Abstract
Radioactive Iodine Dose and Survival In Cats With Hyperthyroidism (2015–2020)
Joyce Chow, Joanna White
Small Animal Specialist Hospital, North Ryde, Australia
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Radioactive iodine (131I) is the preferred treatment for feline hyperthyroidism, but neither the optimal 131I dosing protocol nor consistent predictors of post-treatment azotaemia have been determined. The aims of the study were to evaluate the relationships between (1) 131I dose and survival and (2) pretreatment and post-treatment creatinine concentration.
Medical records of hyperthyroid cats treated with 131I at a referral hospital were reviewed. Information regarding signalment, body weight, pre- and post-treatment total thyroid hormone (TT4) and creatinine concentration, 131I dose and survival was collated. Median survival time (MST) was determined by the Kaplan–Meier method. Multivariable Cox proportional hazards analysis was used to identify factors associated with survival. Multivariable linear regression analysis was used to identify factors associated with post-treatment creatinine concentration.
One hundred and ninety-eight (79 male, 119 female) cats were treated for hyperthyroidism with 131I (median dose 138 MBq; interquartile range 92–168). MST was 1153 days (range 16–1871). Post-treatment creatinine (P <0.001) and age (P = 0.049) were significantly associated with survival. Every 10 µmol/l increase in post-treatment creatinine and every year increase in age was associated with a 1.07-fold (confidence interval [CI] 1.04–1.11) and 1.17-fold (CI 1.00–1.37) increase in the daily hazard of death, respectively. Pretreatment creatinine concentration was positively (P <0.001), and post-treatment TT4 was inversely (P <0.001), associated with post-treatment creatinine concentration.
131I dose was not directly associated with survival but 131I dosing strategies that minimise post-treatment hypothyroidism and azotaemia could improve patient survival.
Influence of Social Isolation on Feline Lower Urinary Tract Disease
Kayla Jackson, Kate Collins, Te Yeun Kim, Rebekah E Donaldson
Queensland Veterinary Specialists, Stafford Heights, QLD, Australia
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Feline idiopathic cystitis (FIC) and urethral obstruction (UO) are associated with environmental stress factors. The COVID-19 pandemic has restricted human movement and working behaviours; however, it is unknown if these restrictions have increased the risk of FIC or UO in cats.
Retrospective review of medical records from 8 February 2019 to 8 February 2021 documented total cat emergency cases (both primary accession and primary care veterinarian transfers). Cats were included in the FIC/UO group if they presented to the emergency department for lower urinary tract signs, and had urinalysis performed that supported a diagnosis of FIC. Cats were excluded from the group if they were diagnosed with FIC or UO previously, or with non-obstructive urinary tract infection on presentation. FIC and UO cases were compared between COVID-19 (2020) and pre-COVID-19 (2019) years using Fisher’s exact test and relative risk (RR) calculations.
Of 1477 cats presenting in 2019, 20 FIC and 42 UO patients were identified. One cat was excluded from the UO group as the obstruction developed secondarily in hospital. Of 2081 cats presenting in 2020, 43 FIC and 70 UO patients were identified. The risk of developing FIC (P = 0.122; RR 0.652, 95% confidence interval [CI] 0.387–1.096), UO (P = 0.382; RR 0.839, 95% CI 0.577–1.22) or either (P = 0.098; RR 0.773, 95% CI 0.572–1.044) was not significantly higher in 2020.
No clear association exists between COVID-19 movement restrictions and the incidence of FIC or UO. Further statistical analysis will include a larger control population and compare specific lockdown dates.
Phenobarbital-Induced Pseudolymphoma and Haematological Abnormalities in a Cat
Michelle Walton-Clark1, Victoria Travail2, Matthew Best1
1Eastcott Referrals, Swindon, Wiltshire, UK
2Hamilton Specialist Referrals, High Wycombe, Buckinghamshire, UK
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A 1.5-year-old neutered female domestic shorthair cat presented with lymphadenomegaly, hyperglobulinaemia and anaemia following 2 weeks of therapy with phenobarbital, 3 mg/kg PO q12h, for idiopathic epilepsy, following comprehensive investigations including MRI.
On presentation, the cat was quiet, alert and responsive. Physical examination revealed pale pink mucous membranes and peripheral lymphadenomegaly. Haematology showed a regenerative anaemia (haematocrit 19.3%, reticulocyte count 118.08 × 109/l) and saline agglutination was positive. Biochemistry showed a hyperglobulinaemia (61 g/l). Feline immunodeficiency virus antibody, feline leukaemia virus antigen and Haemoplasma species PCR were negative. Lymph node cytology showed changes consistent with reactive lymphoid hyperplasia; no atypical cells or infectious agents were seen. Phenobarbital-induced pseudolymphoma and immune-mediated anaemia were suspected. The packed cell volume decreased to 11% and a fresh whole blood transfusion was performed. Treatment with levetiracetam was commenced, while phenobarbital was discontinued. Complete resolution of the lymphadenopathy and anaemia was documented within 4 weeks.
Phenobarbital is commonly used as a first-line treatment for epilepsy in cats. Although there are limited case reports of phenobarbital-induced haematological changes and lymphadenomegaly, this combination of sequelae has not previously been reported in cats and is similar to the rare but significant syndrome in humans known as ‘anticonvulsant hypersensitivity syndrome’. Anticonvulsant hypersensitivities should be considered as a potentially serious, yet reversible, sequela to phenobarbital treatment that may be mistaken for more severe illness such as neoplasia.
Feline Pleural Effusion: Radiographic Signs and Clinical Parameters Predicting Disease Aetiology
Lily Hing Ting Hung1, Belinda Judith Hopper1, Alison Hillman2,3, Zoe Lenard1
1Animalius, Perth, Western Australia, Australia
2Ausvet, Fremantle, Australia
3Murdoch University, Perth, Australia
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The objectives of the study were to determine the prevalence of underlying conditions causing pleural effusion in cats, compare clinical parameters between the conditions and calculate the positive predictive values, negative predictive values, and the sensitivity and specificity of radiographic signs.
Data from 151 cats diagnosed with pleural effusion with known aetiologies were retrospectively analysed. Seventy-one patients’ thoracic radiographs were available for a prospective, blinded evaluation by two radiologists.
Congestive heart failure (52.3%) was the most common diagnosis, followed by neoplasia (21.9%), pyothorax (10.6%), idiopathic chylous effusion (5.3%), feline infectious peritonitis (1.3%) and cats with other, or multiple, diagnoses (total 9.3%). Cats with an enlarged cardiac silhouette had a high positive predictive value of congestive heart failure (73% and 81% for radiologists 1 and 2, respectively). Cats with congestive heart failure had significantly higher heart rates compared with cats with pyothorax (on average 27.1 beats per minute higher, P = 0.02). The presence of unilateral effusion was highly predictive of pyothorax (75%) for radiologist 1 and poorly predictive (20%) for radiologist 2. Mediastinal masses (100% and 83% for radiologists 1 and 2, respectively), pulmonary nodules (50% for both radiologists) and pulmonary masses (50% and 67% for radiologists 1 and 2, respectively) had moderate probabilities of neoplasia. The remainder of the radiographic variables were not informative predictors of underlying disease.
In our population of cats, congestive heart failure was the most common cause of pleural effusion. A radiographically enlarged cardiac silhouette, presence of a mediastinal mass and unilateral effusion may be useful predictors of aetiology.
✜ This abstract is an update of the version presented at the ANZCVS virtual conference.
