What's new, what's old, and what works in diabetes mellitus (Proceedings)

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What's new, what's old, and what works in diabetes mellitus (Proceedings)

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Nov 01, 2010

Diabetes mellitus (DM) is one of the most common endocrinopathies seen in cats. DM arises from a variety of pathophysiological causes. Causes of DM in cats include islet-specific amyloid deposition, chronic pancreatitis, obesity, infection, other illness, drugs, etc. Obesity and islet-amyloidosis are potential causes for NIDDM. Both conditions cause insulin resistance. Severe amyloidosis will cause IDDM. In cats being treated with insulin, their needs may wax and wane. This may be due to "glucose toxicity". Animals that are persistently hyperglycemic will develop insulin resistance. As their hyperglycemia is corrected with insulin, their insulin resistance will dissipate, lowering their insulin needs.

Clinical Features

There are 4 classic signs of DM: Polyuria, Polydipsia, Polyphagia, and Weight loss. Due to the relative or absolute lack of insulin, the patient becomes hyperglycemic. When the renal threshold is exceeded, glucosuria with resultant polyuria develops. Without insulin, peripheral tissues are unable to utilize glucose. This leads to the break-down of muscle and fat. Basically, as far as the patient's body is concerned, it's starving & in a catabolic state. Additionally, polyphagia develops because the amount of glucose entering the satiety center in the hypothalamus is mediated by insulin. If glucose does not enter the satiety center, the patient constantly feels hungry.

Unfortunately some cats are not presented for veterinary care until the DM is progressed. Patients may be suffering from diabetic ketoacidosis or peripheral neuropathy at the initial visit.

Diagnostics

DM is diagnosed based upon clinical signs and documentation of fasting hyperglycemia and glucosuria. It can be somewhat challenging to diagnose DM in cats because of their frequent severe stress hyperglycemia. Fructosamine levels can be used to establish the diagnosis.

A minimum data base consisting of a CBC, chemistry profile, urinalysis plus culture should be obtained on all cats suspected of having diabetes. This is necessary to establish the diagnosis, rule out any concurrent disorders and evaluate the overall health of the patient.

CBC:

there are not any "classic" findings for DM on the CBC. Leukocytosis may suggest either inflammation or infection. Pancreatitis and infections are problems commonly seen with DM. Mild polycythemia suggests dehydration. Mild anemia typical of chronic disease may also be seen.

Chem panel: hyperglycemia will be present. Other changes that can be present:
     • Liver enzymes are often elevated due to either hepatic lipidosis or pancreatitis.
     • A mild prerenal azotemia may be found. It can be challenging to rule out kidney disease in diabetics because DM causes many alterations in the urine. It may be necessary to recheck bloodwork after fluid diuresis (prerenal azotemia will resolve with adequate hydration).
     • Hyperlipidemia and hypercholesterolemia will be found in diabetics. This is because 1)decreased movement of triglycerides into fat depots 2)decreased hepatic degradation of cholesterol and 3)increased hepatic production of very-low-density-lipoproteins. These lipid abnormalities cause of many of the vascular abnormalities found in people.
     • Amylase and lipase are poor indicators of pancreatitis. PLI may be measured to help diagnose pancreatitis. Abdominal ultrasound is useful for diagnosing pancreatitis.