Angie Hibbert

Scintigraphic findings in 120 hyperthyroid cats

The aim of this study was to characterise the scintigraphic findings in a large population of hyperthyroid cats in order to determine the location of thyroid pathology in newly diagnosed hyperthyroid cats and those that had previously undergone thyroidectomy. A specific aim was to identify the proportion of cats with ectopic hyperfunctional thyroid tissue and characterise the scintigraphic and clinical features of this subset of cats. Nearly one in five hyperthyroid cats was identified to have multiple areas of hyperfunctional thyroid tissue and/or intrathoracic hyperfunctional thyroid tissue where surgical thyroidectomy would not be curative. In addition, this study demonstrated that scintigraphy cannot reliably distinguish between thyroid carcinoma and adenoma. Owners should always be warned about the possibility of ectopic thyroid tissue before thyroidectomy is performed. In this study, intrathoracic hyperfunctional thyroid tissue and multiple areas of increased radionuclide uptake (IRU) were a common feature of benign thyroid disease and responded well to treatment with low dose radioiodine.

Feline thyroid carcinoma: diagnosis and response to high-dose radioactive iodine treatment

This study reports the scintigraphy, histopathology, sole treatment with high-dose radioactive iodine and outcome of eight cases of feline thyroid carcinoma. Scintigraphic findings were variable and in 7/8 cases scintigraphic features could not reliably distinguish whether the thyroid tissue was malignant. Histopathology revealed typical criteria of malignancy in all cases, with mitotic activity described most frequently (7/8 cases), followed by infiltration of local tissues (4/8 cases). Cellular pleomorphism was infrequently observed. Single high-dose (1100 MBq I131) radioiodine therapy was successful in 6/8 cases, with complete resolution of hyperthyroidism, and was associated with prolonged survival times (181–2381 days). Sole treatment with high-dose radioiodine is a safe and effective treatment for functional thyroid carcinoma. The prognosis for feline thyroid carcinoma successfully treated with radioiodine is good, with extended survival times commonly achieved.

Best practice for the pharmacological management of hyperthyroid cats with antithyroid drugs

Pharmacological management of feline hyperthyroidism offers a practical treatment option for many hyperthyroid cats. Two drugs have been licensed for cats in the last decade: methimazole and its pro-drug carbimazole. On the basis of current evidence and available tablet sizes, starting doses of 2·5 mg methimazole twice a day and 10 to 15 mg once a day for the sustained release formulation of carbimazole are recommended. These doses should then be titrated to effect in order to obtain circulating total thyroxine (TT4) concentrations in the lower half of the reference interval. Treated cases should be monitored for side-effects, especially during the first months of treatment. Some side-effects may require discontinuation of treatment. At each monitoring visit, clinical condition and quality of life should also be evaluated, with special attention to possible development of azotaemia, hypertension and iatrogenic hypothyroidism. When euthyroidism has been achieved, monitoring visits are recommended after 1 month, 3 months and biannually thereafter. Cats with pre-existing azotaemia have shorter survival times. However, development of mild azotaemia during the initial course of treatment, unless associated with hypothyroidism, does not appear to decrease survival time. The long-term effects of chronic medical management require further study.

Serum cobalamin concentrations in cats with gastrointestinal signs: correlation with histopathological findings and duration of clinical signs

The aims of this study were to investigate the prevalence of hypocobalaminaemia in UK cats presented for referral investigation of gastrointestinal signs and to ascertain whether the duration of clinical signs or severity of disease (based on WSAVA Gastrointestinal Standardization histopathological grading) related to cobalamin concentration. The study population comprised 39 cats, of which 11 (28.2%) had hypocobalaminaemia. Eight of these cats were diagnosed with a single cause of gastrointestinal signs: intestinal inflammation (five); alimentary lymphoma (two); and cholangitis (one). Two or more concurrent diseases were diagnosed in the three remaining cases. Alimentary lymphoma and the most severe grade of histological intestinal inflammation were associated most commonly with concurrent hypocobalaminaemia, but there was no statistically significant correlation between serum cobalamin concentrations and histopathological score or duration of clinical signs.

