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Recent evidence in feline medicine and surgery

New Knowledge Summaries consider management of hyperthyroidism and stabilisation of coxofemoral dislocation

02 April 2019, at 9:30a.m.

RCVS Knowledge has recently published two Knowledge Summaries that may help vets undertake more evidence-based feline medicine and surgery. The first considers iodine-restricted diets for hyperthyroidism and the second asks which technique is best for managing coxofemoral dislocations.

Can iodine-restricted diets normalise serum total thyroxine (TT4) and subsequently improve clinical signs in cats with hyperthyroidism?

There is some evidence that iodine-restricted diets can help to renormalise serum TT4 in cats with hyperthyroidism, though this is not always effective and there is a lack of compelling evidence to suggest this is associated with a resolution of clinical signs in the long term.

Whilst there is limited literature investigating the efficacy of iodine-restricted diets as a treatment for feline hyperthyroidism, all the studies so far have documented a 100 percent improvement in serum TT4 when cats have been started on an iodine-restricted diet, though this did not always guarantee a return to euthyroid status.

A limitation of all the studies into this subject is the difficulty in maintaining and proving 100 percent compliance, as all the patients enrolled in the studies were client-owned and potentially allowed outdoor access.

There is a lack of consensus regarding the resolution of clinical signs. Documenting an improvement in clinical signs is difficult, given the subjective nature of the task, and made more complicated by the fact that the cats were only assessed by veterinarians at set intervals.

Further to this disparity amongst the literature, the limited number of studies and the limitations of those studies mean a prospective study with large sample size and lifelong follow-up would improve the evidence base greatly.

No cats were removed from any of the studies due to concerns about the safety of the diet, or as a result of any side effects, so it can be concluded at least that the diet is safe.

The full Knowledge Summary can be viewed here.

Author: Oliver Gilman

Reluxation rates following different techniques for open stabilisation of feline coxofemoral dislocations

There is currently insufficient evidence to identify if transarticular pinning or a toggle rod technique result in lower rates of reluxation following surgical management of craniodorsal coxofemoral luxations in cats.

Both transarticular pinning and toggling using the Arthrex Mini TightRope system with Arthrex FiberWire suture resulted in 0 percent reluxation rates at short-term radiographic follow-up. Longer-term follow-up of joints stabilised using transarticular pinning found 16.6 percent reluxation (2/13 joints) when radiographed at least six months after surgery.

Toggling using an IMEX toggle (IMEX Veterinary Inc.) and polydioxanone (PDS II, Ethicon) suture had a reluxation rate of 14 percent (2/14 joints) at 3.5 to 6 weeks after surgery.

It appears that reluxation rates for all three techniques compare favourably to generally quoted reluxation rates following open reduction and that the use of all reported techniques can be justified for these cases in cats.

It is important to consider if reluxation is the most clinically useful outcome measure. Long-term degenerative joint disease may be a more important clinical comparator between surgical techniques and more objective outcome measures such as measuring ground reaction force on pressure sensitive walkways could be considered.

In general, the studies fail to generate any descriptive rationale for the selection of one surgical procedure over another.

The full Knowledge Summary can be viewed here.

Author: Elly Russell