ON THIS PAGE:
Occult Blood Test For Gastrointestinal Bleeding
Palpation
of Kidneys
Oral Checks
Ultrasound
X-Rays
I ntravenous
Pyelogram (IVP)
Planar Renal Scintigraphy
Biopsy
Renomegaly
(Enlarged Kidneys)
HOME
Site Overview
Just Diagnosed? What You Need to Know
First

WHAT IS
CKD?
What Happens in
CKD
Causes of CKD
How Bad is It?
Is There Any
Hope?
Acute Kidney
Injury
KEY ISSUES:
PROLONGING LIFE
Phosphorus Control
Hypertension
(High
Blood Pressure)
Proteinuria
Anaemia
Potassium Imbalances
Pyelonephritis
(Kidney Infections) and Urinary Tract Infections
Metabolic Acidosis
Kidney Stones
KEY ISSUES: HELPING YOUR
CAT FEEL BETTER
Nausea, Vomiting,
Appetite Loss and Excess Stomach Acid
Maintaining Hydration
The B Vitamins (Including
Methylcobalamin)
Constipation
CAT FOOD DATA
Ways of Assessing Food Content, Including
What is Dry
Matter Analysis
How to Use the Food Data Tables
USA
Canned Food Data
USA
Dry Food Data
USA
Cat Food Brands:
Helpfulness Ratings
USA
Cat Food Brands:
Contact Details
SUPPORT
Coping with CKD
Tanya's Support Group
Success Stories
SYMPTOMS
Important: Crashing
Alphabetical List of Symptoms and Treatments
Fluid
and Urinary Imbalances (Dehydration, Overhydration and Urinary
Issues)
Waste Product Regulation Imbalances (Vomiting, Appetite Loss, Excess
Stomach Acid, Gastro-intestinal Problems, Mouth Ulcers Etc.)
Phosphorus and Calcium Imbalances
Miscellaneous Symptoms
(Pain, Hiding Etc.)
DIAGNOSIS:
WHAT DO ALL THE TEST RESULTS MEAN?
Early Detection
Blood Chemistry: Kidney Function, Potassium, Other Tests
(ALT, Amylase, (Cholesterol, Etc.)
Calcium, Phosphorus, Parathyroid Hormone (PTH) and Secondary
Hyperparathyroidism
Complete Blood Count (CBC):
Red and White Blood Cells: Anaemia and Infection
Urinalysis (Urine Tests)
Other Tests: Ultrasound, Biopsy, X-rays etc.
Renomegaly (Enlarged Kidneys)
Which
Tests to Have and Frequency of Testing
Factors that Affect Test Results
Normal Ranges
International and US Measuring Systems
TREATMENTS
Which Treatments are Essential
Fluid and Urinary Issues (Fluid Retention, Infections, Incontinence,
Proteinuria)
Waste Product Regulation
(Mouth Ulcers, GI Bleeding,
Antioxidants,
Adsorbents, Azodyl, Astro's CRF Oil)
Phosphorus, Calcium and
Secondary Hyperparathyroidism (Calcitriol)
Phosphorus Binders
Steroids,
Stem Cell Transplants and Kidney Transplants
Antibiotics and Painkillers
Holistic Treatments (Including Slippery Elm Bark)
ESAs (Aranesp, Epogen etc.) for Severe Anaemia
General Health Issues in a CKD Cat: Fleas, Arthritis, Dementia,
Vaccinations
Tips on
Medicating Your Cat
Obtaining Supplies Cheaply in the UK, USA and Canada
Working with Your Vet
and Recordkeeping
DIET & NUTRITION
Nutritional Requirements of CKD Cats
The B Vitamins (Including
Methylcobalamin)
What to Feed (and What to Avoid)
Persuading Your Cat to Eat
2007 Food Recall USA
FLUID THERAPY
Oral Fluids
Intravenous Fluids
Subcutaneous Fluids
Tips on Giving
Subcutaneous Fluids
How
to Give Subcutaneous Fluids with a Giving Set
How
to Give Subcutaneous Fluids with a Syringe
Subcutaneous Fluids - Winning Your Vet's Support
Dialysis
RELATED DISEASES
Heart Problems
Hyperthyroidism
Diabetes
Polycystic Kidney Disease (PKD)
Pancreatitis
Dental Problems
Anaesthesia
OBTAINING SUPPLIES CHEAPLY
UK
USA
Online
USA
Local (Fluids)
Canada
SAYING GOODBYE
The
Final Hours
Other People's Losses
Coping with Your Loss
MISCELLANEOUS
Prevention
Feline CKD Research, Including
Participation Opportunities
CKD Research
in Other Species
Share This Site: A
Notice for Your Vet's Bulletin Board or Your Local Pet Shop
Canine Kidney
Disease
Other Illnesses (Cancer, Liver) and
Behavioural Problems
Diese Webseite auf Deutsch
SITEOWNER (HELEN)
My
Three CKD Cats: Tanya, Thomas and Ollie
Contact Me
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Home >
Diagnosis
> Other Diagnostic Tests
Overview
-
Sometimes other tests may be appropriate, for example,
if a kidney infection is suspected, or if a young cat has CKD.
Occult Blood Test for Gastrointestinal
Bleeding
This test
is the least invasive, because initially it does not require that you take
your cat to the vet.
If you
suspect that your cat has gastrointestinal bleeding (which could be the
case if your cat's
BUN:creatinine ratio is high,
PCV or HCT is falling and
albumin and/or
MCV are low), you should take a
stool sample to your vet for testing and ask for an occult blood test.
