Author: Veterinarian Mimma Aromaa
I work as a veterinarian at Kaarinan Eläinlääkäriasema Oy (Kaarina, Finland). In particular, I am interested in the internal diseases of cats and dogs, ie. vomiting, diarrhoea, and weight loss - sluggish and tired patients are a daily challenge for me. I specialize in extensive abdominal ultrasound examinations. My two Burmese cats are my daily guide to the interesting soul landscape of cats.
The main function of the kidneys is to filter metabolic waste products from the blood. The kidneys also regulate the body’s fluid balance, acid-base balance and electrolyte balance. In addition, the kidneys take part in the regulation of blood pressure and red blood cell synthesis. The capacity of the kidneys to maintain normal functions is very high. This means that signs of renal insufficiency, or poor function of the kidneys, are seen only when over 70 % of kidney function is lost. Feline kidneys are capable of retaining water very efficiently due to the domestic cat’s ancestors having accustomed to very dry desert conditions. Thus, scarce drinking of normal symptomless cats is not alarming and urine produced by cats is very strong.
A cat with renal insufficiency can no longer retain water as efficiently or produce very concentrated urine typical to the species. This results in thirst, which leads to increased drinking and urinating so that the metabolic waste products are eliminated. Dehydration of the body can also cause constipation. However, increased drinking and urinating might not be the most distinct or first sign of renal insufficiency in a cat. Healthy cats that eat mainly dry kibble drink more than those eating wet or raw food. Some cats are prone to playing with water, and drinking from odd places such as the sink is normal. This means that quantifying limits for abnormal drinking is difficult and it’s important to note changes in your cat’s drinking habits. Is the cat seen drinking more than usual? Are the urine clumps in the litter box bigger than before? Is the change momentary or persistent and not explained by eg. a change in the cat’s diet?
Changes in blood values are seen when metabolic waste products accumulate in the body. Kidney values measured from blood are actually waste products of normal metabolism. The most frequently measured kidney value is creatinine, which is a breakdown product of muscle metabolism. Another common kidney value is urea (blood urea nitrogen or BUN), which is a waste product of protein metabolism. A rise in these values is indicative of impaired renal filtration. Especially the accumulation of urea leads to nausea and anorexia (a sustained loss of appetite) in the cat.
Changes in especially calcium, phosphorus and potassium are seen when the ability of the kidneys to control electrolyte balance fails. The changes in the balance between calcium and phosphorus lead to weakening of bones. Low potassium can be the cause of lethargy and weakness.
High blood pressure and anemia are common findings in the cat with chronic kidney disease, as the kidneys participate also in the regulation of blood pressure and red blood cell production. Chronic illness and poor appetite cause cachexia, or wasting syndrome, which is seen as a decline in body weight and a dry and brittle fur coat.
The most common reason for chronic kidney disease is idiopathic degeneration of the kidneys, which means that the reason for the degeneration is unknown. This disease progresses slowly and the changes are irreversible. Signs of idiopathic kidney degeneration are usually seen in aging cats over 7 years of age. It may be hereditary and is more common in certain breeds. There are also reasons that can lead to damage of kidney tissue in a cat of any age and thus lead to chronic kidney disease. For example, infections in the kidneys or elsewhere in the urinary tract, urinary obstructions, toxins (eg. certain drugs and poisonous plants), tumors, viral diseases such as FIV and FIP and disruptions of renal blood flow can have an effect on kidney function. Some of the aforementioned reasons may at first cause an acute renal injury, which might be reversible if treated efficiently and early on. In degenerative chronic kidney disease the progression of the disease is usually more straightforward. Determining prognosis and progression of the disease may be difficult in chronic kidney disease caused by other factors. In addition, the progression of the degenerative process may quicken or renal insufficiency worsen momentarily due to infections, medications or other chronic illnesses.
It is not always clear if the reason for chronic kidney disease is degeneration or another cause of renal insufficiency. Thorough patient history, signs and symptoms, blood and urine values and other examinations such as ultrasound examination of the kidneys and urinary tract and blood pressure measurement are key when assessing the situation. Kidney biopsies could clarify the situation and prognosis. However, the treatment of chronic kidney disease in cats does not differ much depending on the background factors, so renal biopsies are not routinely taken. The progression of the disease is monitored by keeping a close eye on the condition of the cat and taking blood and urine samples. Kidney values might be momentarily high due to eg. infections, obstructions, medications, dehydration and other factors. Continuously high kidney values or continuous indication of kidney disease in the urine are indicative of chronic kidney failure and the diagnosis cannot be definitively made from just one sample. All other possible reasons for renal insufficiency or the worsening of chronic kidney disease have to be ruled out and treated. When the cat’s condition is stable, staging of chronic kidney disease may be done by controlling blood and urine samples and measuring blood pressure.
