The client is in tears. The cat is huddled in the corner, confused and sick. A family friend is sitting on the stool, trying to comfort the owner. It is a hard situation- the owner came to me with the impression that her excessively urinating cat needed antibiotics for his urinary tract infection and is now getting a lecture on diabetes mellitus.
So what happened? Apparently the kitty, named Josh, has been losing weight despite eating quite a bit. He drinks his water, but also drinks from the toilet. He likes to drink from the faucet. In fact, he loves water and appears to drink all the time, I discover as I ask more questions.
He recently started urinating in inappropriate places. True, his litter box has been getting full quicker than usual, but it really didn’t make an impression on the owner until the peeing on the rug started. Naturally, the owner went to the Internet and self-diagnosed a urinary tract infection and called for antibiotics over the phone. When I, the veterinarian, wouldn’t prescribe the ‘necessary’ antibiotics without an exam, the woman reluctantly scheduled an appointment but insisted her friend be present to make sure I didn’t pull any ‘funny stuff’.
A simple urine test confirmed what I suspected. The glucose was high, indicating diabetes. Now comes the lecture on diabetes mellitus.
In any elderly cat with increased urination and drinking, diabetes mellitus must be suspected. Other major possibilities include a urinary tract infection (which is often concurrent with diabetes mellitus), kidney disease and thyroid disease, although there are a plethora of other options which can be ruled in or out with various tests.
A urine test is a quick a decisive method to start deciphering the problem. In this case, the urine specific gravity was high, which reduced the possibility of kidney disease. The glucose was also high, which makes diabetes mellitus probable, but not necessarily correct.
After convincing her friend that we needed to investigate further, we proceeded to the next step. Blood tests must be taken to evaluate the metabolic status of the cat, including a liver screen, pancreas screen, kidney screen, white and red blood cell screen and a thyroid test. In this case, all was normal except the glucose, which was 403ug/dl. However, I advised the pair, who were now listening to my every word, I require one more test to be definitive. A fructosamine, similar to a glycosylated hemoglobin in humans, allows me to evaluate the overall average of blood sugar in the blood over a span of two weeks, thus determining if the glucose is high only today due to stress, or is chronically high, due to diabetes mellitus. With all the clinical problems, the other urine and blood tests and the abnormally high fructosamine result, I can be confident that Josh has diabetes mellitus.
So now what? 50% to 70% of diabetes in cats is insulin-dependent (Small Animal Internal Medicine, 2nd Edition), and is due to the pancreas not producing enough insulin for the body to absorb and utilize glucose, which is the energy source for cellular function. Like a key that opens a door, insulin opens cells for glucose to enter. Without a key, glucose wanders around in the blood with nowhere to go, hence the elevated levels of glucose in the blood stream. Unfortunately, the cells are desperate for the glucose, and cease functioning without it, kinda like a child trapped in a house with no food while a parade of yummy snacks parade around out front, just out of reach. Eventually, the child succumbs to starvation despite the fact that food is just outside. Yet, if a key arrives in the form of insulin, the door is unlocked and food floods into the house, saving the child.
The excess blood glucose causes an osmotic gradient to form (remember when you dosed off in biology class, thinking all that stuff was irrelevant?). This makes water from the body enter the blood stream to dilute the glucose, increasing the urine production of the body in an effort to release the excess water. Thus it results in more urine in general, which is where we started—a urinating kitty.
30% to 50% of diabetic cats are non-insulin dependent. Obesity, excess carbohydrate intake, islet sell amyloidosis, immune complexes and multi-factorial issues all play a role in this form of diabetes mellitus. In this form, it is not just the insulin (the key) that is missing, but also the door mechanism that the key must enter to unlock the door. This mechanism is called an insulin receptor. It is the lock on the door that must be opened by the insulin key. As these receptors decrease, doors to the cells become walls, and despite adequate glucose or insulin, the insulin cannot enter.
So which one does this cat have? Answer, I don’t know. Insulin requirements in cats change. Some cats will only have transient diabetes due to another factor, and then once the other issue is resolved, revert to a non-diabetic state. Others require constant and life-long insulin. In fact, both are common, and in my experience, are often intermixed.
Virtually every veterinarian will start this kitty on insulin. Oral diabetic medications are notoriously unhelpful in cats. Most veterinarians will recommend a diet change to a prescription diabetic friendly food.
Here is where I diverge from the ‘norm’ and advise a more holistic, natural path. Stay tuned to next week’s blog and we will delve into the treatment options for diabetes mellitus in cats.