Concurrent thoracic pathology identified with radiology in hyperthyroid cats referred for radioiodine therapy

Objectives: Radioiodine (RAI) treatment for hyperthyroidism is becoming increasingly available in the UK. Pretreatment assessment is commonly performed, as patient handling is limited once RAI has been administered. The aims of this study were to determine the prevalence of thoracic pathology using thoracic radiography in hyperthyroid cats referred for RAI treatment and to determine the value of this technique pretreatment. Methods: The hospital databases were searched for hyperthyroid cats referred for RAI treatment at the Feline Centre, Langford Vets, between January 2012 and July 2016. Radiographs were reviewed by Diplomates of the European College of Veterinary Diagnostic Imaging at the time of treatment and each set of radiographs was subsequently reviewed by one radiologist for the study. Cardiorespiratory signs were recorded, if present, and any change in treatment plan or suitability for RAI treatment was documented. Results: Two hundred and fifty-two cats were included in the study. Thoracic pathology was identified in 77% (n = 194/252) of the cats, of which 59% (n = 115/194) had pulmonary abnormalities with bronchial and bronchointerstitial patterns most frequently; 57% (n = 111/194) had skeletal abnormalities and 43% (n = 84/194) had cardiac abnormalities, with mild-to-moderate cardiomegaly most prevalent. Other abnormalities included sternal lymphadenomegaly (7%; n = 13/194), mediastinal pathology (3%; n = 5/194), oesophageal pathology (2%; n = 4/194) and pleural space disease (0.5%; n = 1/194).Twelve cases (6%) had a change in their treatment plan as a result of thoracic radiographic abnormalities, of which five subsequently underwent RAI treatment. Conclusions and relevance: A low prevalence of significant thoracic pathology was identified on radiographs in hyperthyroid cats referred for RAI treatment. Incidental thoracic abnormalities were found much more commonly; hence, results of thoracic radiology need to be combined with the clinical picture, to decide whether further investigations or alterations to the treatment plan are required pre-RAI.