Acute kidney
injury (AKI), previously known as acute renal failure (ARF), is a
serious form of kidney failure which usually comes on suddenly and which is often
triggered by a particular event or "insult" to the kidneys.
AKI is
difficult to treat but in some cases the cat may make a full recovery. In
other cases, the cat will be left with residual kidney damage.
It is possible
to have AKI and CKD simultaneously.
Acute on Chronic Kidney
Disease
It is possible
to have AKI and CKD simultaneously. This is often referred to as acute on chronic
renal failure or AoCRF, but I expect the name will be changed to AoCKD. As
the name suggests, it occurs when already chronically damaged kidneys
suffer an acute injury, such as a
kidney infection (pyelonephritis) or when
hyperthyroidism
is over-treated. Cats
with AoCRF often crash.
With hindsight,
you may realise that your CKD cat was exhibiting subtle signs of illness
such as increased drinking and urination, poor appetite and weight loss.
In contrast,
since AKI comes on suddenly, there may have been no signs at all of
illness previously, so you will probably notice a dramatic change in your
cat. AKI cats often look lethargic, stop eating and vomit. They may
urinate more, less or not at all (not urinating at all is a medical
emergency, as AKI is generally).
Cats with AKI
will often present with extremely high bloodwork, with creatinine often
over 10 USA (850 international), although it may even be twice as
high as that. They usually have
metabolic acidosis. At initial diagnosis, they may have
low calcium
levels, which may then rise as treatment is begun, to such an
extent that they may then become too high. Unlike cats with CKD with such high bloodwork, however,
AKI
cats are often not anaemic, at least not initially.
They may exhibit
reduced
urination (which is sometimes the cause of the AKI if there is a
reason for it such as a kidney stones), and this can cause potassium levels to rise to dangerously
high levels (high potassium levels are known as
hyperkalaemia).
For cats with
AKI, it
is often worth getting an
ultrasound
performed to see if this can shed some light on the cause - cats with CKD
tend to have small, shrunken kidneys, whereas cats with AKI often have
enlarged kidneys.
Like CKD, AKI
can be divided as follows, depending upon the location of the problem:
pre-renal
("before" the kidney):
this
usually occurs when something disrupts blood flow to the kidneys.
Possible causes include low blood pressure, the use of
NSAIDs or
ACE inhibitors. It is usually reversible once the problem has been
treated.
intrinsic ("at" the kidney):
this means
the injury is caused at the kidney itself. Possible causes include
infections, toxins or glomerulonephritis.
This is the hardest to treat, but it may be possible, depending upon
the cause.
post-renal
("after" the kidney):
this means
the problem has arisen lower down the urinary tract, after
the blood has already flowed through the kidneys. The usual cause is an
obstruction (e.g. kidney stones), which stops urine being passed and
causes toxin build up. If the problem can be resolved, the cat can
make a full recovery.
Most types of lily are extremely toxic to cats. It is not necessary for
the cat to nibble on the leaves - even if the cat simply brushes against a
tiny amount of pollen, then later licks that area, it can cause AKI.
Do what I do: don't allow lilies in your home.
Acute renal failure caused by lily ingestion in six
cats (2002) Langston CE Journal of the American Veterinary
Medical Association220(1) pp49-52 reports on six cats who
developed AKI after ingesting Easter or tiger lilies. Three cats survived,
two died, and one was put to sleep with no treatments being attempted. The
chance of survival was lower in cats with reduced or no urination.
Antifreeze
(Ethylene Glycol)
Anti-freeze is a common cause of acute kidney injury because unfortunately
cats seem to like the taste of it. Cats may sometimes
appear to recover, but will then become ill once again; therefore it is critical to
seek veterinary treatment as early as possible, even if the cat appears to
be recovering. Early treatment greatly influences the cat's chances of
survival.
Pet Place
- three pages of detailed information on antifreeze poisoning. No need to
register to read the article, just click Close on the registration box
which initially blocks you from viewing the article.
Renal calculi
(kidney stones) may cause acute kidney injury. This usually happens if they lodge in the ureter
(the tube that leads from the kidneys to the bladder) and allow waste
products that would normally be excreted by the bladder to build up in the
kidneys - this is called obstructive nephropathy. The diagnosis can usually be confirmed via
ultrasound. The ultrasound may show one small kidney and one enlarged kidney (see
renomegaly).
See Kidney Stones
for more information.
Kidney Infections (Pyelonephritis)
Cats with acute
kidney infections may develop acute kidney injury. In some cases,
successfully treating the infection will lead to the cat making a full
recovery. Kidney infections may need to be treated with intravenous
fluids. A lengthy course of antibiotics is also necessary in most cases.
See
Urinalysis for more information.
describes the case of a seven month old cat with CKD who developed acute
kidney injury on top of the CKD because of a kidney infection.
