Toxins: Lilies or Antifreeze

Perinephric Pseudocysts

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Risk factors associated with the development of chronic kidney disease in cats evaluated at primary care veterinary hospitals (2014) Greene JP, Lefebvre SL, Wang M, Yang M, Lund EM & Polzin DJ Journal of the American Veterinary Medical Association 244 pp320–327 found that "Risk factors for CKD in cats included thin body condition, prior periodontal disease or cystitis, anesthesia or documented dehydration in the preceding year, being a neutered male (vs spayed female), and living anywhere in the United States other than the northeast."

Risk factors for development of chronic kidney disease in cats (2016) Finch NC, Syme HM & Elliott J Journal of Veterinary Internal Medicine 30(2) pp602-10 concludes "Results of our study suggest there is no single risk factor, exposure, or predictor that can explain development of CKD in cats and therefore cumulative effects of multiple risk factors and interactive factors should be considered. Cumulative exposure to risk factors in certain possibly genetically predisposed cats may contribute to a decrease in renal function."

Management and treatment of chronic kidney disease in cats (2016) Caney S In Practice Oct 2016 pp10-13 states "CKD is the end result of a wide range of primary disorders that cause irreversible damage to nephrons, eventually leading to reduced glomerular filtration rate (GFR). In a minority of cases a specific underlying cause can be identified, for example, neoplasia, polycystic kidney disease, renal amyloidosis, hypercalcaemic nephropathy. However, in the majority of cases no primary cause can be identified; in these cases tubulointerstitial nephritis and fibrosis are the most common histological changes, likely to be the end result of a degenerative process initiated by factors including, but not limited to, repeated episodes of renal tissue hypoxia, exposure to toxins, glomerulonephritis, pyelonephritis and repeated transient ureteral obstruction due to ureterolithiasis." She also says "In the majority of elderly cats with CKD the primary cause of the problem cannot be identified. However, in selected cases further investigation may identify the underlying cause of CKD, which may be helpful to owners and in some cases may open avenues of treatment to address the primary problem. In general, seeking a primary cause is more likely to be rewarding in younger cats and in cats with enlargement of one or both kidneys."

Renal diseases in cats (2015) DiBartola SP Presentation to Idexx Finland Congress discusses the various causes of CKD.

Hereditary/Congenital Abnormalities

Polycystic Kidney Disease (PKD)

Polycystic Kidney Disease, or PKD, is a condition in which cysts form on the kidneys. One of my Persians had PKD. There is detailed information about PKD on the Polycystic Kidney Disease page.

Renal Dysplasia and Renal Hypoplasia

In these conditions, there is a problem with kidney development:

• renal dysplasia: the kidneys do not develop normally

• renal hypoplasia: the kidneys do not develop completely

• renal aplasia: the cat has only one kidney

Renal aplasia is a form of renal hypoplasia. Cats with only one kidney tend to be male, and for some reason it is usually the right kidney which is missing. Renal anomalies (2016) Fitzgerald SE The Merck Veterinary Manual says that it is always accompanied by a lack of the tube that connects the kidney to the bladder (the ureter).

Amyloidosis

Amyloid is a type of protein found in the body. In amyloidosis, amyloid is deposited in organs and tissues where it does not belong, causing inflammation and damage. In cats, the deposits are often found in the kidneys, and they eventually lead to CKD.

Amyloidosis is not particularly common, but familial amyloidosis may be found in Abyssinian cats in particular, while Siamese and Oriental cats may also have hepatic amyloidosis. Changes in serum and urine SAA concentrations and qualitative and quantitative proteinuria in Abyssinian cats with Familial Amyloidosis: A five-year longitudinal study (2009-2014) (2015) Paltrinieri S1, Sironi G, Giori L, Faverzani S & Longeri M Journal of Veterinary Internal Medicine 29(2) pp505-12 says "The disease course of FA is variable in the conditions of appearance, severity and progression. The deposition of amyloid may deposit within one year and cause kidney disease or slowly and kidney function may stay relatively stable for years."

Cats with amyloidosis often have proteinuria.

International Cat Care discusses amyloidosis.

