I am including this
information because so many people seem to blame themselves for their
cat's illness, when in truth CKD is rarely avoidable - as the
What
Happens in CKD page mentions, around 10% of cats over the age of ten will
develop CKD, with as many as 30% of cats over the age of 15 having the
disease.
This page is
divided into known causes of CKD and possible causes.
The possible causes
section is just that at this point, possible causes. This section
is not there to make you feel guilty about, say, your food choices. There is no
hard evidence that any of these possibilities truly do cause CKD, although
the anecdotal evidence is stronger for some than for others.
On the
left is a list of this page's contents.
Introduction
Many people who
contact me want to know what has caused their cat's CKD because they are
worried that they did something wrong, and want to ensure they do not do
the same thing with their other cats.
CKD is not
actually that simple. There are a multitude of possible causes, which I
outline below, but in many cases you will never find out the most likely
cause in your cat's case.
Try not to feel
guilty because the cause is unlikely to be anything within your
control. Most cats with CKD have changes in their kidneys known as chronic interstitial nephritis, and this is largely
related to old age, affecting around 10% of
cats over the age of ten, and as many as 30% of cats over the age of 15.
So unless you have mastered the art of arresting aging in your cat (and if
you have, please let me know immediately), the chances are it is just a
combination of inflammatory processes, the
passage of time, and bad luck.
Renal fibrosis in feline chronic kidney disease:
known mediators and mechanisms of injury
(2015) Lawson J, Elliott J, Wheeler-Jones C, Syme H & Jepson R
The Veterinary Journal 203(1) pp 18-26 says "It is thought
that the intra-renal environment in CKD is significantly pro-fibrotic,
leading to continued production of pro-inflammatory and pro-fibrotic
cytokines and the perpetuation of the wound healing response rather than
its resolution. The factors with the most influence on maintaining this
state and which have undergone the most investigation to date are believed
to be proteinuria,
chronic inflammation, hypoxia, ageing and
hyperphosphataemia."
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 Association244 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 Medicine30(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 PracticeOct 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."
Incidence of the Various Causes
Renal Disease
(2006)
Polzin DJ
Delaware Valley Academy of Veterinary Medicine
says that of cats with renal disease:
Renal diseases in cats (2002) Pagčs JP
Presentation to the27th World Small Animal Veterinary
Association Congress discusses the various causes of CKD.
Chronic Interstitial
Nephritis
This is the
most commonly seen type of kidney problem, so when a vet says a cat has
CKD, s/he often means chronic interstitial nephritis.
Cats with chronic
interstitial nephritis have small, shrivelled kidneys with scar tissue.
The
What
Happens in CKD page
explains why this occurs.
Hereditary/Congenital Abnormalities
There are a number of inherited or congenital conditions which may leas to
CKD in cats.
Inherited kidney diseases in dogs and cats
(2005) Lees GE Presentation to the Tufts' Canine and Feline Breeding and
Genetics Conference has a good overview of these conditions.
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
These conditions are quite rare in cats but
Feline hereditary and congenital kidney disease
(2013)
Suárez Rey M Veterinary Focus23(3) pp17-25 states that
renal dysplasia is more common in Persian and Norwegian Forest cats.
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. A small stature may also be a sign of FIP
(see below). Unfortunately young cats
who develop CKD are often diagnosed at a relatively
late stage because nobody expects a young cat to develop CKD. Treatment is
as for CKD generally.
R
enal
Aplasia (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).
Cats with one
kidney may have a normal lifespan.
Humans born with one kidney seem to do well:
The congenital and acquired solitary kidney
(2003) Shapiro E, Goldfarb DA & Ritchey ML Reviews in Urology
5(1) pp2–8 says "Unilateral renal agenesis is compatible with normal
longevity and does not predispose the contralateral kidney to
greater-than-normal risk; nevertheless, patients should have annual
surveillance, including a blood pressure measurement, serum creatinine if
not initially normal, and urinalysis to detect proteinuria." It goes on to
say "Overall survival was not affected by URA unilateral renal agenesis].
URA is compatible with normal longevity and does not predispose the
contralateral kidney to greater-than-normal risk."
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 Medicine29(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."
Overview of amyloidoses (2016) Tizard I
The Merck Veterinary Manual has an overview of amyloidosis.
Strategies for protein losing nephropathy
(2001) Wallace MS Presentation to theAtlantic Coast
Veterinary Conference in which she discusses glomerulonephritis and
amyloidosis.
This is a rare
condition in which the kidneys are damaged by urine flowing backwards into
the kidney. A genetic form of this has recently been identified in
Ragdolls by researchers in Finland.
Health and behavioral survey of over 8000 Finnish
cats (2016) Vapalahti K, Virtala
A-M, Joensuu TA, Tiira K, Tähtinen J & Lohi H Frontiers in Veterinary
Science3(70) pp1-16 states that Ragdolls were the only breed
reported to have the disease.
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.