A survey of owners' perceptions and experiences of radioiodine treatment of feline hyperthyroidism in the UK

The efficacy of radioiodine treatment of feline hyperthyroidism is well established; however, limited information is known about owners’ perceptions or experiences of radioiodine. This study aimed to examine factors that influence owner treatment choices and their opinions following radioiodine. Surveys were sent to owners of cats referred for radioiodine treatment between 2002 and 2011 (radioiodine group; 264 cats) and owners of non-radioiodine-treated hyperthyroid cats seen at first-opinion practices (control group; 199 cats). The response rate was 67.0% (310 returned: 175 radioiodine, 135 control). Of 135 controls, 72 (53.3%) were unaware of radioiodine as a treatment option. Owners of cats ⩾15 years old and uninsured cats were less likely to pursue radioiodine. Cost of treatment, travel distance, potential human or animal health risks and waiting periods for radioiodine had a low impact on owners’ treatment choice. Owners reported a moderate level of concern about treatment hospitalisation length, which included (158 respondents) the possibility of the cat being unhappy 130 (82.3%), owner missing the cat 102 (64.6%), inappetence 50 (31.6%), other pets missing the cat 32 (20.3%), development of co-morbid disease 28 (17.7%) and side effects 25 (15.8%). Owners assessed their cat’s quality of life on a scale of 1 (very poor) to 10 (excellent), as 4 (4) (median [interquartile range]) pre-radioiodine (134 respondents) and 9 (2) post-radioiodine (131 respondents). Of 132 respondents, 121 (91.7%) were happy with their decision to choose radioiodine. The results of this questionnaire may assist veterinarians in addressing common owner concerns when discussing radioiodine as a treatment option for hyperthyroidism.

Medical management and monitoring of the hyperthyroid cat: a survey of UK general practitioners

Feline hyperthyroidism is commonly diagnosed in general practice. This study assessed the opinions and experiences of UK general practitioners (GPs) regarding the management of feline hyperthyroidism. This included an evaluation of preferred treatment modalities and the monitoring of medically treated cats in relation to thyroxine (T4) level, co-morbid disease and adverse drug reactions. Six hundred and three GPs completed an online questionnaire comprising 34 questions. Oral medication was the most commonly preferred treatment option (65.7% of respondents), followed by thyroidectomy (27.5%) and then radioiodine (5.5%). When cost of treatment was eliminated as a consideration factor, significantly more respondents selected radioiodine (40.5%, P <0.001). Concerning target total T4 levels during medical management, 48.4% aimed for the lower half of the reference interval (RI), 32.3% anywhere within RI, 13.1% within the top half of RI and 0.5% above the RI; 3.4% evaluated efficacy by physical assessment only. In the presence of chronic kidney disease (CKD) respondents were significantly more likely to target total T4 levels within the upper half of the RI (40.3%) or above it (9.8%) when compared with targets for routine cases (P <0.001). Assessment for unmasking of CKD after initiating treatment or for hypertension was not consistently performed. Variability in monitoring strategies may result in CKD and hypertension remaining undetected, inadequate suppression of T4 levels in cats with concurrent CKD and delayed recognition of potentially significant haematological abnormalities.

Use of cefovecin in a UK population of cats attending first-opinion practices as recorded in electronic health records

Objectives The objective was to use electronic health records to describe the use of cefovecin (Convenia; Zoetis UK), a third-generation long-acting injectable antimicrobial, in a UK population of cats attending first-opinion practices, and to compare the use of Convenia with the licensed uses described on the UK Convenia datasheet. Methods Data were obtained as an Excel database from the Small Animal Veterinary Surveillance Network for all feline consultations containing the word Convenia and/or cefovecin from 1 September 2012 to 23 September 2013 inclusive. Entries were classified according to body system treated, confirmation or suspicion of an abscess, evidence of microbiological evaluation being performed, any concurrent therapies given and whether any reason was given for use of Convenia over alternative antimicrobials. Data were exported to IBM SPSS Statistics and descriptive analysis performed. Results In total, 1148 entries were analysed. The most common body system treated was skin in 553 (48.2%) entries, then urinary (n = 157; 13.7%) and respiratory (n = 112; 9.8%). Microbiological evaluation was recorded in 193 (16.8%) entries, with visible purulent material most commonly cited (in 147 [12.8%] entries). A reason for prescribing Convenia over alternative antimicrobials was given in 138 (12.0%) entries; the most cited was an inability to orally medicate the cat in 77 (55.8%) of these entries. Excluding 131 entries where no body system or multiple body systems were described, the use of Convenia complied with a licensed use in the UK datasheet in 710 (69.8%) of 1017 entries. Conclusions and relevance Most administrations were licensed uses; however, most entries did not describe any microbiological evaluation, or a reason for prescribing Convenia over alternative antimicrobials. Further education of the public and the veterinary profession is needed to promote antimicrobial stewardship in the UK. Health records provide a valuable tool with which to monitor, both locally and at scale, the use of important therapeutics like antimicrobials. Information relevant to decision-making should be recorded in individual animal health records.

