Cynthia R. Ward

Flexible endoscopy in small animals.

Flexible endoscopy is a valuable tool for the diagnosis of many small animal digestive tract diseases. This article provides a basic introduction to small animal gastrointestinal endoscopy including its diagnostic advantages as well as its limitations and complications. Although proficiency in endoscopic techniques can only be obtained through many hours of practice, this article should also encourage and stimulate the novice endoscopist.

2016 AAFP Guidelines for the Management of Feline Hyperthyroidism

Clinical context: Since 1979 and 1980 when the first reports of clinical feline hyperthyroidism (FHT) appeared in the literature, our understanding of the disease has evolved tremendously. Initially, FHT was a disease that only referral clinicians treated. Now it is a disease that primary clinicians routinely manage. Inclusion of the measurement of total thyroxine concentration in senior wellness panels, as well as in diagnostic work-ups for sick cats, now enables diagnosis of the condition long before the cat becomes the classic scrawny, unkempt, agitated patient with a bulge in its neck. However, earlier recognition of the problem has given rise to several related questions: how to recognize the health significance of the early presentations of the disease; how early to treat the disease; whether to treat FHT when comorbid conditions are present; and how to manage comorbid conditions such as chronic kidney disease and cardiac disease with treatment of FHT. The 2016 AAFP Guidelines for the Management of Feline Hyperthyroidism (hereafter referred to as the Guidelines) will shed light on these questions for the general practitioner and suggest when referral may benefit the cat. Scope: The Guidelines explain FHT as a primary disease process with compounding factors, and provide a concise explanation of what we know to be true about the etiology and pathogenesis of the disease. The Guidelines also: Distill the current research literature into simple recommendations for testing sequences that will avoid misdiagnosis and separate an FHT diagnosis into six clinical categories with associated management strategies. Emphasize the importance of treating all hyperthyroid cats, regardless of comorbidities, and outline the currently available treatments for the disease. Explain how to monitor the treated cat to help avoid exacerbating comorbid diseases. Dispel some of the myths surrounding certain aspects of FHT and replace them with an evidence-based narrative that veterinarians and their practice teams can apply to feline patients and communicate to their owners. Evidence base: To help ensure better case outcomes, the Guidelines reflect currently available, evidenced-based knowledge. If research is lacking, or if a consensus does not exist, the expert panel of authors has made recommendations based on their extensive, cumulative clinical experience.

Familial Insulin-Dependent Diabetes Mellitus in Samoyed Dogs

Five adult Samoyed dogs from two unrelated litters were diagnosed with diabetes mellitus. Two full-sibling male dogs (Family A) were raised in the same household. The other three dogs, two female and one male, were also full siblings (Family B) raised in different households. All five dogs developed polyuria and polydipsia and demonstrated fasting hyperglycemia and glucosuria. Diabetes mellitus was diagnosed in all five dogs and responded to appropriate therapy with insulin. The occurrence of insulin-dependent diabetes mellitus in multiple, closely related Samoyed dogs suggests a familial predisposition in this breed.

Effect of Trilostane and Mitotane on Aldosterone Secretory Reserve in Dogs with Pituitary‐Dependent Hyperadrenocorticism

Background Maximal aldosterone secretion in healthy dogs occurs 30 minutes postadrenocorticotropin (ACTH; 5 μg/kg IV) stimulation. The effect of trilostane and mitotane on aldosterone at that time is unknown. Objectives To assess the effect of trilostane and mitotane in dogs with pituitary‐dependent hyperadrenocorticism on aldosterone secretory reserve. To determine if aldosterone concentration correlates with electrolyte concentrations. Animals Serum collected from 79 client‐owned dogs and 33 stored samples. Methods Client‐owned dogs had ACTH stimulation tests with cortisol concentrations measured at 0 and 60 minutes and aldosterone concentrations measured at 0, 30, and 60 minutes. Stored samples had aldosterone concentrations measured at 0 and 60 minutes. Ten historical clinically healthy controls were included. All had basal sodium and potassium concentrations measured. Results The aldosterone concentrations in the mitotane‐ and trilostane‐treated dogs at 30 and 60 minutes post‐ACTH were significantly lower than in clinically healthy dogs; no significant difference was detected in aldosterone concentration between 30 and 60 minutes in treated dogs. However, a significantly higher percentage of dogs had decreased aldosterone secretory reserve detected at 30 minutes than at 60 minutes. At 30 minutes, decreased secretory reserve was detected in 49% and 78% of trilostane‐ and mitotane‐treated dogs, respectively. No correlation was detected between aldosterone and serum electrolyte concentrations. Conclusions and Clinical Importance Decreased aldosterone secretory reserve is common in trilostane‐ and mitotane‐treated dogs; it cannot be predicted by measurement of serum electrolyte concentrations. Aldosterone concentration at 30 minutes post‐ACTH stimulation identifies more dogs with decreased aldosterone secretory reserve than conventional testing at 60 minutes.