Overview of amyloidoses (2016) Tizard I The Merck Veterinary Manual

Strategies for protein losing nephropathy (2001) is a presentation by Dr MS Wallace to the Atlantic Coast Veterinary Conference in which she discusses glomerulonephritis and amyloidosis.

Lyons Feline Genetics Laboratory at the University of Missouri reports on a research project in the USA and Europe where you can provide blood or buccal samples from Siamese and Oriental cats to assist with research into feline amyloidosis.

Infections

Pyelonephritis

Pyelonephritis is inflammation of the kidneys which is usually caused by a bacterial infection. In many cases this will have started as a lower urinary tract infection which has risen into the kidneys.

 If your cat has a kidney infection and also has high bloodwork values, the bloodwork may improve once the infection is under control.

There is more information about pyelonephritis on the Pyelonephritis and Urinary Tract Infections page.

FIP (Feline Infectious Peritonitis)

Feline infectious peritonitis is a virtually always fatal illness that develops in a small number of cats who catch a type of virus known as the corona virus.

FIP occurs in two forms, effusive (wet) and non-effusive (dry). The wet form is generally considered harder to treat, but both forms can be fatal. It commonly affects kittens, but mature cats are more at risk too.

FIP is notoriously difficult to diagnose, and testing positive for the corona virus does not inevitably mean that the cat will develop FIP (the majority of cats test positive for the corona virus but never develop FIP).

Possible signs in bloodwork include elevated neutrophils and elevated total protein. You will usually see a low albumin:globulin ratio combined with very high globulin levels. An A:G ratio below 0.4 combined with elevated globulins, indicates that FIP is quite likely, assuming other causes of a low A:G have been ruled out, whereas an A:G ratio over 0.8 rules out FIP.

Symptoms of FIP include a raised temperature on more than one occasion and poor growth in kittens (an affected kitten is often much smaller than his/her littermates). Cats with the wet form of FIP often have ascites (fluid build up in the abdomen). Cats with the dry form may develop other symptoms, depending upon the area affected in the body. Commonly affected areas are the eyes, brain, abdomen and kidneys. Cats whose kidneys are affected may develop enlarged kidneys and CKD.

Very few cats on Tanya's Feline CKD Support Group have FIP, but I've had three CKD cats and one PKD cat, and fate decided I needed to experience FIP too. I lost the most adorable kitten in the world to dry FIP. You think CKD is bad? Well, FIP is worse, because there is so little you can do for it and so little hope, though there are some encouraging signs for treatments that may work in the future, such as GC376, though this is not yet commercially available. 

Cat Virus is the website of Dr Addie, a lecturer in veterinary virology and an expert on FIP. Her site is available in a number of different languages.

Cornell University College of Veterinary Medicine has a good overview.

The Winn Feline Foundation has information about FIP.

Newman Veterinary has information on FIP.

Feline Morbillivirus (FeMV)

Researchers have found that a recently discovered virus may also be present in some cases of interstitial nephritis in cats. To date the virus has been found in Asia, Europe and the USA. Feline morbillivirus, a previously undescribed paramyxovirus associated with tubulointerstitial nephritis in domestic cats (2012) Woo PC, Lau SK, Wong BH, Fan RY, Wong AY, Zhang AJ, Wu Y, Choi GK, Li KS, Hui J, Wang M, Zheng BJ, Chan KH & Yuen KY Proceedings of the  National Academy of Sciences of the United States of America 109(14) pp5435-40 discusses the initial findings. Yahoo! News reports on this study.

Epidemiological and pathological study of feline morbillivirus infection in domestic cats in Japan (2016) Park ES, Suzuki M, Kimura M, Mizutani H, Saito R, Kubota N, Hasuike Y, Okajima J, Kasai H, Sato Y, Nakajima N, Maruyama K, Imaoka K & Morikawa S  BMC Veterinary Research 12(1) p228 looked at tissue samples obtained at random from 100 deceased cats in Japan. It found that 29% of the cats had the morbillivirus or antibodies to it. However, the study could not find a correlation with CKD.