Clinicopathological features and comorbidities of cats with mild, moderate or severe hyperthyroidism: a radioiodine referral population:

Objectives This study sought to explore the clinicopathological features and comorbidities of cats with mild, moderate and severe hyperthyroidism in a radioiodine referral population. Methods Medical records were reviewed, along with results of serum biochemistry, urinalysis, systolic blood pressure and diagnostic imaging performed at the time of radioiodine referral. Cats were grouped by total thyroxine (TT4) levels as mildly (TT4 60.1–124.9 nmol/l), moderately (TT4 125–250 nmol/l) or severely (TT4 >250 nmol/l) hyperthyroid at the time of diagnosis and referral. Results Thirty percent (42/140) of the cats were <10 years old at diagnosis. In 24.3% (34/140), hyperthyroidism was diagnosed incidentally. The time between diagnosis and referral for radioiodine was significantly longer in cats with severe hyperthyroidism at the time of referral (P = 0.004). An increase in severity group between the time of diagnosis and referral occurred in 38.6% (54/140) of cats. At referral, 54.3% (25/46) of cats with mild, 66.7% (42/63) with moderate and 80.6% (25/31) with severe hyperthyroidism were unstable despite ongoing medical or dietary management. The prevalence of cardiac abnormalities was significantly increased in cats with severe hyperthyroidism (P = 0.014) compared with those with mild or moderate hyperthyroidism. There was no significant difference in the likelihood of renal disease (P = 0.708) or hypertension (P = 0.328) between the groups. Conclusions and relevance Incidental diagnosis of hyperthyroidism occurs commonly, potentially owing to increased disease screening. Cats with severe hyperthyroidism at referral were more likely to be chronically hyperthyroid with a history of poor stabilisation. This subset of patients was significantly more likely to have cardiac abnormalities. Thyrotoxic cardiomyopathy may ultimately affect patient suitability for curative treatments (radioiodine or thyroidectomy) owing to higher anaesthetic risks and potential for decompensation into congestive heart failure with the stress of travel and hospitalisation. Curative therapy should be considered before the development of severe hyperthyroidism.

Vitamin D toxicity of dietary origin in cats fed a natural complementary kitten food

Case series summary This case series describes two young sibling cats and an additional unrelated cat, from two separate households, that developed hypercalcaemia associated with hypervitaminosis D. Excessive vitamin D concentrations were identified in a natural complementary tinned kitten food that was fed to all three cats as part of their diet. In one of the cases, there was clinical evidence of soft tissue mineralisation. The hypercalcaemia and soft tissue mineralisation resolved following withdrawal of the affected food and medical management of the hypercalcaemia. Relevance and novel information This case series demonstrates the importance of obtaining a thorough dietary history in patients presenting with hypercalcaemia and the measurement of vitamin D metabolites when investigating such cases. Complementary foods may have the potential to induce nutritional toxicity even when fed with complete, nutritionally balanced diets.

The Flat Cat 1. A logical and practical approach to management of this challenging presentation

Aim: Detailed information regarding the causes and treatment of acute collapse in the cat can be difficult to locate in a single published source. This two-part review aims to provide a logical approach to the clinical assessment and stabilisation of the critically ill collapsed cat. Practical relevance: Cats are particularly challenging when presented as emergency patients, often in the later stages of an illness or with a vague history and non-specific signs. The nuances of the critically ill cat are considered, especially for shock and its management. Clinical challenges: Shocked cats do not present in the classic stages typically seen in dogs, and the signs are more subtle. Therefore, the clinician must consider whether physical parameters are appropriate for the state and environment of the patient; for example, a normal heart rate in a shocked cat would be considered inappropriate. Audience: This review is directed at any veterinarian working with feline patients, and particularly those dealing with emergencies on a regular basis. Evidence base: There is an extensive body of published literature, both original studies and textbook chapters, pertaining to the causes and treatment of collapse in the cat. In this article the authors draw on information from original publications, reviews and their clinical experience to provide practical guidance to assist in the emergency setting.