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 a
coronavirus, which then mutates into FIP. (Although it belongs to the
coronavirus family, FIP is not the same as Covid-19).
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 coronavirus does not inevitably mean that the cat will develop FIP (the majority
of cats test positive for the coronavirus 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 ratio 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 was worse,
because there was so little I could do and so little hope.
Until very recently, there were very few treatments available for FIP, and
those that were available worked for some cats (often only for a short
while) but not for others, so FIP was generally considered to be fatal. (I
tried feline interferon and polyprenyl for Lily, but without success).
This changed
when a treatment known as GS-441524 was assessed in 31 cats with FIP, as
discussed in
Efficacy and safety of the nucleoside analog
GS-441524 for treatment of cats with naturally occurring feline infectious
peritonitis (2019) Pedersen NC,
Perron M, Bannasch M, Montgomery E, Murakami E, Liepnieks M & Liu H
Journal of Feline Medicine and Surgery21(4) pp271-281. Four of
the cats were put to sleep within 2-5 days of starting the study, and a
fifth was put to sleep during the study. However, of the 26 cats who
completed the study, eighteen remained healthy after one 12 week course of
treatment, and although the eight other cats relapsed, repeated courses of
treatment were effective, to such an extent that 24 cats remained healthy
(one cat died of heart disease, and the other of neurological problems
caused by the FIP).
GS-441524
therefore is widely considered to be a breakthrough treatment for FIP,
being both safe and effective, but tragically it is not commercially
available as yet and, since it is patented by Gilead Sciences, which is
currently focusing on treatments for Covid-19 in humans, it is not known
whether it ever will be. Some people are therefore purchasing illegal
versions of the treatment, usually from China, with varying degrees of
success.
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.
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 Focus23(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."
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).
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.
VCA Hospitals has a good
overview of glomerulonephritis in cats.
Pet
Place has a helpful overview of glomerulonephritis.
Strategies for protein losing nephropathy
(2001) Wallace MS Presentation to theAtlantic 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.
It appears that
dental problems may be linked to an increased risk of other health issues.
Although the precise mechanism is not known, it appears that in
humans there may be a link between the oral bacteria associated with poor
dental hygiene and heart disease.
Colgate
reports on this.
A similar link
is thought to exist in cats.
Littleton West Animal Hospital
states that dental disease "not only affects the mouth, but
can also lead to more serious health problems such as heart, lung, and
kidney disease."
Risk factors for development of chronic kidney
disease in cats (2016)
Finch NC, Syme HM & Elliott J Journal of Veterinary Internal Medicine30(2) pp602-10 states "It
is possible that oral inflammation may lead to kidneys damage through
unknown mechanisms" and concludes
"Our study suggests independent associations
between both vaccination frequency and severity of dental disease and
development of CKD" but states that further studies are necessary to
investigate why this might be the case.
Some cats with periodontal disease who need dental treatment under
anaesthesia may develop CKD shortly afterwards.
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 Association244 pp320–327 found that "Risk
factors for CKD in cats included ... prior periodontal disease
or cystitis, anesthesia or documented dehydration in the preceding year."
A more recent study appeared to support these earlier findings.
Survival analysis to evaluate associations between
periodontal disease and the risk of development of chronic azotemic kidney
disease in cats evaluated at primary care veterinary hospitals
(2018)
Trevejo RT, Lefebvre SL, Yang M, Rhoads C, Goldstein G & Lund EM
Journal of the American Veterinary Medical Association252(6)
pp710-720 evaluated cats at 829 hospitals over a period of more
than eleven years, comparing cats with periodontal disease to cats without
periodontal disease. The study found that periodontal disease (PD) "was
associated with increased risk of CKD; risk was highest for cats with
stage 3 or 4 PD. Risk of CKD increased with age. Purebred cats had greater
risk of CKD than mixed-breed cats. General anesthesia within the year
before study exit and diagnosis of cystitis at any point prior to study
exit (including prior to study entry) were each associated with increased
CKD risk. Diagnosis of diabetes mellitus or hepatic lipidosis at any point
prior to study exit was associated with decreased CKD risk."
Whilst it is true that
hypertension is more common in cats with these conditions, it is gradually
becoming clear that primary hypertension does exist in cats, and may in
fact contribute to the development of CKD.
If the blood vessels within the kidneys are damaged because of
hypertension, eventually CKD can result. The
National Institute of Diabetes and Digestive and
Kidney Diseases explains more about this.
Feline hypertension: Part 1
(2012) Atkins C
says
"adding to the confusion in
understanding the pathogenesis of hypertensive renal disease, renal
disease begets hypertension and hypertension begets renal disease."
This topic is
covered in detail on the
Hypertension page.
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.
BUN
may be elevated because of internal bleeding (which may eventually also
cause
anaemia), as may lymphocytes. 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. A biopsy is necessary for a definitive diagnosis
but many people do not bother and treat presumptively.
There are two
types of lymphoma:
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) Pagčs JP
Presentation to the 27th World Small Animal Veterinary
Association Congress. Section 2.5 discusses renal cancer.
