotomy approach (Mahler &Williams, 2005) [Figures 23-25]. With this technique the preserved fistulus tract is considered the terminal part of the rectum and thus function of the internal anal sphincter is maintained (Prassinos et al., 2003; Mahler &

Fig. 23. Atresia ani type III associated with a rectovaginal fistula. The fistulous tract of the dog of figure 12 was isolated through a vertical midline perineal incision extending from the

anus to the vulva. A pair of closed needle holders was inserted through the tract.

**7.4 Types II-III atresia ani with rectovaginal fistula** 

Williams, 2005).

Fig. 24. Atresia ani type III associated with a rectovaginal fistula. The fistulous tract grasped with mosquito hemostats was dissected from the vagina.

Fig. 25. Atresia ani type III associated with a rectovaginal fistula. The fistulous tract was sutured to the external anal sphincter and the vaginal mucosa was closed with simple interrupted sutures.

#### **7.5 Temporary end-on colostomy for the management of cats with rectocutaneous fistulas associated with type II atresia ani**

Temporary incontinent end-on colostomy may be performed initially for fecal diversion to help eliminate rectocutaneous fistulas. Colostomy is located in the lateroventral abdominal

Atresia Ani in Dogs and Cats 195

Table 2. Algorithm for atresia ani treatment methods in dogs and cats. RVF : rectovaginal

Postoperative complications may include tenesmus, fecal incontinence, wound dehiscence, stricture of the anoplasty, colonic atony or megacolon and rectal prolapse (Suess et al., 1992; Prassinos et al., 2003; Vian & Tobias, 2005; Rahal et al., 2007; Ellison & Papazoglou, 2011). Fecal incontinence, a common complication after surgery, may be transient (Prassinos et al., 2003; Viana & Tobias, 2005, Rahal et al., 2007), intermittent or permanent (Suess et al., 1992; Ellison & Papazoglou, 2011) and related to a congenital absence of functional external anal sphincter or surgical trauma to the sphincter muscle innervation during dissection (Aronson, 2003; Prassinos et al., 2003; Viana & Tobias, 2005; Ellison & Papazoglou, 2011). Fecal incontinence secondary to surgical intervention in dogs may resolve several weeks to a year after surgery (Prassinos et al., 2003; Viana & Tobias, 2005; Rahal et al., 2007). Semitendinosus muscle flap application was proposed as an option to improve anal tone in a dog with atresia ani and rectovaginal fistula (Chambers & Rawlings, 1991). Wound dehiscence may be related to tension on the anastomosis and fecal contamination of the surgical site (Suess et al., 1992) and may be prevented by meticulous surgical technique. Stricure of the anoplasty site and fecal retention associated with colonic atony or megacolon are two common complications requiring a second surgery such as revision anoplasty, subtotal colectomy or colotomy (Viana & Tobias, 2005, Ellison & Papazoglou, 2011). Animals with stricture of the anoplasty site may develop tenesmus, constipation and fecal impaction. This complication may need a revision anoplasty or baloon dilatation to resolve. In a recent study with 12 cases of dogs and cats with atresia ani having surgical management, 5 animals with type II-III atresia ani, 4 of which combined with rectovaginal fistula, developed postoperative stricture and had initially balloon dilatation, which failed in all but one case.

fistula

**9. Complications** 

wall. Soon after colostomy and following resolution of fistulas a second surgery is performed for colostomy closure and reconstruction of the atresia ani by performing anoplasty (Tsioli et al., 2009) [Figures 26 & 27].

Fig. 26. Following resolution of fistulas the colostomy was closed (arrow) and an end to end colocolonic anastomosis was performed (arrowhead) through a ventral midline celiotomy in a cat.

Fig. 27. Atresia ani reconstruction through anoplasty was performed following colostomy closure in a cat.