Chronic Infection of Domestic Cats with Feline Morbillivirus, United States (2016) Sharp CR, Nambulli S, Acciardo AS, Rennick LJ, Drexler JF, Rima BK, Williams T & Duprex WP Emerging Infectious Diseases 22(4) pp760-2 found the virus was also present in around 3% (ten cats) in the survey in the USA. Three of these ten cats had CKD. The strain appeared to be closely related to those in Asia.

Discovery of new feline paramyxoviruses in domestic cats with chronic kidney disease (2015) Sieg M, Heenemann K, Rückner A, Burgener I, Oechtering G & Vahlenkamp TW Virus Genes 51(2) pp294-297 found several new feline paramyxoviruses in urine samples from cats with CKD, whereas none were seen in the control group of cats. One of these viruses was similar to the form of feline morbillivirus found in Hong Kong and Japan. The researchers state that it is not yet known whether the virus is a potential cause of CKD or if the inflammation stemming from CKD merely enabled the virus to take hold.

Inflammation

Glomerulonephritis

The glomeruli are very fine blood vessels in the kidneys that act as filters of waste products to produce urine. When they become inflamed, it is known as glomerulonephritis.

Glomerular disease is an immune-mediated disease and is actually relatively rare in cats, though Feline hereditary and congenital kidney disease (2013) Suárez Rey M Veterinary Focus 23(3) pp17-25 states that there is a hereditary form that may be seen in Abyssinian cats. Otherwise it is usually secondary to some other condition such as an infection, inflammatory disease, dental disease, chronic pancreatitis, FIP , cancer or diabetes.

When glomerulonephritis occurs, proteinuria may result, so affected cats will often have low albumin levels. They may also have blood in the urine and occasionally a high urine specific gravity: Glomerular disease in small animals (2016) Brown SA Merck Veterinary Manual states "Although uncommon, urine specific gravity may be inappropriately high for the degree of renal dysfunction, a condition referred to as glomerulotubular imbalance."

The ideal treatment is to find and treat the cause of the inflammatory process. Using medications to suppress the immune system may help, though in some cases this may make things worse. Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine discusses glomerulonephritis and has a table (Table 1) showing possible causes and discusses the pros and cons of using immunosuppressants.

If the cause cannot be found, then the goal is to control the proteinuria as much as possible. ACE inhibitors may be used for this purpose. One study found that amino acids may help.

Mar Vista Vet has very helpful information, including information on how to treat glomerulonephritis.

Strategies for protein losing nephropathy (2001) is a presentation by Dr MS Wallace to the Atlantic Coast Veterinary Conference in which she discusses glomerulonephritis and amyloidosis.

Nephrotic Syndrome

In the worst case, glomerulonephritis may result in nephrotic syndrome. Nephrotic syndrome is not a disease in itself, but rather a collection of symptoms that may be seen as a result of the glomerular problems.

The primary symptoms of nephrotic syndrome include proteinuria, oedema and/or ascites, low albumin levels and high cholesterol levels. You may also see diarrhoea, reduced urine output, anaemia and occasionally saddle thrombus (a blood clot in the leg).

However, just as glomerulonephritis is relatively rare in cats, so is nephrotic syndrome.

Kidney Stones and Obstructions

Kidney stones may cause kidney problems. The stones may calcify, and cause damage that way, or they may lodge in the ureter, thus allowing waste products that would normally be excreted by the bladder to build up in the kidneys - this is called obstructive nephropathy.

If a cat's kidney bloodwork suddenly becomes extremely high, a kidney stone blocking the ureter may be the cause. The diagnosis can usually be confirmed via ultrasound. The ultrasound may show one small kidney and one enlarged kidney (see renomegaly).

There is more information about kidney stones on the Kidney Stones page.

Cancer - Renal Lymphoma (Lymphosarcoma)

Lymphoma (lymphosarcoma) is a type of cancer in which white blood cells called lymphocytes become cancerous and produce tumours. Some cats with lymphoma also have feline leukaemia.

Lymphoma may be found in several parts of the body; if it occurs in the kidneys, it is called renal lymphoma. It is the most common type of renal cancer in cats.  As renal lymphoma progresses, it may cause kidney disease.

