Diabetes is an endocrine disorder in which the pancreas doesn't make enough (or any) insulin due to the destruction of the pancreatic beta cells (type 1 diabetes) or the cells within the body fail to respond to insulin, known as insulin resistance (type 2 diabetes). When this happens, glucose builds up in the blood but the cells are starved of glucose required for energy.
Most of the complications are related to uncontrolled diabetes, which highlights the importance of diligent control as well as regular monitoring and a close relationship with your veterinarian who will need to closely monitor the diabetic cat.
When hyperglycemia (high blood glucose) occurs, the body breaks down fat as an alternate fuel source. Fat is the back up fuel option, however when the liver metabolises fat, waste products known as ketones are released which causes the blood to become too acidic (known as metabolic acidosis). The body tries to get rid of ketones by increasing urination, which leads to dehydration. Blood glucose levels remain high.
- Missed meal
- Missed insulin administration
- Insufficient insulin
- Concurrent illness (pancreatitis, hepatic lipidosis)
- Recent surgery
- Increased thirst
- Increased urination
- Increased or decreased appetite
- Intravenous fluids to treat dehydration
- Administration of insulin
- Treating the underlying cause if there is one.
Diabetic nephropathy (diabetic kidney disease)
A type of chronic and progressive kidney disease caused by high blood glucose levels which damage the tiny filtering structures (glomeruli) in the kidneys.
It is the role of the kidneys to clean the blood, removing waste products via the urine while re-capturing important substances. Long-standing high glucose in the blood of diabetic cats as well as high blood pressure which is also associated with the condition cause damage to these filters. As the filtering units become damaged, important proteins, in particular, albumin are lost via the urine.
- High blood pressure increases the pressure within the capillaries, which increases the filtration rate within the glomerulus.
- Vasoconstriction of the efferent arteriole occurs in response to renin (a hormone secreted by the kidney when there is a drop in fluid volume within the body) in order to maintain blood pressure and volume status. This too causes an increase in the filtration rate. The exact physiology still isn't fully understood, but it is believed that hyperglycemia directly affects the intra-renal renin-angiotensin-aldosterone system which leads to efferent vasoconstriction. As the pressure within the kidney increases, the mesangium (a structure within the glomerulus which supports the capillaries) expands, inflammation occurs, which causes damage to the filtration system which becomes leaky.
Early diabetic nephropathy may produce no symptoms at all, it is only when a significant amount of damage has occurred that symptoms may present. These are associated with kidney failure and may include:
- Increased thirst
- Increased urination
- Nausea or vomiting
- Weight loss
- Anorexia (loss of appetite)
- Albumin in the urine
- High blood pressure
Ensuring that blood sugar levels remain within normal range with regular meals, insulin administration and careful monitoring of blood glucose levels. Phosphorous levels can build up in the blood of cats with kidney disease as the kidneys become less effective in filtering the blood.
- As well as diabetic control, treatment is the same as that of kidney disease and may include:
- Managing high blood pressure with medication if necessary.
- A high-quality diet which is reduced in protein and phosphorous.
- Phosphorus binders can help reduce absorption of phosphorus from the diet.
- Ensuring adequate water intake and treating dehydration with intravenous fluids where necessary.
- Erythropoietin is a hormone produced by the kidneys which stimulate red blood cell production in the bone marrows. Failing kidneys often have a low red blood cell count due to lower levels of this hormone. The only form available is the human form, this may be prescribed if your cat has become anemic.
A common complication caused by persistent hyperglycemia, neuropathy is a type of nerve damage which occurs as a result of prolonged levels of high blood glucose. In cats, the nerves in the hindquarters are most often affected (peripheral neuropathy), however, it can also affect the stomach (gastroparesis).
There are a number of factors which contribute to the development of neuropathy, which aren't fully understood yet. It is believed, in part due to a cascade of events including narrowing of the blood vessels, proteins and lipids becoming glycated (advanced glycation end products) and excessive release of cytokines (a group of proteins produced by the immune system which act as chemical messengers).
Hind legs: The most common symptom of diabetic neuropathy is a progressive weakness in the hind legs. Affected cats will have difficulty jumping and develop a plantigrade stance, meaning instead of walking on their toes, as they normally do, they walk on their hocks.
If caught early, diabetic neuropathy can be reversed. Treatment is aimed at correcting hyperglycemia with proper diabetic treatment, following dietary guidelines, Methylcobalamin (vitamin B-12) supplements and close monitoring of your cat's glucose levels.