NSAIDs, Such as
Meloxicam
(Metacam)
Meloxicam is a
non-steroidal anti-inflammatory drug
(NSAID) available in both injectible and liquid
(oral) form. In the USA meloxicam is only approved for use in cats
in its injectible form. This is because it is intended to be a one-off
treatment as a painkilling injection following surgery. In
Europe it is approved in both the
injectible version (for one-off use in cats following surgery) and in
oral form (for longer term pain management
e.g. for use in cats with arthritis).
Unfortunately in some cases meloxicam appears to
have caused permanent damage to the kidneys, with the
result that a number of cats seem to have developed acute
or chronic kidney problems after taking it.
The risk of this occurring appears to be dosage-related.
There is more information on meloxicam in the
Treatments section.
The
International Renal Interest Society (IRIS) provides a
classification system
for CKD in cats, and on page 81 of
Clinical staging of acute kidney injury
(2012) Cowgill LD Presentation to the Advanced Renal Therapies
Symposium, NYC , Dr Cowgill discusses a proposed new IRIS
classification system for acute kidney injury, as follows:
Stage
of Disease
Blood Values:
US
Measurements (mg/dl)
Blood Values:
International
Measurements (µmol/L)
Clinical Description
Stage 1
Creatinine below 1.6
Creatinine below 140
- Non azotaemic AKI or volume-responsive
AKI
- Historical, clinical, laboratory, or
imaging evidence of renal injury
-
Non azotaemic
increase in serum creatinine of more than 0.3 mg/dl within 48 hours
Stage 2
Creatinine
between
1.7 and 2.5
Creatinine between
140
and 220
Mild AKI: Historical,
clinical, laboratory, or imaging evidence of AKI and mild static or
progressive azotaemia
Stage 3
Creatinine
between
2.6 and 5.0
Creatinine
between
221 and 439
Moderate to Severe AKI:
Documented AKI and increasing severities of azotaemia and functional
renal failure
Stage 4
Creatinine between 5.1 and 10.0
Creatinine between 440
and 885
Stage 5
Creatinine over 10.0
Creatinine over 885
Each stage is
also sub-staged depending upon whether the cat is producing no urine or
only a small amount of urine and whether the cat needs some kind of
dialysis.
Dr Cowgill
points out that things can change suddenly with AKI, so these stages are a
snapshot. Do not give up hope if your cat is in the higher stages, things
may change with appropriate treatment. He states "Animals
recognized and managed with IRIS AKI Stages I and II may regain adequate
renal function within 2 to 5 days, forestalling life-threatening azotemia
and electrolyte disorders and usually need only short-term support. Those
with higher IRIS Stages of AKI at presentation or whose IRIS AKI stage
progresses during hospitalization may require weeks of supportive care
before the onset of renal repair. Animals with severe kidney failure, IRIS
AKI Stage IV or V, may die within 5 to 10 days despite appropriate
conventional management unless supported with renal replacement therapy
for an indefinite time."
Dr Cowgill gives examples of cats in each stage, including a cat (Example
3) with
pyelonephritis who improved greatly with appropriate treatment.
Example 5 is a cat with lily toxicity who made a full recovery.
AKI caused by
toxins is usually
treated with several days of hospitalisation on
intravenous
fluids. Various medications may also be given to treat concurrent
problems such as high potassium levels or metabolic acidosis. Do not
accept just one day of treatment, most cats need several days.
Cats with kidney stones
usually have calcium oxalate stones.
These cannot be dissolved through diet, so are usually treated initially with IV fluids
and diuretics in an attempt to flush the
stones out. See the
Kidney Stones page for more information.
Urinary tract
blockages may also be caused by the opposite problem,
struvite
crystals. This type of blockage also needs to be treated with
hospitalisation on IV fluids and in some cases may require surgery, but
following the initial crisis it often be managed with dietary
modifications at home.
The
Treatments section
gives details of the recommended protocol for
treating acute kidney injury associated with the use of meloxicam.
Although AKI
can be difficult to
treat, if the cat survives the initial crisis, he/she can often regain
much or sometimes all of his/her normal kidney function. However, sometimes cats
who experience AKI will have some residual damage, and will be
left with CKD.
Pet Place - helpful information about acute
kidney injury. No need to register to read the article, just click Close on the
registration box which initially blocks you from viewing the article.
Renal
disease/urology (2003) is a paper by Dr S
Ross which has a helpful section on differentiating AKI from CKD. It
also talks about the symptoms of acute on chronic, where a cat who already
has CKD suddenly develops AKI on top, often while the patient is already
in ICU.
Acute uremia in cats (2008) Veterinary
Focus18(2) is a more recent paper by Dr Ross.
Dr
Katherine James - a site by a feline nephrologist who
recommends this website to those dealing with CKD. Also technical but useful.
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.
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appears to be in pain or distress, do not waste time on the internet,
contact your vet immediately.
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