Chapter 75 Anorectal Surgery
Surgery of the rectum and anus is associated with a high rate of complications. The high bacterial population of the rectum increases the risk of wound infection and dehiscence. Bowel preparation with multiple enemas can mechanically remove large numbers of bacteria; however, enemas should not be done within 8 hours of anorectal surgery to avoid leakage of rectal contents during surgery. Prophylactic antibiotics are indicated with surgery of this area due to high numbers of bacteria. Synthetic absorbable sutures or monofilament non-absorbable sutures are recommended for surgery of the rectum and anus.
ANATOMY
The rectum begins at the brim of the pelvis and joins the anal canal just inside the anal opening. The anal canal is approximately 1 to 2 cm in length. The circumanal glands, anal glands, and anal sacs are associated with the anus.
The rectum receives its blood supply from the caudal mesenteric artery and its branch coursing caudally, the cranial rectal artery. This artery forms anastomoses with the middle and caudal rectal arteries, which arise, in the male, from the prostatic artery, and in the female, from the internal pudendal arteries. At the caudal demarcation of the rectum are two anal sphincters (internal and external). Fecal continence is maintained by these sphincters, and surgery in this area always threatens their integrity.
RECTAL PROLAPSE
Rectal prolapse is almost exclusively limited to young dogs and cats. The most common cause is straining to defecate, associated with severe colitis or proctitis due to endoparasites. Other causes include foreign bodies, rectal neoplasia, dystocia, and, in the cat, persistent straining related to urethral obstruction or cystic calculi.
Differentiate this condition from prolapsed intussusception. In the latter condition, a probe can be inserted and advanced cranially into a space between the cylindrical mass and the edge of the anus. This cannot be done with rectal prolapse.
Preoperative Considerations
Surgical Procedure: Resection and Anastomosis
Technique
Postoperative Care and Complications
Short Term
ANORECTAL STRICTURE
Causes of anorectal stricture can be benign (e.g., inflammation) or malignant (e.g., adenocarcinoma):
Preoperative Considerations
Simple, annular non-neoplastic lesions that are not too cranial in location may respond to a series of bougienage or balloon dilations. During this therapy, give prednisolone for 10 to 14 days (1 mg/kg q12h).
Surgical Procedure: Resection/Anastomosis with Rectal Pull-Through
Technique
ANAL STRICTURE LIMITED
Causes, preoperative considerations, and objectives are similar to those for anorectal strictures, as described in the previous section.
Surgical Procedure
ATRESIA ANI
This condition exists in several forms, the most common being type I (imperforate anus) and type II, in which the rectal pouch is located cranial to the membrane overlying the anus. Regardless of the type, the main problem is loss of continuity between the rectum and anus during embryonal development of the cloacal membrane.

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