Evaluation of activation of G proteins in response to thyroid stimulating hormone in thyroid gland cells from euthyroid and hyperthyroid cats

OBJECTIVE To evaluate alterations in ligand-stimulated activity of G proteins in thyroid gland cells of hyperthyroid cats. SAMPLE POPULATION Membranes of thyroid gland cells isolated from 5 hyperthyroid cats and 3 age-matched euthyroid (control) cats immediately after the cats were euthanatized. PROCEDURES Isolated thyroid cell membranes were treated with thyroid-stimulating hormone (TSH), and activation of G protein was quantified by measurement of the binding of guanosine triphosphate gamma labeled with sulfur 35 (GTPgamma(35)S). The separate effects of G-protein inhibitory (G(i)) and G-protein stimulatory (G(s)) proteins were determined by the use of pertussis toxin and cholera toxin, respectively. RESULTS Thyroid cell membranes from hyperthyroid cats had higher basal GTPgamma(35)S binding than did thyroid cell membranes from euthyroid cats. Thyroid cell membranes from hyperthyroid and euthyroid cats had a concentration-dependent increase in TSH-stimulated GTPgamma(35)S binding over the TSH range of 0 to 100 mU/mL, with maximal activity at 1 to 100 mU/mL for both. The percentage increase in GTPgamma(35)S binding stimulated by TSH was similar in magnitude between the membranes from hyperthyroid and euthyroid cats. The TSH-stimulated activation of G(s) and G(i) was not different between euthyroid and hyperthyroid cats. CONCLUSIONS AND CLINICAL RELEVANCE Ligand-stimulated activation of G proteins was the same in thyroid cell membranes obtained from hyperthyroid and euthyroid cats. Therefore, alterations in inherent G(s) or G(i) activities did not appear to be part of the pathogenesis of hyperthyroidism in cats.

DIABETES MELLITUS, HYPERADRENOCORTICISM, AND HYPOTHYROIDISM IN A DOG

An unusual combination of three endocrinopathies found in one dog is described. A six-year-old, spayed female, mixed-breed dog presented with polyuria, polydipsia, polyphagia, and weight loss. She was diagnosed with diabetes mellitus but was suspected of having insulin resistance and was diagnosed subsequently with hyperadrenocorticism. Persistent hypercholesterolemia led to the suspicion and eventual diagnosis of hypothyroidism. The dog has responded well to medical therapy, and her clinical signs and biochemical changes have resolved. A literature search did not identify a similar-reported polyendocrinopathy.

Dermoid cysts presenting as enlarged thyroid glands in a cat.

A 5-year-old spayed female cat was evaluated for hyperthyroidism based on an elevated free thyroxine (T4) measurement and bilaterally enlarged symmetric subcutaneous masses in the area of the thyroid glands. Physical examination revealed bilateral subcutaneous masses on either side of the cervical trachea. Blood was obtained for serum biochemical profile and thyroid function analysis. Mild hyperalbuminemia, mild hypercalcemia, and mildly increased alanine aminotransferase activity were identified. Serum concentrations of total and free thyroxine were within the reference interval. Cytologic analysis of fine-needle aspirates from one of the masses was suspicious for neoplasia. Nuclear scintigraphy revealed no abnormalities. Surgically obtained excisional biopsies of both masses were submitted for histopathology and diagnosed as bilateral dermoid cysts. After excisional biopsy, the patient recovered without incident. The histopathologic diagnosis of completely excised bilateral dermoid cysts indicated that no further medical or surgical intervention was required. This is the first report of a cat presenting with bilateral dermoid cysts in the area of the thyroid glands. Histopathologic examination was necessary to make a definitive diagnosis. Practitioners should include cysts in their list of differential diagnoses for ventral neck masses in cats.