Renal lymphoma can often be treated with steroids and chemotherapy, and in many cases it has a good prognosis. There are two types of lymphoma, small cell and large cell. Small cell lymphoma is slower growing and very treatable. The cat can normally be treated using chemotherapy tablets at home which reduces the cost. Large cell lymphoma is more aggressive but may still be treatable, though this normally requires weekly visits to the vet for intravenous chemotherapy to start with, with the frequency reducing and treatment stopping once the cat is in remission.

Cats tend to cope far better with chemotherapy than humans do, especially if they are given anti-nausea treatment before, during and after each chemotherapy session, so I would seriously consider this treatment if you are offered it.

Renal diseases in cats (2002) is a presentation by JP Pagès to the 27th World Small Animal Veterinary Association Congress. Section 2.5 discusses renal cancer.

The Veterinary Society of Surgical Oncology has an overview of the most common types of renal tumour.

There are more links about feline cancer, including lymphoma, on the Other Illnesses page.

Toxins: Lilies and Antifreeze

Common nephrotoxins include lilies and antifreeze, which cats may lick or eat accidentally (the taste of antifreeze is unfortunately very attractive to cats).

In most cases these cause Acute Kidney Injury, but in some cases, if the cat recovers, there may be residual kidney damage resulting in CKD.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Non-steroidal anti-inflammatory drugs are very effective at controlling pain and inflammation in cats, but unfortunately cats cannot metabolise them very well. Meloxicam is an NSAID available in both injectable and liquid (oral) form. It is approved in the UK for the ongoing treatment of arthritis in cats (and I myself used it successfully for my PKD but not CKD cat who had severe arthritis), but there are concerns that it may cause kidney problems in some cats, particularly when used at higher doses, as tends to happen in the USA where cat-sized formulations are not available.

Having said that, a study is underway at Kansas State University College of Veterinary Medicine into whether meloxicam might slow the progression of CKD in cats. You can read more about that here.

You can read more about meloxicam and other NSAIDs in the Treatments section, which includes a protocol for what to do if your cat experiences an adverse reaction.

Perinephric or Perirenal Pseudocysts

Perinephric or perirenal pseudocysts are large fluid-filled sacs that form around one or both of a cat's kidneys. They are called pseudocysts because they do not have the membrane that true cysts have. True cysts may be seen in another condition associated with CKD called polycystic kidney disease, so if your vet mentions cysts, be sure you know which type is meant.

Perinephric pseudocysts appear to be more common in male cats, and the cat may appear healthy apart from having an abdomen that is increasing in size but not usually tender to the touch. Upon examination, which is usually performed via ultrasound, the kidneys are usually enlarged.

The cysts may be treated by draining the fluid, but this is often only a temporary measure. Clinical exposures: a perinephric pseudocyst in a cat (2005) Morrow BL Veterinary Medicine states "Because of continual fluid production, needle drainage provides only temporary relief to the patient, lasting from days to months, and should be repeated as needed." However, one cat on Tanya's CKD Support Group did only need to have his cyst drained once and it never filled up again, so draining can sometimes be an effective treatment option.

Removing the wall of the cyst may be more effective, but in more severe cases it may be necessary to remove a kidney. This is a last resort because it may lead to CKD, since many cats with these cysts tend to have compromised kidneys (they are often already in early stage CKD) and/or urinary tract infections. Clinical exposures: a perinephric pseudocyst in a cat (2005) Morrow BL Veterinary Medicine states "Nephrectomy should be avoided, if possible, when underlying renal disease is present or suspected because of the potential for rapid progression of underlying chronic renal failure in the remaining kidney." However, one member of Tanya's Support Group's cat did have the surgery performed and it was a success, despite the cat already having CKD.

Pet MD says "Perirenal pseudocysts are usually not life-threatening and some cats need no treatment whatsoever. Otherwise, the fluid is surgically drained from the capsule, especially when the cat's abdomen is distended." It recommends check ups every 2-6 months.

