Introduction
Radioactive iodine therapy ( RAIT ) is becoming increasingly popular among cat owners for the treatment of their hyperthyroid cat . With a curative rate of ̴95 % after a single dose , it is the preferred treatment for feline hyperthyroidism ( FHT ) [ 1 ] . Adverse effects are uncommon ; iatrogenic hypothyroidism ( 2 %) and failure to achieve euthyroidism with a single dose ( 4 – 5 %) are the most commonly reported [ 1 – 3 ] . For some cases , barriers exist to treatment , including the suitability of RAIT for the cat , the cost of treatment , the need to isolate the cat and the availability of specialised treatment facilities .
Suitability for treatment
Whether or not RAIT is appropriate depends on factors such as a cat ' s overall health status , the time since diagnosis and the cat ' s age . Comorbidities such as earlystage chronic kidney disease ( CKD ) ( IRIS stages I – II ) and non-symptomatic hypertrophic cardiomyopathy ( HCM ) are not definitive contraindications for treatment , but the cat must be stable enough to undergo a week of isolation in the clinic [ 4 ] . Medical interventions would expose veterinary personnel to additional radiation and cats ideally should not leave isolation prematurely . This clinic does not provide any other veterinary treatment and is not set up for emergencies , so transport to a nearby emergency centre would be required if a cat ' s health deteriorated during the isolation period .
Cat owners also need to weigh up the advantages and disadvantages of RAIT versus other treatment options , particularly if their cat has comorbidities that alter life expectancy , such as symptomatic HCM or IRIS stages III – IV CKD . These cats could still receive RAIT but their quality of life could possibly be better maintained with medical management instead ; the latter might also be a more realistic financial option for some clients . If a client ' s primary goal of RAIT is to avoid the need for medicating their cat , they should be made aware that other health conditions requiring medication could still occur as their cat ages .
Advanced age (> 15 years ) is not a contraindication for RAIT but the cumulative cost of medical management could be less expensive than the upfront cost of RAIT . The progression of benign disease to thyroid carcinoma with non-curative treatments and the possibility of developing another thyroid carcinoma following successful RAIT are also considerations . The decision is therefore not always as simple as it might first appear and is based on many factors , including the client ' s values and preferences and the cat ' s anticipated life expectancy , comorbidities and overall health , which in many cases is impossible to establish in advance . Therefore , there is an element of luck involved when making the commitment to treat with RAIT .
The decision whether to treat a cat with RAIT should be made following discussions between the primary veterinary team and the client , the primary veterinary surgeon ( VS ) and the referral VS , and the referral VS and the client . Prior to this , a full history and health assessment must be completed and the results communicated to the client . Veterinary nurses ( VNs ) in primary practice are often approached by clients for advice after they have spoken to the VS . The VN cannot replace the expertise of the VS or make decisions for the client , but a sound knowledge of the RAIT process can assist the VN in clarifying information provided by the VS . This can help the client to make an informed decision about what is best for their cat and their circumstances .
One of the most concerning aspects of RAIT for clients is the need for their cat to be isolated . The isolation period varies depending on where treatment is taking place . At this clinic , isolation lasts 7 days for most cats . This is followed by a further 2-week period of restricted contact at home , including not allowing the cat to sleep in the same room as humans and minimal cuddle time with the cat . The VN has an important role in clarifying the client ' s concerns and providing information about the isolation experience and how cat welfare is maintained during this time , as well as making suggestions for altering the home environment to ensure everyone remains safe when the cat is discharged .
Pre-RAIT requirements
All pre-treatment diagnostics are conducted by the primary veterinary clinic . This includes a full blood panel and urinalysis , with symmetric dimethylarginine ( SDMA ) and total thyroxine ( TT4 ) measurement , from the time of initial FHT diagnosis until referral . It is well acknowledged that treating FHT can unmask pre-existing CKD . The alleviation of clinical signs of FHT , such as hypertension and increased cardiac output due to tachycardia , leads to a reduction in glomerular filtration rate and reveals the actual renal blood parameters .
At times , a newly diagnosed cat might be treated with anti-thyroid medication for 4 weeks , with TT4 and renal parameters ( including SDMA and urine specific gravity ) being retested prior to RAIT , in order to gauge response to treatment and identify potential renal comorbidity .
RAIT is most successful in newly diagnosed cats , those with TT4 < 100 nmol / l , cats without renal or cardiac comorbidities and cats that are physiologically stable [ 1 , 3 ] . The length of time between the diagnosis of FHT and RAIT can affect the dose required and the success of treatment . Abnormal thyroid cells can become malignant over time ( thyroid carcinoma ), which necessitates a dose of radioactive iodine ( RAI ) 3 – 10 times that administered to cats with non-malignant tumours [ 4 ] . These cats have a higher risk of developing iatrogenic hypothyroidism posttreatment , due to the increased dose .
42 Veterinary Nursing Journal