Comparison of 2 Doses for ACTH Stimulation Testing in Dogs Suspected of or Treated for Hyperadrenocorticism

Background Lowering the cosyntropin dose needed for ACTH stimulation would make the test more economical. Objectives To compare the cortisol response to 1 and 5 μg/kg cosyntropin IV in dogs being screened for hyperadrenocorticism (HAC) and in dogs receiving trilostane or mitotane for pituitary‐dependent HAC. Animals Healthy dogs (n = 10); client‐owned dogs suspected of having HAC (n = 39) or being treated for pituitary‐dependent HAC with mitotane (n = 12) or trilostane (n = 15). Procedures In this prospective study, healthy dogs had consecutive ACTH stimulation tests to ensure 2 tests could be performed in sequence. For the first test, cosyntropin (1 μg/kg IV) was administered; the second test was initiated 4 hours after the start of the first (5 μg/kg cosyntropin IV). Dogs suspected of having HAC or being treated with mitotane were tested as the healthy dogs. Dogs receiving trilostane treatment were tested on consecutive days at the same time post pill using the low dose on day 1. Results In dogs being treated with mitotane or trilostane, the 2 doses were pharmacodynamically equivalent (90% confidence interval, 85.1–108.2%; P = 0.014). However, in dogs suspected of having HAC, the doses were not pharmacodynamically equivalent (90% confidence interval, 73.2–92.8%; P = 0.37); furthermore, in 23% of the dogs, clinical interpretation of test results was different between the doses. Conclusions and Clinical Relevance For dogs suspected of having HAC, 5 μg/kg cosyntropin IV is still recommended for ACTH stimulation testing. For dogs receiving mitotane or trilostane treatment, a dose of 1 μg/kg cosyntropin IV can be used.

Effect of dexamethasone or synthetic ACTH administration on endogenous ACTH concentrations in healthy dogs

OBJECTIVE To determine the effects of dexamethasone or synthetic ACTH administration on endogenous ACTH concentrations in healthy dogs. ANIMALS 10 healthy neutered dogs. PROCEDURES Each dog received dexamethasone (0.01 mg/kg), synthetic ACTH (5 μg/kg), or saline (0.9% NaCl) solution (0.5 mL) IV at intervals of ≥ 30 days. Plasma endogenous ACTH concentrations were measured before (baseline; time 0) and 1, 8, 12, and 24 hours after drug administration; serum cortisol concentrations were measured before and 1 hour after synthetic ACTH and saline solution administration and 8 hours after dexamethasone administration. RESULTS Analysis of serum cortisol concentrations confirmed effects of drug administration. Dexamethasone significantly decreased the endogenous ACTH concentration from the baseline value at both 8 and 12 hours. Synthetic ACTH administration significantly decreased the endogenous ACTH concentration from the baseline value at 8 hours. Saline solution administration had no significant effect on endogenous ACTH concentration. CONCLUSIONS AND CLINICAL RELEVANCE Dexamethasone and synthetic ACTH administered IV at doses used routinely during testing for hyperadrenocorticism caused significant but transient reductions of endogenous ACTH concentrations in healthy dogs. Thus, a 2-hour washout period following ACTH stimulation testing before collection of samples for measurement of the endogenous ACTH concentration may be insufficient. Although this effect has not been verified in dogs with hyperadrenocorticism, these data suggested that samples for measurement of endogenous ACTH concentrations should be obtained before or > 8 hours after initiation of an ACTH stimulation test or before or > 12 hours after the start of a low-dose dexamethasone suppression test.