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Compendium December 2006 (Vol 28, No 12)

Abstract Thoughts (December 2006)

by Joseph Harari, MS, DVM, DACVS

    Naan E, Kirpenstein J, Klooistra H: Results of thyroidectomy in 101 cats with hyperthyroidism. Vet Surg 35:287-293, 2006.

    Abstract: In this retrospective study of clinical cases from a veterinary teaching hospital in Holland, the outcome following surgical thyroidectomy in 101 hyperthyroid cats was described. The median age of the cats was 13 years, and most (62 cats) were treated before surgery with methimazole or atenolol for tachycardia. In 95 cases, thyroid scintigraphy revealed bilateral hyperplastic thyroid tissue in 86 cats. Six cats did not undergo scintigraphy before thyroidectomy in private practice and were referred for recurrence of signs. Ectopic thyroid tissue between the larynx and thoracic inlet was detected via scintigraphy in nine of 101 cases. Anesthesia was induced by propofol or medetomidine followed by isoflurane maintenance. Fentanyl was also used for analgesia during surgery and buprenorphine for postoperative pain relief. Surgery involved a modified intracapsular approach: All thyroid tissue was removed, except the capsule attached to the external parathyroid gland and the vascular supply to this gland. Ectopic tissue was removed following extension of the original incision. Two cats died within 3 days after surgery: one from laryngeal spasms, and the other from unknown cause(s). In 86 cases involving bilateral thyroidectomy and postoperative calcium determinations, five involved hypocalcemia, which resolved in all patients by 6 days after surgery. In 88 cases involving histologic evaluations, 85 involved benign adenomatous hyperplasia and three thyroid carcinoma. In a median follow-up of 13 months, five cats had recurrent hyperthyroidism, four of which had ectopic tissue before surgery. At the conclusion of the study, 57 cats were alive, with a mean survival of nearly 2 years, and 44 were dead, with a mean survival of 1 year. The authors concluded that surgical thyroidectomy was safe and useful in treating patients without ectopic hyperplastic tissue.

    Commentary: Hyperthyroidism due to benign hyperplastic tissue is a common endocrinopathy in middle-aged and older cats. Morbidity is high, and clinical signs are related to a hypermetabolic state and behavioral changes. Treatments are based on antithyroid medications, surgical resection of affected tissues, and/or radioactive iodine. Selection of a specific therapy is based on patient, client, and availability factors. In this clinical study, the authors describe positive results using medications to stabilize the patient preoperatively, minimally stressful anesthetic drugs and techniques, and a standard surgical procedure sparing parathyroid tissue. In addition, the use of scintigraphy preoperatively to determine location(s) of the lesion was critical to the outcome. The data from a large number of cases treated by the authors will aid clinicians and clients in determining diagnostic and treatment options as well as the prognosis for cats with this condition.

    Emergency Presentations Of Dogs With Suspected Neurologic Toxoplasmosis

    Tarlow JM, Rudloff E, Lichtenberger M, Kirby R: Emergency presentations of 4 dogs with suspected neurologic toxoplasmosis. J Vet Emerg Crit Care 15:119-127, 2005.

    Both dogs and cats can develop toxoplasmosis, which is usually associated with an immunocompromised state but not with neurologic signs. This retrospective study examined the clinical course and response to therapy of four dogs meeting inclusion criteria of confirmed toxoplasmosis plus neurologic or neuromuscular signs. These dogs (two golden and two Labrador retrievers; three neutered, one spayed; 4 to 6 years of age) had titers positive for Toxoplasma gondii with no other apparent cause of neurologic dysfunction. Data examined included signalment, presenting complaint, clinical and laboratory results, Toxoplasma titers, therapeutic course, and response to treatment.

    A tentative diagnosis of toxoplasmosis can be based on a fourfold or higher change in serial serum Toxoplasma titers, decreasing serum IgM titers plus concurrent increasing serum IgG titers, or positive cerebrospinal fluid titers. Neurologic signs were both central and peripheral; no consistent biochemical or hematologic abnormalities were seen. Clinical signs resolved after treatment with trimethoprim"sulfamethoxazole, although two dogs required a change to clindamycin after experiencing adverse effects.

    Key Findings:

    • Toxoplasmosis is an important differential diagnosis in dogs presenting with central or peripheral neurologic signs; Neospora caninum infection should be ruled out.
    • Animals can be immunocompetent.
    • Treatment with trimethoprim"sulfamethoxazole is preferred, but clindamycin may be used as a substitute if toxicosis occurs.
    NEXT: Letters — Questionable Differentials


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