Tumors of the rectum are likely to have a multitude of inciting causes. Rectal tumors are best treated by complete surgical
excision. Good to excellent results are generally obtained with resections of rectal polyps or carcinoma in situ. Recurrences occur in only a few cases. Radical full-thickness resection of adenocarcinomas has been recommended, but dogs
undergoing cryosurgery and local excision may have a better outcome. Wound dehiscence, infection, rectal stricture and fecal
incontinence are significant complications associated with radical excision. The prognoses for rectal polyps, carcinoma in situ, leiomyomas and fibromas are generally favorable. Adenocarcinomas, lymphosarcomas and plasmacytomas tend to recur. Dogs with
annular colorectal adenocarcinomas have a particularly poor prognosis with average survival time of only 1.6 months.
Perianal fistula, or anal furunculosis, is a chronic debilitating condition of dogs characterized by single or multiple ulcerated
sinuses that can involve up to 360 degrees of the perianal tissue. True fistulous tracts from the anorectal canal to the perianal
skin are uncommon in the dog, yet the term perianal fistula has persisted. Dogs with perianal fistula are typically presented
with tenesmus, dyschezia, fecal incontinence, licking of the anal area, anal bleeding, constipation and/or a malodorous anorectal
discharge. Anorexia and weight loss also can occur in some dogs with severe ulceration or infection. Large-breed dogs are
most commonly affected, with the highest incidence in German Shepherds and Irish Setters. Physical examination of the anorectum
may require sedation or anesthesia in some dogs because of extreme pain. Examination usually reveals single or multiple areas
of ulceration, fistulous tracts and a purulent exudate with frank hemorrhage. Anorectal palpation may reveal multiple rectocutaneous
fistulas and anal stenosis.
Ruptured anal sac abscess and perianal adenocarcinoma are the only important differential diagnoses. Anal sac rupture is usually
seen as a unilaterally draining tract located ventrolateral to the anus. The cellulitis and fistulation associated with anal-sac
rupture is usually less extensive than with perianal fistula. The anal sacs may also be involved in animals affected with
perianal fistula, rendering definitive diagnosis difficult. Perianal adenocarcinoma usually has a proliferative raised appearance,
although ulceration is common, and they may grossly resemble perianal fistula.
Severe cases generally require both medical and surgical management. The principles of medical management include removal
of perineal hair, cleansing and debridement; antibacterial therapy; immunosuppressive therapy; and dietary therapy. Novel
antigen diets may affect clinical improvements in some cases, but complete resolution generally requires the concurrent use
of immunotherapy. Immunosuppression with azathioprine, cyclosporine or tropical tacrolimus has proved useful in inducing remission
in severely affected cases. Thereafter, periodic use of the immunosuppressive drugs may be required for control.
What's your question?
Send your pediatric/geriatric related questions to: Pediatric/Geriatric Protocol,
, 7500 Old Oak Blvd., Cleveland, OH 44130. Your questions will be answered by Dr. Hoskins in upcoming columns.
Dr. Hoskins is owner of DocuTech Services. He is a diplomate of the American College of Veterinary Internal Medicine with
specialities in small animal pediatrics. He can be reached at (225) 955-3252, fax: (214) 242-2200, or e-mail: