Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

Treatment: Surgery is the most effective treatment and may include tail
amputation. Cyclosporine and other immune-mediating medications may
also be helpful in treating perianal fistulas. Perianal fistulas are difficult to
cure and are associated with postoperative complications and recurrences.
Early treatment offers the best chance for recovery. Cryotherapy and laser
treatments have been used with success. Unfortunately, many surgical treatments
may leave the dog with a degree of fecal incontinence.
RECTAL POLYPS AND CANCERS
Polyps are benign, grapelike growths that occur in the rectum and may protrude
from the anus. They are not common, but when present they should be
removed.
Adenocarcinoma is the most common malignant colorectal growth, followed
by lymphoma. Adenocarcinomas are slow-growing gastrointestinal
tumors found predominantly in older dogs, usually in the lower colon and rectum.
These tumors can obstruct, ulcerate, and bleed. The diagnosis is made by
colonoscopy and biopsy of the tumor.
Cancers can also arise from the anal sacs. This occurs primarily in older
females. Anal sac adenocarcinomas have the unique property of producing
parathyroid hormone, and thus may be associated with a severe form of hypercalcemia
(see Hyperparathyroidism, page 407). These tumors vary in size from
small lumps that are barely palpable to large masses protruding from the rectum.
Treatment: Surgical resection is the treatment of choice for colon and rectal
cancers. Lymphomas can be treated with chemotherapy. Anal sac adenocarcinomas
are best treated by surgical excision. Chemotherapy is a
consideration for large tumors. Radiation may also be part of the treatment
regimen.
PERIANAL GLAND TUMORS
THE DIGESTIVE SYSTEM • 293
These common tumors, often multiple, arise from glands located around the
anus and at the base of the tail. They occur primarily in intact males over 7
years of age, and require the presence of testosterone. Adenomas can be recognized
by their typical location and rounded, rubbery appearance. A minority
undergo malignant transformation to adenocarcinomas. These cancerous
neoplasms can grow to a large size, break through the skin, become infected,
and cause anorectal obstruction. Metastases to the lungs occur frequently.
Treatment: The diagnosis is confirmed by tissue biopsy. For small tumors,
this is best done by completely excising the tumor. If the tumor is found to be
malignant, a chest X-ray should be taken to rule out metastatic spread.
Perianal gland tumors may regress completely following removal of the testicles.
Thus, all dogs with perianal tumors, whether benign or malignant,