**6. Diagnosis**

Diagnosis of atresia ani is based in clinical signs, physical examination findings and confirmed with radiographic examination. Evaluation of external anal sphincter muscle presence and function is important for prognostic purposes.

### **6.1 Diagnostic tests**

Penile bulb or vulva pinching may result in an anal wink (bulbourethral reflex) [Chambers, 1986; Hosgood & Hoskins, 1998]. Electro stimulation of perineal muscles using electrocautery at surgery or nerve stimulators may also be used to check for a strong anal response (Mahler & Williams, 2005). Electromyography for external anal sphincter muscle may be used if available for a more accurate evaluation of the anal tone (Ellison & Papazoglou, 2011).

#### **6.2 Radiographic examination**

Abdominal radiography is useful in atresia ani anatomic typing and ruling out colonic distention, which may lead in megacolon that affects management and prognosis (Figures 15-18). Gas accumulation in colon and rectum, as visualized in plain radiographs, may help in determining the position of the terminal rectum. Horizontal beam abdominal radiographs with the animal suspended upside down and pressure around the abdomen may help to visualize gas accumulation migrating to the terminal colon and rectum and outlining the borders of the rectal pouch (Greiner, 1972; Bright & Bauer, 1994). Additionally, a coin is placed at the anal dimple to help outline the anus (Greiner et al., 1984). In case of rectovaginal or urethrorectal fistulation positive contrast vaginography or urethrography may help determine fistula and terminal rectum location (Aronson, 2003; Prassinos et al., 2003; Viana &Tobias, 2005; Rahal et al., 2007; Ellison & Papazoglou, 2011).

Fig. 14. Rectocutaneous fistulas ventral and lateral to the tail (arrows) in a cat with type II

Diagnosis of atresia ani is based in clinical signs, physical examination findings and confirmed with radiographic examination. Evaluation of external anal sphincter muscle

Penile bulb or vulva pinching may result in an anal wink (bulbourethral reflex) [Chambers, 1986; Hosgood & Hoskins, 1998]. Electro stimulation of perineal muscles using electrocautery at surgery or nerve stimulators may also be used to check for a strong anal response (Mahler & Williams, 2005). Electromyography for external anal sphincter muscle may be used if available for a more accurate evaluation of the anal tone (Ellison &

Abdominal radiography is useful in atresia ani anatomic typing and ruling out colonic distention, which may lead in megacolon that affects management and prognosis (Figures 15-18). Gas accumulation in colon and rectum, as visualized in plain radiographs, may help in determining the position of the terminal rectum. Horizontal beam abdominal radiographs with the animal suspended upside down and pressure around the abdomen may help to visualize gas accumulation migrating to the terminal colon and rectum and outlining the borders of the rectal pouch (Greiner, 1972; Bright & Bauer, 1994). Additionally, a coin is placed at the anal dimple to help outline the anus (Greiner et al., 1984). In case of rectovaginal or urethrorectal fistulation positive contrast vaginography or urethrography may help determine fistula and terminal rectum location (Aronson, 2003; Prassinos et al.,

2003; Viana &Tobias, 2005; Rahal et al., 2007; Ellison & Papazoglou, 2011).

presence and function is important for prognostic purposes.

atresia ani

**6. Diagnosis** 

**6.1 Diagnostic tests** 

Papazoglou, 2011).

**6.2 Radiographic examination** 

Fig. 15. Abdominal radiograph of a dog visualizing gas accumulation in the colon and rectum. The location of the terminal rectum is also shown (arrow) [Courtesy Dr. M.N. Patsikas, Aristotle University of Thessaloniki].

Fig. 16. Abdominal radiograph showing megacolon associated with type II atresia ani in a dog (Courtesy Dr. M.N. Patsikas, Aristotle University of Thessaloniki).

Atresia Ani in Dogs and Cats 189

Surgical correction is considered the only treatment for atresia ani. Anatomical typing of atresia ani should be performed to help determining the type of surgical correction for each case (Ellison & Papazoglou, 2011). However, non surgical management may also be applied for type I cases (Tomsa et al., 2011; Ellison & Papazoglou, 2011). Numerous case reports have appeared in the literature reporting surgical treatment of atresia ani in dogs and cats. Currently there are only 3 small and 1 larger case series reporting surgical treatment in dogs (Prassinos et al., 2003; Vianna & Tobias, 2005; Rahal et al., 2007) and 2 small case series in cats describing surgical or medical management of atresia ani (Suess et al., 1992; Tomsa et al., 2011). Anoplasty is the most common procedure performed. The aim of surgery is to restore anorectal continuity, to preserve the external anal sphincter, to preserve or restore colonic function and to eliminate any rectovaginal or urethrorectal communication. Surgical treatment should be prompt and performed before colonic atony or megacolon associated with chronic and prolonged distention or possible urinary tract infection ensues (Prassinos et al., 2003). Animals with atresia ani type II and III that are unable to defecate if not treated surgically will die because of bowel stasis. End-on temporary colostomy may be considered as an option for the treatment of cats with rectocutaneous fistulas associated with atresia ani (Tsioli et al., 2009). The perineal approach is used for all surgical corrections of atresia types I-III. Prophylactic antibiotics (cefoxitin 20 mg/kg) are administered intravenously at

Animals with this type of atresia ani are placed in ventral decumbency and treated with resection of the strictured portion of the rectum through a 3600 anoplasty. After excision of the stricture the rectal mucosa is brought distally so as mucosa to skin apposition is achieved with simple interrupted sutures using synthetic non absorbable monofilament 4/0- 5/0 suture material (Figure 19). Care is taken during dissection to preserve the external anal

Fig. 19. Anoplasty in the dog of figure 8 with atresia ani type I.

**7. Treatment** 

anesthetic induction.

**7.1 Type I atresia ani** 

Fig. 17. Abdominal radiograph of a boxer puppy depicting colonic gas distention associated with type II atresia ani (Courtesy Dr. M.N. Patsikas, Aristotle University of Thessaloniki).

Fig. 18. Abdominal radiograph of a female rottweiler cross puppy with type III atresia ani and rectovaginal fistula showing fecal material in the colon, terminal rectum and over the vagina level. (Courtesy Dr. M.N. Patsikas, Aristotle University of Thessaloniki).
