"Anal Sac Disorders" TUMOR TIDBITS, A BIWEEKLY VETERINARY ONCOLOGY E-LETTER Volume 3; Number 25; July 12, 2002. Editor: Kevin A. Hahn, DVM, PhD, Dipl - ACVIM (Oncology) & Overall Nice Guy! ANNOUNCEMENTS * It was great to visit with some fellow Texans Thursday in Nashville at the AVMA Convention. Next stop, the Veterinary Cancer Society Meeting in Manhattan September 12-14! * Sugar Land is OPEN for consultations with Dr. Janet Carreras. Our thanks to the veterinary communities of Sugar Land, Missouri City, Stafford, Katy and others for making this a successful venture for Gulf Coast Veterinary Oncology. * We're still enrolling dogs with lymphoma into a clinical trial using a novel antiangiogenic agent. It is for dogs with relapsed lymphoma and the criteria for entry are strict. Call or email us for additional details. THIS WEEK'S TUMOR TIDBIT: ANAL SAC DISORDERS ============================================ HERE'S WHAT'S IN THE TEXTBOOKS: OVERVIEW * Anal sac disorders of dogs can be divided into three types: impaction, sacculitis, and abscesses. All probably represent various stages of the same disease process. * Anal sac disorders are rare in cats. Impaction is noted on occasion. * Anal sac carcinoma is a malignant neoplasm derived from apocrine glands of the anal sac. * Perianal gland tumors arise from modified sebaceous glands of the skin. They are often benign (adenoma) but may be malignant (adenocarcinoma). * Anal sac carcinoma may be hormonally influenced since it occurs primarily in females. * Anal sac carcinomas invade surrounding tissues and metastasize to the regional lymph nodes. * Pperianal tumors (i.e., adenoma) affect the skin at the site of origin, around the anus; adenocarcinoma invades locally and causes distant metastasis. * Hypercalcemia (paraneoplastic syndrome) adversely affects renal function in some patients. * Perianal gland tumors may be caused by androgen stimulation since they occur predominantly in males. Combined androgenic and estrogenic influences may be involved because when they do occur in females, spayed females are more commonly affected than sexually intact females. SIGNS & PHYSICAL FINDINGS * Anal/Perianal Sac Disease--scooting, tenesmus, perianal pruritus, tail chasing, perianal discharge if abscess ruptures, behavioral changes, pyotraumatic dermatitis. * Perianal tumors--presence of a mass (often multiple), licking at the anal region, and scooting. * Perianal tumor--adenomas are usually nonfixed, encapsulated masses in the skin around the anus. May be present along dorsal midline beginning at the neck, tail, and ventral midline, especially on the prepuce, ending at the umbilicus. They may become ulcerated secondary to self-trauma. Adenocarcinomas are fixed to the underlying tissues and will metastasize, often to sublumbar lymph nodes and distant organs. * Anal sac carcinoma--presence of a mass, difficult defecation, anorexia, polyuria and polydipsia. * Anal sac carcinoma--mass originating in the anal sac. Sublumbar lymphadenopathy (metastasis) is common. CAUSES AND RISK FACTORS * Anal sacculitis--unknown, but possible predisposing factors include chronically soft feces, recent diarrhea, excessive glandular secretions, and poor muscle tone; retained secretions may lead to infection and abscessation; small breed dogs, including miniature poodles, toy poodles, and chihuahuas are reportedly predisposed to anal sac carcinoma. * Perianal tumors--intact males; dachshund, cocker spaniel, German shepherd dog, beagle, English bulldog, and samoyed. * Anal sac carcinoma--females (either intact or spayed) DIFFERENTIAL DIAGNOSES * Perianal pruritus may be caused by food hypersensitivity, flea allergy dermatitis, atopy, tapeworms, tail fold pyoderma, and seborrheic skin disorders affecting the perineum. * Anal sac abscesses need to be differentiated from perianal fistulas. * Anal sac neoplasia may also cause erythema and swelling of the perineum. * Tumors of other glands in the perineum including dermal sebaceous and apocrine glands as well as merocrine anal glands. * Other cutaneous tumors--cutaneous malignant lymphoma, squamous cell carcinoma, mast cell tumor. DIAGNOSTIC APPROACH * The history and examination of the anal sacs by digital palpation will establish the diagnosis. If easily palpated through the skin, they are considered enlarged. * On expression, normal anal sacs fluid is clear or pale yellow-brown. Thick, pasty brown secretion is characteristic of impaction, and creamy yellow or thin green-yellow secretion is often seen in animals with anal sacculitis. * Abscessed anal sacs are often associated with a red-brown exudate, fever, swelling, and erythema over the anal sacs. Ruptured anal sacs will have a discharging sinus. * Cytology of anal sac contents can help establish whether infection is present based on the number of leukocytes and bacteria. * Bacterial culture and sensitivity may be helpful in animals with chronic or recurrent anal sac infections. * Cytologic examination of fine-needle aspirate to rule out conditions other than anal sac or perianal tumors; however, differentiation of benign versus malignant is seldom possible. * Anal sac carcinoma--high serum calcium and occasionally concurrent hypophosphatemia; secondary renal failure may occur with hypercalcemia. * Perianal tumors--laboratory results usually