The overall situation of the cat needs to be taken into account when interpreting kidney values. We cannot be sure two different cats are in the same stage of chronic kidney disease just by comparing their kidney values. The stage of chronic kidney disease is very different in a cachexic cat with moderate signs, a cat with a healthy weight and slight signs and a cat with a healthy weight and severe signs. The kidney values of the thin cat lacking muscle with moderate signs are probably falsely low due to low muscle mass. The prognosis for this cat is worse than for the cat with a healthy weight and slight signs. On the other hand, the acutely symptomatic cat with a healthy weight probably has acute renal failure, which has to be treated intensively in-hospital to support returning to normal kidney function. After this cat’s condition has stabilized, blood values need to be controlled to check for development of chronic kidney disease.
There is no cure for chronic kidney disease in cats. Life expectancy can be increased with proper diet, dietary supplements and supportive treatment. The cat needs enough water, treatment of possible constipation and it needs to be able to urinate often enough. Keeping a healthy weight is attempted with tasty food and treating nausea with medications if needed.
Control visits are planned individually with the cat’s condition, the owner’s options and the progression speed of the disease in mind. The disease is usually controlled every 3-12 months depending on these variables. A thorough physical examination, blood and urine samples, blood pressure and ultrasound examination are controlled on a case-by-case basis. The diet required for the particular stage of the disease is decided based on these results. The need for dietary supplements for balancing potassium and phosphorus, blood pressure medication and anti-nausea medication is assessed. Other co-occurring illnesses and infections need to be treated.
DVM Iida Niinikoski
Diabetes mellitus is a fairly common disease in the modern day domestic cat. Out of 200 cats, approximately 1-2 develop diabetes during their lifetime. In diabetes mellitus the blood glucose level of the cat is constantly too high. Feline diabetes is similar to type II diabetes mellitus in humans. The corner stones of treatment of diabetes are effective insulin treatment early on in the disease, diet and avoidance of obesity. With aggressive treatment early on combined with efficient monitoring, some cats go into remission and can be managed without insulin later on.
Insulin is a hormone secreted by the beta cells of the pancreas. It increases the movement of glucose in the blood into cells of the body, which in turn decreases the amount of glucose in the blood. Insulin resistance occurs often early on in the disease: insulin is secreted by the pancreas, but it does not function properly in the body. This means that blood glucose levels remain high. Obesity, certain diseases (e.g. acromegaly and inflammatory conditions) as well as some medications (e.g. cortisone) are known to cause insulin resistance.
Due to insulin resistance blood glucose level is high, which leads the pancreatic beta cells to secrete even more insulin. If insulin resistance continues, the beta cells tire, and the production of insulin decreases or completely stops. Insulin production might normalize early on in the disease process if the factors causing insulin resistance are gotten under control. Lifelong treatment with insulin is needed if the destruction of pancreatic beta cells is complete. The avoidance of obesity is key to preventing diabetes. A diet high in protein and low in carbohydrates improves glucose balance and reduces insulin resistance.
Multiple risk factors besides obesity have been identified. These include increasing age, male gender and physical inactivity. Some breeds such as the Burmese cat are more at risk for development of diabetes. The typical diabetic patient is an overweight 11-13-year-old male cat who lives indoors.
Typical signs of diabetes are excessive drinking and urinating. The cat loses weight despite having a good appetite. The signs progress slowly, and it is often difficult to say exactly when they started. If left untreated, the disease leads to diabetic ketoacidosis, in which vomiting and extreme fatigue occur. Diabetic ketoacidosis is a life-threatening condition.
If diabetes is suspected a blood and urine sample are taken at the vet. The diagnosis is based on clinical signs combined with the laboratory results. Blood glucose in cats is affected by stress (caused by a visit to the vet for example), so just a slightly high blood glucose value does not necessarily mean the cat is diabetic. A high fructosamine value supports the diagnosis of diabetes, as it describes blood glucose levels from the past few weeks.
