29 Aug 2023
Kit Sturgess discusses how to diagnose, treat and manage this increasingly common condition in UK cats and dogs.
Kit Sturgess
Job Title
Image © Africa Studio / Adobe Stock
It has been slightly more than 100 years since insulin was first used to manage diabetes mellitus (DM) in humans, and we are still struggling with understanding and managing the problem.
With nearly half a million articles having been written and 148 diabetes-related journals, you would have thought we would be better at controlling the most common endocrinopathy in people and dogs, and the second most common in cats.
The veterinary literature, about 3,800 articles, is only a fraction of that in humans, but distilling that into practical advice and understanding of where we are today is still a challenge. Diabetes is estimated to affect about 0.36% of dogs (Mattin et al, 2014) and 0.43% of cats (O’Neill et al, 2016), meaning approximately 100,000 pets in the UK are diabetic.
The incidence of diabetes is rising in both people and pets. The author has a few “rules” on case management, but given this prevalence, every polyuric/polydipsic (PU/PD) patient and emergency case has a blood glucose measured as an early part of their investigation.
Clearly, not all hyperglycaemic patients – especially cats – will be diabetic (Panel 1), but it means that manageable disease will not be missed, particularly those new diabetics (around 15% of cases) that present with diabetic ketoacidosis (DKA).
A recent article in Veterinary Clinics of North America: Small Animal Practice (Gilor and Graves, 2023) provides a comprehensive review of the current state of knowledge. Understanding of DM in cats and dogs is evolving, and a number of significant changes made in recent years are driving changes in the ways of approaching the management of DM in general practice.
Around 85% of patients present with “typical” signs of diabetes; signs are often more subtle in cats. The three most common signs in cats and dogs are the following:
These signs may be accompanied by lethargy and depression with reduced exercise tolerance in dogs.
PU/PD may be less noticeable in cats, as some will drink and urinate outside. In indoor cats, PU may not be seen as more frequent urination, but by larger volume being passed, with owners noticing this as a bigger clump of wet litter having to be removed – this may not be something the owners have consciously realised; therefore, it should be asked as a specific historical question.
In dogs – especially where an outside water source is present – the owners may not notice PD, but report that they are being woken up more frequently at night to let the dog out to urinate. Sometimes – especially in bitches – owners may report urinary incontinence; therefore, it is essential to at least perform a urine specific gravity and dipstick test on all incontinent patients, although – as with hyperglycaemia – glucosuria alone does not make a diagnosis of DM (Panel 2).
Weight loss and polyphagia may be missed or ignored by the owner, with polyphagia being seen as a sign of good health. Similarly, in overweight dogs or cats, a sudden loss of weight – especially if the owner is making attempts at dieting – is seen in a positive light.
Less commonly, DM can present as:
Presenting signs of DKA and HHS patients are variable, in these cases, with diabetes not necessarily being high up on the differential list (Table 1); hence, the importance of checking blood glucose.
| Table 1. Presenting signs of diabetic ketoacidosis and hyperglycaemic hyperosmolar syndrome | |||
|---|---|---|---|
| Diabetic ketoacidosis | Hyperglycaemic hyperosmolar syndrome | ||
| Common signs | Uncommon signs | Common signs | Uncommon signs |
|
Historic PU/PD Lethargy Inappetence Anorexia Adipsia Vomiting with or without diarrhoea Weight loss |
Underweight Dehydrated Icterus Hepatomegaly |
Ataxia Weakness Depression Respiratory problems Neurologic signs – circling, pacing, unresponsive |
Overweight Moderate to severe dehydration Respiratory compromise Hypothermia Shock |
For the majority of patients, the mainstay of diabetes management remains insulin. Broadly, three types of insulin are regularly used: biphasic lente insulin, protamine zinc insulin and long-acting recombinant human insulins (for example, glargine or detemir).