normal. * Abdominal radiography to evaluate sublumbar lymph nodes. * Thoracic radiography should be done, but pulmonary metastasis is not common. * Surgical biopsy required for a definitive diagnosis; whenever possible, excisional biopsy should be done. OVERALL TREATMENT CONSIDERATIONS * Expressing the contents is indicated to treat anal sac impaction or sacculitis. * Instilling an antibiotic/corticosteroid ointment into infected anal sacs is helpful. * If not already present, drainage should be established in abscessed anal sacs. These should be cleaned and flushed. * If anal sacs abscess recurrently, anal sac excision should be considered. * Systemic and topical antibiotics are indicated to treat anal sac abscesses. * Hospitalization and diuresis required if hypercalcemia and resultant renal failure dictates; saline diuresis (200 ml/kg/day if possible) and furosemide (1-2 mg/kg PO q6h-q12h) should be given to reduce serum calcium. * Perianal adenomas--if orchiectomy is rejected in males, consider treatment with estrogen. SURGICAL CONSIDERATIONS * Excisional biopsy may be required depending on the severity of the presentation. * Anal sac/Perianal gland tumor--if metastasis has occurred to the sublumbar lymph nodes, consider abdominal surgery and resection of affected nodes. * In males with multiple or large perianal adenomas, castration and observation for 4-6 weeks is recommended before attempting aggressive surgery. Orchiectomy alone often causes the tumors to go into complete remission. * Cryosurgery offers no advantage over conventional surgery. * Fecal incontinence may develop if more than 50% of the anal sphincter is resected or destroyed by freezing. If fewer than 50% is resected or frozen, transient (approximately 1 week) of fecal incontinence is likely. PROGNOSIS Anal sac abcesses * Anal sac abscesses should be examined after three to seven days of therapy. If conventional medical therapy fails, excision is required. Perianal tumors * Prognosis good in patient with adenomas after castration. Evaluate 4 weeks after castration. If orchiectomy has not been performed in males, monitor additional tumor development. * Estrogen administration may be complicated by pancytopenia. If estrogen is administered, CBC and platelet count monthly. * Adenomas also respond well to radiotherapy. * Adenocarcinomas have a poor prognosis and are not likely to respond to hormonal manipulation. If resection is impossible, consider radiotherapy. * If perianal adenomas recur in castrated males or in females, consider adrenal glands (i.e., hyperadrenaocorticism) as a possible source of testosterone. Anal sac carcinoma * Prognosis for cure is poor. Local progression and metastasis to sublumbar lymph nodes common. Life expectancy is seldom more than 1 year without treatment, but quality of life may be good if hypercalcemia does not cause renal failure. * If completely resected, physical examination, abdominal radiography and biochemical analysis 1, 3, 6, 9 and 12 months after surgery is recommended to allow for early detection and therapuetic intervention. * If incomplete resection, measure tumor to determine if the neoplasm is responding to treatment. Careful monitoring of serum calcium and renal function necessary. SUGGESTED READING * The 5 Minute Veterinary Consult. By Tilley LP & Smith FWK. Lippincott, William & Wilkins, 2002. * Veterinary Oncology, From "The Practical Veterinarian Series". By Hahn KA. Butterworth-Heinemann Press, 2002. ============================================ SO WHAT DO WE DO AT GULF COAST? * After a complete clinical staging (examination, laboratory and imaging analyses) our preferred approach for managing dogs and cats with anal sac and perianal gland malignancies is the combination of surgical removal of the anal sac/perianal gland tumor followed by a combination of radiation to the anal region and draining sublumbar lymph nodes with chemotherapy (Adriamycin, Mitoxantrone or Carboplatin). * With surgical excision alone, recurrence and metastasis is expected within 1 year. * With surgical excision and radiation (to anal region and draining nodes), recurrence is not expected but metastasis to liver, lungs is expected in at least 50% of pets within 1 year. * With surgical excision, radiation therapy and adjuvant chemotherapy, recurrence is not expected and metastasis may be observed in <25% of pets at 1 year but in at least 50% at 2 years. * Without surgical excision but radiation therapy alone, regression of the lesion(s) is expected and quality of life is similar to those pets with surgical excision alone. * Without surgical excision but radiation therapy and chemotherapy, again, quality of life and outcome is similar to those in which surgical excision was performed. * In dogs and cats with grossly evident disease and signs of obstruction and surgical excision is difficult, palliative dosages of radiation are extremely helpful in the early recovery period. We hope this info helps and don't hesitate to call or email us at Gulf Coast Veterinary Oncology! Kevin Kevin A. Hahn, DVM, PhD Diplomate American College of Veterinary Internal Medicine (Oncology) & Overall Nice Guy Gulf Coast Veterinary Diagnostic Imaging & Oncology 1111 West Loop South, Suite 150, Houston, TX 77027 P: 713.693.1166 F: 713.693.1167 W: http://www.gcvs.com Email: mailto:drhahn@gcvs.com