The goal of treatment is to keep blood glucose at a level where the signs of diabetes are nonexistent and the quality of life of the cat is good. Drinking and urinating are not excessive, and the cat is bright and alert. Too high and too low blood glucose levels are avoided. The primary goal in recently diagnosed diabetic cats should be remission, in which insulin is no longer needed after the initial treatment period. This often requires tight monitoring of blood glucose levels.
The management of diabetes requires a lot of commitment from the owner. Diabetes is treated by subcutaneous injections of insulin. Usually the cats tolerate the injections well, but repetitive injections combined with tight monitoring might cause stress. The type and dosage of insulin is determined by the treating veterinarian. Oral diabetes medications are often ineffective and are not considered a first-line treatment.
Home monitoring of blood glucose levels is an important part of the treatment, especially if aiming for remission. Portable blood glucose meters are easy to use. Blood glucose curves can be done to see how low the blood glucose level drops after injection of insulin and how long the effect of the injection lasts. In some cases urine dipstick tests can be used for detection of glucose in the urine, but this is not a reliable method of monitoring blood glucose levels on its own.
A diet with high protein and low carbohydrate helps keep blood glucose levels stable. Commercial diets for diabetic cats are available. Feeding of canned food instead of dry food is recommended because of the lower caloric density and ease of portion control.
The weight of the cat is monitored at home: obesity is avoided but fast weight loss might be indicative of poor control of the disease. Intentional weight loss needs to be slow and gradual. Moderate exercise is beneficial and improves weight control and general well-being. Playing and climbing should be encouraged. Changes in appetite, drinking and urinating need to be noted. When blood glucose levels are too high, the excess glucose is excreted in urine. Glucose pulls out a lot of water with it, which increases the amount of urine and thus the amount of water the cat needs to drink.
Visits to the veterinarian are frequent especially in the beginning of management of the diabetic cat. Blood glucose and fructosamine levels are monitored. Diabetes predisposes the cat to developing urinary tract infections and urine samples are controlled. Blood tests are checked for signs of other issues, because blood glucose balance is strongly affected by different inflammatory conditions as well as other diseases. Dental care is very important. If the disease is gotten well under control the frequency of veterinary visits can be decreased.
Hypoglycemia, low blood glucose, may occur rapidly and be life-threatening. Hypoglycemia may be due to an overdose of insulin due to insulin administration issues or if the pancreas has started secreting insulin and the cat is going into remission. Administration of insulin if the cat is not eating or is vomiting may also lead to hypoglycemia. Chronic hypoglycemia occurs when insulin is administered subcutaneously even though the pancreas has recovered and the production of insulin has begun. Hypoglycemia does not provoke hunger in cats, so the situation is not corrected by the cat eating on its own. The importance of blood glucose monitoring cannot be stressed enough.
Signs of hypoglycemia in cats may be very vague and variable and range from lethargy, ataxia and tremors to coma. Rapid treatment is required. If the clinical signs are mild, feeding a meal or sugar water/honey is suggested. In more severe cases, honey can be applied to mucous membranes of the cat before transportation to the veterinarian. Severe hypoglycemia requires treatment in-hospital with parenteral glucose.
Complications from hyperglycemia, high blood glucose, develop slower than those associated with hypoglycemia. Hyperglycemia occurs when there is a problem with the injection of insulin, the insulin does not function properly, the insulin dosage is not sufficient or something interferes with insulin function in the body. Diabetic ketoacidosis develops when blood glucose levels have been high for some time and the body starts to use free fatty acids for energy. This results in ketones accumulating in the body. Signs of diabetic ketoacidosis include vomiting, anorexia, excessive drinking and urinating, fatigue and sweet-smelling breath. The condition requires aggressive treatment in-hospital.
Neurological deficits may also be seen with chronic hyperglycemia. The most typical is plantigrade stance, in which the cat walks on the sole of the hindfeet and its heels touch the ground. Muscle atrophy in the hind limbs and difficulty jumping/climbing may be seen before plantigrade stance occurs.
The prognosis of diabetes is better if treatment is started early on. Cats are masters of hiding their illness, and routine veterinary visits and blood samples help with early detection of diabetes and other diseases. Prevention of obesity is essential in the prevention of diabetes and musculoskeletal diseases among others.
Diabetes is a severe disease and its treatment requires a lot of commitment from the owner. With proper management, diabetic cats can live many years of high quality cat life.