Perinephric pseudocysts in the cat: a retrospective study and review of the literature (1999) Ochoa VB, DiBartola SP, Chew DJ, Westropp J, Carothers M, Biller D Journal of Veterinary Internal Medicine 13(1) pp47-55 reports on thirteen such cases.

Berkshire Vet tells how cysts were successfully removed from a young cat called Daisee.

Suspected Causes (Not Proven)

These are areas where research has indicated there may be a correlation between the presence of a particular factor and the development of CKD but this does not necessarily mean these factors have caused the CKD. Imagine a bank robbery: just because you happened to be present does not mean you were the robber. However, you might well need to be interviewed and ruled out as a suspect. Further research is needed.

Risk factors for development of chronic kidney disease in cats (2016) Finch NC, Syme HM & Elliott J Journal of Veterinary Internal Medicine 30(2) pp602-10 followed 148 cats in the UK between 2005 and 2009. 27 of the cats developed elevated kidney values. It concludes "Epidemiological studies, as conducted in our study, do not necessarily imply causality, but simply suggest associations."

A Vaccination Connection?

Investigation of the induction of antibodies against Crandell-Rees feline kidney cell lysates and feline renal cell lysates after parenteral administration of vaccines against feline viral rhinotracheitis, calicivirus, and panleukopenia in cats (2005) Lappin MR, Jensen WA, Jensen TD, Basaraba RJ, Brown CA, Radecki SV, Hawley JR American Journal of Veterinary Research 66(3) pp506-511 concluded that "hypersensitization with CRFK cell proteins did not result in renal disease in cats during the 56-week study".

A later study, Interstitial nephritis in cats inoculated with Crandell Rees feline kidney cell lysates (2006) Lappin MR, Basaraba RJ, Jensen WA Journal of Feline Medicine and Surgery 8(5) pp353-6, found that 50% of the cats in the study who were given normal vaccines developed interstitial nephritis according to biopsies. However, these cats were vaccinated 12 times in 50 weeks, which is obviously far more often than is normal (the current US guidelines are for cats to be vaccinated only once every three years). One group of cats in the study were given intranasal vaccines, and they did not develop any signs of interstitial nephritis.

Antibodies against Crandell Rees Feline Kidney (CRFK) cell line antigens, a-Enolase and Annexin A2 in vaccinated and CRFK hyperinoculated cats (2010) Whittemore J, Hawley J, Jensen W & Lappin M Journal of Veterinary Internal Medicine 24 pp306–313 was able to identify a number of CRFK antigens in cats vaccinated with four commercially available FVRCP (standard vaccinations) vaccines. Further research is required to determine the clinical relevance of the findings.

Please see the Treatments page for more information on the use of vaccines in cats, and discuss what is appropriate for your own cat with your vet.

Potassium Depletion

Chronic kidney disease (2007) Polzin DJ Delaware Valley Academy of Veterinary Medicine says "A particularly intriguing concept is that hypokalemia may be a cause of CKD in cats, rather than simply a consequence of it." This is because of several studies, including Chronic renal disease and potassium depletion in cats (1992) Dow SW & Fettman MJ Seminars in Veterinary Medicine and Surgery (Small Animal) 7(3) pp198-201, which suggested that all cats with CKD should be supplemented with potassium, even if they do not appear to have low potassium levels. Some people go further and believe that all older cats should be supplemented with potassium, whether they have CKD or not. 

Whilst it is true that blood tests for potassium may not accurately reflect potassium levels at the cellular level, where the potassium is needed (see Potassium for more on this), this does not automatically mean that every cat would benefit from potassium supplementation. Muscle potassium content and potassium gluconate supplementation in normokalemic cats with naturally occurring chronic renal failure (1997) Theisen SK, DiBartola SP, Radin MJ, Chew DJ, Buffington CA, Dow SW Journal of Veterinary Internal Medicine 11(4) pp212-217, found that CKD cats with normal potassium levels who were given potassium supplementation did no better than CKD cats who received a placebo.

Feeding potassium-restricted acidified diets (see below) to cats with normal renal function reduces gastrointestinal absorption of potassium and may lead to potassium depletion. I therefore would not recommend feeding such diets to older cats; and these diets should not be fed to CKD cats anyway (see Nutritional Requirements).

