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.

What do the kidneys do?

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.

What happens when feline kidneys don’t function normally?

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.

How and why does the cat get sick?

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.

How is chronic kidney disease diagnosed?

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.

How is chronic kidney disease treated in cats?

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.

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.

 

General

Vomiting is one of the most common symptoms in cats. A common symptom means that vomiting is a symptom of the entire body, and therefore there may be a number of different causes in the background. Sometimes it can be difficult for the owner to distinguish between coughing and vomiting. Indeed, coughing suggestive of respiratory disease can be misinterpreted as, for example, vomiting or trying to clear the throat from hair. Vomiting is defined as a reflex series in which the pumping motion of the abdominal muscles and diaphragm causes the contents of the stomach to be emptied by pressure. During coughing, on the other hand, the cat often stretches its neck long and "pushes" air or mucus out of the airways without pumping movement from the stomach or emptying the stomach contents into the mouth. It is also normal for cats to empty their stomach by vomiting due to undigested material such as feathers and bones of prey animals. In this case, the cat may aid in the vomiting reflex by eating grass, for example. But how do you know when vomiting is worrying?

Cats groom their fur

All cat owners are familiar with the fact that cats groom their fur daily by licking and plucking it. In this case, it is normal that small amounts of hair end up in the stomach and intestines. In a balanced situation, the hair passes through with the stool, and only rarely does a cat have to vomit and empty the stomach of hairballs or suffer from constipation due to hair. The balance may be shaken if abnormal amounts of hair start to move into the intestine or because of a problem with the digestive tract and the hair does not pass through the intestine normally. Especially in long-haired cats, the amount of hair entering the intestine at the time of hair loss can increase significantly. Also certain hair types may result in continuously increasing amounts of hair entering the intestine. Skin problems or excessive grooming due to pain or behavioral disorders, may also increase the amount of hair entering the gut. It is therefore always important to consider whether there is a predisposing cause for hair vomiting that could be addressed and treated, rather than just treating the hairball vomiting symptomatically. However, if persistent episodes of excessive hair loss, vomiting, or constipation have not been shown to have a clear predisposing cause, or if the cause cannot be remedied, measures preventing the hair from accumulating in the cat's stomach and intestines should be taken. Increased drinking can promote normal hair passage through the digestive tract; for example, the cat may be offered tuna or honey flavored water, or the number of water bowls can be increased by placing them around the apartment if the cat likes to drink in unusual places. To improve bowel function, a high fibre diet is recommended. Choose high fibre food or introduce fibre supplements. Cat malt, paraffin oil or lactulose can be used for short periods or as a treatment when needed, as in continuous use they may interfere with normal gut function and food absorption. Regular grooming and finishing by wiping with eg. a damp cloth is recommended to remove small loose hairs from the fur, otherwise they may end up in the cat’s mouth.

Typical causes for symptoms

Nausea, loss of appetite and vomiting can be caused by a variety of reasons that may not involve hairballs at all. Food allergy, inappropriate food or contaminated food can trigger symptoms. Many medicines, unsuitable plants or intake of other substances known to be toxic or harmful can also cause symptoms. The digestive tract may also have an internal parasitic infection, chronic inflammation, foreign objects or a tumor. Foreign objects, such as pieces of a plastic bag or soft parts from a toy, are likely to cause only temporary vomiting, but eating a cord or eating an ear plug can cause intestinal obstruction, which can have very serious consequences. Also many visceral diseases such as diabetes, hyperthyroidism, kidney, liver, biliary or pancreatic problems commonly lead to nausea, fasting and vomiting.  Only on rare occasions do dental diseases cause vomiting or loss of appetite in cats, even though a food dropping, drooling cat that has abandoned kibbles and switched to wet food alone, may seem to have something wrong in the mouth. In such cases the behaviour is commonly due to nausea, and the fact that wet food does not cause uncomfort and nausea in the same extent as dry food.

Cat's age, lifestyle and history

The age, lifestyle and history of your cat will help determine what causes may be more likely than others. For example internal infections, inappropriate food, foreign objects, and consumption of inappropriate matters are likely causes of symptoms in young cats. A young cat from a large cattery may have symptoms due to a parasitic infection, or may carry asymptomatic giardia, which may infect older cats in the family. An outdoor cat, and especially a predatory cat, is also more susceptible to internal infections or intoxication. An indoor cat that has lived alone or in the same herd for a long time without newcomers is highly unlikely to have an internal parasitic infection. In older cats, symptoms caused by endocrine disorders and tumors are much more common.

Duration and severity of symptoms

Symptoms can be acute, ie. lasting less than a week, or chronic with symptoms for weeks, months, or even years. The severity of the symptoms can range from a mild to a very serious collapse in the general condition, where the cat does not eat, is dehydrated, in pain and even feverish. Acute and rapidly transient symptoms of vomiting in an alert and pain free cat does not require immediate examination or treatment, but if eating does not return to normal within a few days, the vomiting is abrupt and the cat cannot hold his food, is in pain or very weak, it is good to seek medical advice immediately.  Most commonly, chronic wavy symptoms such as gradually creeping vomiting, on / off loss of appetite, and weight loss occur in chronic endocrine disorder, where examination and treatment is not acute. However, even in these cases, it is a good idea to consult a veterinarian in a timely manner, which often makes it much easier to treat the underlying cause or get it under control. Acute syndromes causing acute symptoms, on the other hand, are often severe and require immediate medical attention and treatment.

Examination and treament

Reviewing the cat's history with the owner, reviewing the severity and duration of the symptoms, and a thorough veterinary examination are the most important steps for choosing the correct follow-up exam. Unnecessary tests are also avoided.  In acute cases with mild symptoms, dietary changes or symptomatic treatment may be recommended without an examination, as the underlying cause for symptoms is likely to be self-healing. Acute severe and chronic symptoms often require blood tests. Occasionally, urine and/or fecal samples are also advisable. For example, X-rays can assess the size and shape of organs and the possibility of a foreign object. Often a well-performed ultrasound examination is more informative for a vomiting cat than an X-ray. This enables an examination of the structure and shape of the internal organs, indicates the possibility of a tumor or degeneration in tissues, and show the thickness, structure and contents of the mucous membrane of the stomach and intestines, as well as possible obstructions and inflammation in the pancreas and bile ducts, bladder contents, or whether there may be free fluid in the abdomen or reactive lymph nodes. The aim is to combine the various exam results to find the cause of the symptoms and then discuss treatment options and prognosis with the owner.

 

The article was originally published in Finnish Siberian Cats Association, issue 1/2019.

Lähteet:

Andrea Harvey & Séverine Tasker. BSAVA Manual of Feline Practice A Foundation Manual. BSAVA 2014.

Jacquie Rand. Problem-based Feline Medicine. 1.p. Saunders, Toronto 2006.

Susan E. Little. August’s Consultations in Feline Internal Medicine vol 7. Elsevier 2016.

Etienne Côté. Clinical Veterinary Advisor Dogs and Cats. 3 ed. Elsevier, Missouri 2015