Toxins: Lilies or Antifreeze

Perinephric Pseudocysts

Possible (Unproven) Causes:

Selected diseases of the feline kidney (2001) is a paper presented by Dr Stephen DiBartola to the World Small Animal Veterinary Association World Congress.

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

Clinical epidemiology of kidney diseases in the cat (2008) Francey T & Schweighauser A Veterinary Focus 18(2) pp2-7 discusses the various causes of both CKD and acute kidney injury.

Hereditary/Congenital Abnormalities                                                             Back to Page Index

Polycystic Kidney Disease (PKD)

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

Renal Dysplasia and Renal Hypoplasia

In these conditions, the kidneys either do  not develop normally (renal dysplasia) or they do not develop completely (renal hypoplasia). In some cases of renal hypoplasia, known as renal aplasia, the cat has only one kidney. Cats with only one kidney tend to be male, and for some reason it is usually the right kidney which is missing.

Cats who develop CKD at an early age often suffer from renal dysplasia or renal hypoplasia. These cats often are rather small, and may be noticeably smaller than their littermates.

Merck Veterinary Manual has some information on these conditions.

Infections                                                                                                              Back to Page Index

Pyelonephritis

Pyelonephritis is a bacterial infection of the kidneys. The cat may also have a lower urinary tract infection -  in some cases, untreated lower urinary tract infections rise into the kidneys - but not always. Cats with Polycystic Kidney Disease are particularly prone to pyelonephritis, since the bacteria can burrow into the cysts. Our PKD cat, Harpsie, used to get regular bouts of pyelonephritis.

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

Feline infectious peritonitis is a serious and often fatal condition that develops in some cats who catch the corona virus. FIP is notoriously difficult to diagnose, and testing positive for the corona virus does not inevitably mean that the cat will develop FIP.

FIP occurs in two forms, effusive (wet) and non-effusive (dry). Cats with the non-effusive form of FIP sometimes have enlarged kidneys and kidney problems. However, very few cats on Tanya's Feline CRF Support Group have FIP.

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

An update on feline infectious peritonitis (2001) Horzinek MC & Lutz H Veterinary Sciences Tomorrow 1 is a rather technical article, but it has a very useful diagnostic tree.

Cornell University College of Veterinary Medicine has a good overview.

Winn Feline Foundation has information about FIP.

Newman Veterinary has information on FIP.

Inflammation                                                                                                        Back to Page Index

Glomerulonephritis and Nephrotic Syndrome

The glomeruli are very fine blood vessels in the kidneys that act as filters of waste products to produce urine. If they are damaged, blood proteins, which would normally be recycled into the bloodstream, may leak out into the urine (proteinuria). In severe cases, the resulting low levels of protein in the blood may cause weight loss and a build-up of fluids under the skin (subcutaneous oedema). 

Glomerular disease is an immune-mediated disease, and is not as common as interstitial disease. It is actually relatively rare in cats, and is usually secondary to some other condition such as an infection, inflammatory disease or diabetes. Glomerulonephritis is often managed differently to CKD - using medications to suppress the immune system may help, and one study found that amino acids may help. ACE inhibitors may also be of use for this condition because they appear to reduce the proteinuria commonly see in patients with glomerulonephritis.

Nephrotic Syndrome

In the worst case, glomerulonephritis may result in something called 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, since glomerulonephritis itself is relatively rare in cats, so is nephrotic syndrome.

Pet Place has a helpful overview of glomerulonephritis.

Dr Katherine James has information about both glomerulonephritis and nephrotic syndrome.

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.

Immune-mediated elements of renal disease (2007) Sellon RK is a presentation to the World Small Animal Veterinary Association Congress 2007.

Merck Veterinary Manual has interesting, albeit rather technical, information.

E Cure Me is a human site with information about nephrotic syndrome.

Renal Calculi (Stones) and Obstructions                                                     Back to Page Index

Renal calculi (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)                                           Back to Page Index

Lymphoma (lymphosarcoma) is a type of cancer in which white blood cells called lymphocytes become cancerous and produce tumours. Around 50% of 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.

Some of the symptoms of renal lymphoma resemble those of CKD. For example, BUN may be elevated because of internal bleeding (which may eventually also cause anaemia). Renal lymphoma may cause the kidneys to become enlarged (see renomegaly) but this is not always visible on x-ray because it is a soft tissue type tumour, though it may  show on ultrasound.

Renal lymphoma can often be treated with steroids and occasionally chemotherapy, and in many cases it has a good prognosis. Cats tend to cope far better with chemotherapy than humans do, so I would 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.

The Feline Cancer Resources Website has information and many links.

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

Toxins: Lilies and Antifreeze                                                                           Back to Page Index

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)                                       Back to Page Index

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 injectible and liquid (oral) form. Although 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), 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.

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.

Auto-Immune Diseases                                                                                    Back to Page Index

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, so it adversely affects them. In cats, the deposits are often found in the kidneys, and they eventually lead to CKD. Amyloidosis is not particularly common, but it may be found in Abyssinian cats in particular, and sometimes in Siamese and Oriental cats. Cats with amyloidosis often have proteinuria.

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.

Perinephric or Perirenal Pseudocysts                                                             Back to Page Index

Perinephric or perirenal pseudocysts are large fluid-filled sacs that form around one or both of a cat's kidneys. They 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. Removing the wall of the cyst may be more effective, but in more severe cases it may be necessary to remove a kidney. However, 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. However, the first link below does state that the prognosis is usually good if accompanying CKD is not severe and no other diseases are present.

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.

Clinical exposures: a perinephric pseudocyst in a cat (2005) Morrow BL Veterinary Medicine reports on a cat with this problem and provides a good overview of these cysts and treatment options.

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

Suspected Causes (Not Proven)                                                                         Back to Page Index

In a further study, 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 it was 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.

Regardless of these findings, I would not recommend giving any vaccines to a cat who already has CKD: vaccines are intended for healthy cats and a CKD cat is not healthy. Once Thomas had been diagnosed, our vet felt it was not wise to give him his usual vaccinations, and we agreed with her. For healthy cats, intranasal vaccines appear to be safer. 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.

Colorado State University has a report on Dr Lappin's research.

Heska has information about intranasal vaccines.

Potassium Depletion

In Chronic renal failure in cats Dr D Chew mentions that low potassium levels (hypokalaemia) "can both initiate and perpetuate chronic renal damage." One study, Chronic renal disease and potassium depletion in cats (1992) (no abstract provided) Dow SW & Fettman MJ Seminars in Veterinary Medicine and Surgery (Small Animal) 7 (3) pp198-201, 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 potassium blood tests may not accurately reflect potassium levels at the cellular level, where the potassium is needed (see Diagnosis for more on this), this does not automatically mean that every cat would benefit from potassium supplementation. A more recent study, 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 gastro-intestinal absorption of potassium and may therefore 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).

I would be wary about giving potassium to any cat with a serum potassium level over 4.4 - high potassium levels may develop quickly, particularly as the CKD progresses, and are potentially very dangerous (see Diagnosis).

• 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, but it is true that cats may benefit from more water in their diet, particularly CKD cats, as do cats with FLUTD. The Nutritional Requirements page has more information on dry food versus wet.

Acidified Diets

Many commercial diets over the last ten years have been re-formulated 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 speculated that acidified diets may be a factor in the increase in renal calculi (kidney stones) i.e. calcium oxalate stones, which develop in an overly acidic environment, and which in turn are a risk factor for developing CKD. 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.

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 Nutritional Requirements 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 CRF 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. The Carpet and Rug Institute in the USA 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.