Neutral (soluble) insulins, while important in managing DKA, are not generally used for day-to-day management of cats or dogs with DM. Recently, once-weekly insulins have been developed for people, with limited work undertaken in dogs (Hulsebosch et al, 2022) and cats (Gilor et al, 2021).
Choice of insulin should be based on a number of factors. Most diabetic patients are probably better controlled on twice-daily insulin. For owners for whom practical or patient factors make once-daily insulin the better option, then longer acting insulins are necessary. For cats, this usually requires glargine or detemir; for dogs, either protamine zinc, glargine or detemir. It is unusual to be able to stabilise a patient using biphasic lente insulin once daily.
Feeding regime can also influence insulin choice. For diabetics who are not portion fed (for example, cats that graze on dry food through the day), insulin with more consistent and less of a peak activity can be useful.
Some dogs have very variable gastric transit times day to day, making it harder to stabilise with an insulin that has a rapid acting peak activity designed to coincide with the post-prandial glucose spike.
Because beta-cell toxicity is a major factor in cats, oral hypoglycaemics have been used, although potential toxicity limited their effectiveness.
Recently, however, a sodium-glucose cotransporter-2 inhibitor, bexagliflozin, has been licensed for use in cats in the US. Limited peer review data have been published to date.
Hadd et al (2023), reporting on 81 newly diagnosed cats given once-daily dosing (15mg) for eight weeks, demonstrated reduction in hyperglycaemia in 68 cats associated with an improvement in neurologic status, musculature and hair coat quality, and owner assessment of quality of life.
At day 56, based on an eight-hour blood glucose curve, 43 out of 75 cats had an average blood glucose within reference interval (3.6mmol/L to 8.6mmol/L).
However, serious side effects (vomiting, diarrhoea, and dehydration) occurred in eight cats, leading to death or euthanasia in three cases associated with euglycaemic DKA.
In a small study of five unstable diabetic cats (Benedict et al, 2022) on insulin, significant falls in insulin requirement and average blood glucose were recorded when bexagliflozin was added to the management regime.
Client communication is key to successful management of diabetics.
Without good support and advice, owners will start looking elsewhere (Albuquerque et al, 2020), usually to online forums, many of which are not moderated and contain a lot of inappropriate, inaccurate and out-of-date advice. Given the prevalence of DM, most clinics will be managing multiple diabetic patients, making diabetic clinics, advice sheets and lead professionals within the practice a good proposition.
While it is important to try to deliver optimal management, including effective monitoring, dietary advice and lifestyle change, success is most often achieved through consistency of owner regime and tailoring monitoring to a level that the patient will tolerate – and the owner can afford. This means individual plans rather than trying to achieve “gold standard care”, which is unworkable for many clients and can result in worse outcomes than a more pragmatic approach. Part of delivering good, individualised care is understanding the criteria for success, which will vary between clients and may be fairly straight forward and easy to monitor (for example, no longer getting the owner up at night to go out to urinate, a reasonable thirst and stable bodyweight).
Other owners want and need more detailed information about the diabetic control, in which case flash glucose monitoring (Figure 1) may be a helpful tool, as it improves diabetic control and reduces owner anxiety, making it is easy for them to get an instantaneous glucose level.
For some owners, home blood glucose monitoring is the right approach, but the frequency of sampling/curving does need checking, as the carer can become rather obsessed, which can be damaging to both patient and their own quality of life, lead to frequent regime changes and, ultimately, poorer diabetic control.
Successful management centres on two factors:
Diabetic cases can be very hard to manage – particularly when clients are on a budget and want “perfect control” without letting the practice undertake appropriate investigation and monitoring.
Many of these cases will be with the practice for years, so having robust frameworks for communication and decision making will build owner confidence, and achieve better control.
Some diabetics are unstable and difficult to gain good control of, while others are very brittle, with slight changes causing large effects on glycaemic control. These do not necessarily represent failures in care, making it important that practice staff involved in looking after diabetic patients realise adequate control in some patients is impossible to achieve – if it was easy, there would not be half a million papers on the subject.