This is a serious and life-threatening condition in which the level of glucose in the blood falls dangerously low. When this occurs, the cells are starved of glucose, necessary for energy. The brain is most at risk as the brain relies on glucose alone for energy, while other cells can use alternate forms (protein or fat) when glucose levels drop.
Poorly regulated or newly diagnosed diabetes are the causes of hypoglycemia, these may include:
- Improper glucose administration (too much insulin)
- Missed meals
- Certain medications
There are several other causes not related to diabetes including:
- Addison's disease
- Insulin-secreting pancreatic tumour
- Glycogen storage disease
- Liver disease
- Sepsis (bacterial infection of the blood)
Most of the symptoms of hypoglycemia relate to neurological dysfunction, symptoms vary depending on the severity of the condition but may include:
- Increased appetite (polyphagia)
- Ataxia (wobbly gait)
- Heart palpitations
- Poor coordination
- Hypoglycemia is a medical emergency and any hypoglycemic cat should be seen by a veterinarian.
- If your cat is still conscious and able to swallow, rub some corn syrup, honey or maple syrup onto his gums and then take him directly to his veterinarian.
- If he is unconscious, take him to the veterinarian and administer glucose as outlined above along the way.
- Your veterinarian will check his sugar levels and administer intravenous dextrose if necessary.
- Glucocorticoids such as prednisone may also be given to help stabilise blood sugar levels.
- Regular monitoring of your cat's blood glucose levels will be necessary until they become regulated.
Less common in cats than dogs, cataracts are a clouding of the lens within the eye which results in impaired vision. There are many possible factors which can lead to cataracts including diabetes. Either part of or the entire lens can be affected and they may develop in one or both eyes.
The lens receives its nutrients from the aqueous humour, in the cat with diabetes, high blood sugar leads to high glucose levels in the aqueous humour also, from there it enters the lens where it is converted to sorbitol (which is a form of modified glucose). Sorbitol can affect cells and proteins in the lens, as well as that, high levels of sorbitol in the lens which can not be used causes the lens to become hypertonic, and water is drawn into the lens causing it to swell.
- Blue/grey cloudy spots in the eyes
- Poor vision, such as bumping into objects, reluctance to jump
Surgery involves removal of the lens. Ultrasonic waves are used to liquefy the lens, which is then aspirated (sucked out). This treatment is known as "phacoemulsification". In some (not all) cases, an artificial lens will then be inserted. This is the most common method of removal.
Another method is extracapsular lens extraction, which involves removing the lens as a whole. This is indicated where the necessary equipment for phacoemulsification isn't available or if the lens is too solid to be broken up.
Urinary tract infections
Any cat can develop a urinary tract infections, but diabetic cats are at an increased risk.
Higher levels of glucose and protein in the urine as well as a compromised immune system in the diabetic cat can make a favourable environment for bacterial growth within the urinary tract.
- Frequent trips to the litter tray
- Urinating outside the litter tray
- Crying when going to the toilet
- Blood in the urine
- Oral antibiotics will be prescribed to treat a urinary tract infection.
- Ensuring your cat's glucose levels remain stable.
Unregulated diabetic cats are at risk of weight loss due to lack of glucose.
When glucose is not able to move into the cells from the blood, the body switches to an alternate fuel supply to provide the cells with energy. This comes from your cat's fat reserves.
Obviously, weight loss is the main symptom. It is often quite hard to determine if your cat has lost weight by appearance alone. The diabetic cat should be weighed regularly to ensure his weight remains stable.
Ensure your cat's glucose levels remain stable with daily monitoring.
Following on from weight loss, if the cat's body starts to use fat stores for fuel, hepatic lipidosis can develop. This is a life threatening condition which needs immediate and aggressive treatment. Up to 70% of cats who are treated immediately can recover from hepatic lipidosis, untreated the outcome is grave.
When the body begins to use an alternate source of energy due to glucose being unable to enter the cells, fat is sent to the liver for processing. However, the liver is not very efficient at metabolising fat and as it begins to accumulate, the liver cells become overwhelmed and unable to function properly.
- Loss of appetite
- Weight loss
- Muscle wasting
- Drooling (due to nausea)
- Jaundice (yellow gums)
- Poor coat condition
Intensive nutritional support with a high-calorie food fed several times a day. If your cat is not eating, he will need to have a feeding tube inserted.
Supportive care may include medications to control nausea and vomiting and intravenous fluids to treat dehydration.
Once again, proper insulin administration and regular monitoring of your cat's blood glucose levels and the urine for ketones and his weight are essential.
If you do notice your cat losing weight, or if he loses his appetite, see your veterinarian immediately.