Do not give your cat a potassium supplement without your cat's knowledge and approval, because high potassium levels may develop quickly, particularly as the CKD progresses, and are potentially very dangerous (see Potassium).

• Dry foods

• Acidified diets

• Free feeding

• Hunting

Dry Food Diet

It is thought that feeding an exclusively dry food diet may cause chronic dehydration, which in turn may contribute to the development of CKD. This is not proven, in fact Risk and protective factors for cats with naturally occurring chronic kidney disease (2017) Piyarungsri K & Pusoonthornthum R Journal of Feline Medicine & Surgery 19(4) pp358-363 found that feeding dry cat food might actually be "a potential protective factor against CKD in cats."

Which Foods to Feed has more information on dry food versus wet.

Acidified Diets

Over the last twenty years many commercial diets have been reformulated to promote "urinary tract health", or words along those lines. Essentially, these diets are acidified, so as to reduce the risk of cats developing feline lower urinary tract disease (FLUTD). Cats with FLUTD tend to have urine that is too alkaline, and are therefore at risk of developing struvite crystals, which develop in an alkaline environment. Feeding an acidified diet reduces this risk.

Unfortunately, feeding these diets to cats who are not at risk of FLUTD may lead to urine that is too acidic. It is thought that acidified diets may be a factor in the increase in kidney stones (calcium oxalate stones), which develop in an overly acidic environment, and which in turn are a risk factor for developing CKD. The Merck Veterinary Manual states "Common management schemes that involve feeding urine-acidifying diets with reduced magnesium have reduced the incidence of feline struvite urolithiasis. Magnesium has been reported to be an inhibitor of calcium oxalate formation in rats and people; thus, the reduced magnesium concentration in feline urine may partially explain the increase in calcium oxalate stones in cats." These stones, unlike struvite, cannot be dissolved by diet - they can only be removed by surgery.

Acidified diets may also contribute to low potassium levels. I therefore would not recommend feeding such diets to older cats; and these diets should not be fed to CKD cats anyway (see Nutritional Requirements).

Free Feeding

A 2002 study, Diet and lifestyle variables as risk factors for chronic renal failure in pet cats (2002) Hughes KL, Slater MR, Geller S, Burkholder WJ, Fitzgerald C Preventive Veterinary Medicine 55(1) pp1-15, compared cats in three groups:

• free feeding with fibre;

• free feeding with Factor-2 (a composite variable composed of fiber, magnesium, protein, sodium and ash);

• and fibre alone.

The researchers concluded that free feeding was associated with increased odds of developing CKD. However, they did not simply free feed the cats; they also gave them additives. It is therefore not known whether free feeding alone would give similar results.

I myself have always free fed, and will continue to do so. In the wild, cats naturally feed multiple times a day. See Which Foods to Feed for more information on this topic.

Hunting

One study, Case control study of risk factors associated with feline and canine chronic kidney disease (2010) Bartlett PC, Van Buren JW, Bartlett AD & Zhou C Veterinary Medicine International Vol 2010, Article ID 957570, states that "There was a nonsignificant finding that the percent of diet from hunting might be positively associated with CKD, and further investigation may be warranted. This question was asked because infectious or toxicologic agents associated with hunting, such as hantavirus in rodents, may contribute to renal destruction as a hidden cause of CKD."

New Flooring

Some people on Tanya's CKD Support Group believe that new carpets and floors contain potential toxins for cats - several people have noted that their cats developed CKD shortly after new flooring was laid.

Carpets and other floor coverings may contain various volatile organic compounds, particularly in the backing. Carpet and indoor air quality (1996) Maxwell L & Hedge A Facility Planning & Management Notes, Cornell University 1(2) recommends ventilating the area where new carpet is installed for 48 - 72 hours.

Cats appear to be particularly sensitive to smells; essential oils, for example, are toxic to cats, who lack the metabolic pathways to process them. I therefore would recommend keeping cats away from new carpets and floors for several days after installation, if possible.