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, primarily 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
Medicinestates "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, and a couple of
people on Tanya's CKD Support Group have had this done successfully, 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
Medicinestates "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.
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 Medicine30(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."
In 2002 a tentative connection between feline
vaccinations and CKD was mooted.
The connection arises because feline vaccines are grown on kidney cells
known as Crandell Reese Feline Kidney (CRFK) cells. It has long been known
that growing the vaccines in this way produces some unidentified
antibodies in addition to those required for the vaccine, but it was only
discovered in 2002 that the unidentified antibodies were to renal
tissue. These additional antibodies occur in all modified live or killed
vaccines, but do not occur with intranasal vaccines. In the UK, live
vaccines are usually used.
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.
Risk factors for development of chronic kidney
disease in cats (2016)
Finch NC, Syme HM & Elliott J Journal of Veterinary Internal Medicine30(2) pp602-10 states "A large proportion of the feline
population receives regular vaccinations and, based on findings from
previous studies described above, this practice may be considered a
potential risk factor for CKD in cats." It concludes
"Our study suggests independent associations
between both vaccination frequency and severity of dental disease and
development of CKD" and states that further studies are necessary to
investigate why this might be the case.
in 2012 Dr
Lappin stated that in his research cats who developed antibodies did
not go on to develop CKD. He recommends that core vaccines should continue
to be given to healthy cats in accordance with the
American Association of Feline Practitioners
vaccination guidelines.
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.
Feline
Morbillivirus (FeMV)
Researchers
have found that a recently discovered virus may 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 SBMC
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 Diseases22(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 Genes51(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.
Novel feline viruses: emerging significance of
gammaherpesvirus and morbillivirus infections in cats
(2019) Beatty JA, Sharp CR, Duprex WP & Munday JS Journal of
Feline Medicine and Surgery21(1) pp5-11 reviewed earlier
studies and says that morbillivirus has been found in up to 52.9% of cats,
both healthy or with CKD, in one study in South America. "Naturally
acquired FeMV may be an asymptomatic and self-limiting viral infection, or
it may result in disease in cats that has previously been attributed to
other causes or considered to be idiopathic," but add that causation has
not yet been proven.
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.
Overall there is not sufficient evidence to support the theory that low
potassium levels may cause CKD.
Chronic kidney disease
(2007) Polzin DJ
Delaware Valley Academy of Veterinary Medicine says
"These findings support the concept that reduced renal function
precedes development of hypokalemia."
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 vet's knowledge
and approval, because high potassium levels may develop quickly,
particularly as the CKD progresses, and are potentially very dangerous
(see Potassium).
Proton Pump Inhibitors
There is some evidence that proton pump inhibitors (such as omeprazole,
sometimes used in CKD cats) may be a factor in the development of CKD in
humans. This is discussed in more detail on the
Appetite Loss, Nausea and Vomiting page.
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
and
Surgery19(4) pp358-363 found that feeding dry cat food might
actually be "a potential protective factor against CKD in cats."
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.
Urolithiasis in Small Animals (2913)
Brown SA 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).
Arsenic is water soluble and
accumulates in organs such as the liver and kidney, where it is relatively
toxic either by itself or via interactions with other catalytic metals
such as iron and copper. High urinary arsenic is associated with increased
risk of CKD... Arsenic may therefore bio-accumulate in the tissues of
animals such as fish that inhabit these waters and in the animals that
consume these fish sources such as the domestic cat. It remains to be
determined if relatively high, long-term arsenic intake predisposes the
domestic cat to chronic kidney disease or whether high intake of other
metals that are also prevalent in fish may also have an effect, such as
mercury."
Foods With a High Phosphorus Content
Although it is well documented that a
high phosphorus intake
is not appropriate for CKD cats (it can make the CKD progress faster, can
make the cat feel unwell, and may lead to
secondary hyperparathyroidism), in recent times there is also some
debate as to whether a high dietary phosphorus intake may be a factor in
the development of CKD. This is discussed in more detail on the
Prevention
page.
free feeding with Factor-2 (a composite variable composed of fibre,
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
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 InternationalVol 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 University1(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.
TREATING YOUR CAT WITHOUT VETERINARY ADVICE CAN BE
EXTREMELY DANGEROUS.
I have
tried very hard to ensure that the information provided in this website is
accurate, but I am NOT a vet, just an ordinary person who has lived
through CKD with three cats. This website is for educational purposes
only, and is not intended to be used to diagnose or treat any cat. Before
trying any of the treatments described herein, you MUST consult a
qualified veterinarian and obtain professional advice on the correct
regimen for your cat and his or her particular requirements; and you
should only use any treatments described here with the full knowledge and
approval of your vet. No responsibility can be accepted.
If your cat
appears to be in pain or distress, do not waste time on the internet,
contact your vet immediately.
This site was
created using Microsoft software, and therefore it is best viewed in
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This site is a labour of love, from which I do not make
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If you wish to
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