I did this
test when Ollie was anaemic. My vet had never been asked to do this test
before, but Ollie's test was positive.
You
can buy the
EZ Detect test from pharmacies, which
tests for blood in the stool or urine (this is a human test but can also
be used for cats). You can drop some of your cat's stool in the toilet and
then follow the instructions on the packet.
Do not give
iron supplements for a couple of days before obtaining a sample for
testing. Ideally you should also feed no red meat products
beforehand, because red meat may give a false positive. I was reluctant to
restrict Ollie's diet because he was already anaemic and not eating too
well, but Ollie seemed to do well enough on chicken-based foods. Do check
what you are feeding though, many commercial foods contain more than one
meat source.
Smiths Station Animal Hospital
explains how to collect and store the stool sample.
VCA Animal Hospitals discuss the faecal
occult blood test.
Pilot study of the effect of gastrointestinal diets on fecal occult blood
testing in cats (2020) Spies KE & Slovak JE Journal of
Feline Medicine and Surgery 22(7) pp656-663 found that faecal
occult blood testing could be effective in cats, and found that feeding "a
single dry hydrolyzed, dry gastroenteric or canned hydrolyzed diet in this
study had a low chance of false-positive FOB test results, while those fed
the canned gastrointestinal diet had a significantly greater likelihood of
producing false-positive results."
Sensitivity of fecal occult blood testing in the cat
(2017)
Rudinsky AJ, Guillaumin J & Gilor C Journal of Feline Medicine and
Surgery 19(6) pp603-608 recommends that the test should be run
"in strict clinical conditions, including a controlled diet, adequate
washout period prior to testing, and no medication, which could interfere
with results."
Effect of dietary factors on the detection of fecal
occult blood in cats (2001) Tuffli
SP, Gaschen F & Neiger R Journal of Veterinary Diagnostic Investigation
13(2) pp177-9 explains more about dietary restrictions and
concludes " Both tested kits are
clinically useful for occult blood in cat feces; however, the diet fed
prior to testing must be taken into consideration, and dietary
restrictions are advisable before testing."
Palpation of Kidneys
If you visit
your vet because you are worried your cat might have CKD, the first thing
your vet will do is usually a physical examination of the kidneys by
palpating (feeling and moving) them through the skin. This will tell your
vet whether the kidneys feel small or large
and he/she may also be able to feel scar tissue.
Most CKD cats
have small, scarred kidneys, because their kidney damage is caused by
chronic
interstitial nephritis. However, some CKD cats have enlarged kidneys (renomegaly).
Kidney palpation
alone is not sufficient for a diagnosis.
Oral Checks
Many cats with
CKD have dental problems, which in some cases may even have contributed to
the development of CKD. It is therefore important for your vet to keep a
close eye on your cat's mouth and to treat any dental disease, and also to
look for mouth ulcers. Most vets will examine your cat's mouth routinely
at visits, but many dental problems are invisible to the naked eye.
There is a page
devoted to dental
problems.
Ultrasound
Ultrasounds can
be performed on various parts of the body, usually the heart, abdomen or
kidneys.
Ultrasounding
the
kidneys allows the vet to check their size and to look for certain
abnormalities in their shape or form. An ultrasound normally looks at the following parts of the kidneys:
-
renal cortex:
the outer part of the kidneys
-
renal medulla:
the innermost part of the kidneys
-
renal sinus:
the main cavity of the kidneys, which contains the renal pelvis, amongst
other things
The renal pelvis
is the top of the ureters (the tubes that lead to the bladder). It is not always looked at
on ultrasound, though it can be helpful for some diagnoses.
Ultrasounds are
not invasive and can usually be done without anaesthesia or even sedation,
so there is no need to fast the cat beforehand. The cat may need to
be shaved at the examination site (although my extremely fluffy Chinchilla
had a cardiac ultrasound without being shaved). Cold gel has to be
applied to the body to allow the equipment to work properly, which may be
a little uncomfortable when first applied (ask if you can warm it a little
in your hands first), but all my cats who have had
ultrasounds coped just fine.
Long Beach Animal Hospital has information on ultrasounds.
Pet Place explains more about abdominal
ultrasounds and mentions that sedation or anaesthesia are often not
necessary.
Renal imaging in cats (2008) Seyrek-Intas
D & Kramer M Veterinary Focus 18(2) pp23-30 discusses
ultrasounds.
Ultrasound: When to Use
Ultrasounds
should always be considered if any of the following are suspected:
enlarged kidneys
(renomegaly). Most
CKD cats have small, shrivelled kidneys.
It was
thought that ultrasounds are unlikely to be worthwhile for
the diagnosis of CKD.
Ultrasound of cats with chronic renal disease
(2007) Zwingenberger A Veterinary Radiology says ""Although ultrasound is able to detect changes in chronic renal disease,
it is not highly sensitive. Cats can have significant renal dysfunction
without ultrasonographic signs of renal disease. Conversely, many cats
cope with their chronic renal disease though they have severe
ultrasonographic changes. The history and bloodwork are important in
assessing the significance of the findings."
However, recent research indicates that all CKD cats could benefit from an
ultrasound at initial diagnosis.
Pilot study to evaluate the potential use of the
renal resistive index as a preliminary diagnostic tool for chronic kidney
disease in cats (2018) Matos I,
Azevedo P & Carreira LM Journal of Feline Medicine and Surgery
20(10) pp940-947 looked at using ultrasound to assess the use of the renal
resistive index to help diagnose CKD in cats. The study found "No
differences were found for the RRI between the left and right kidneys,
suggesting that evaluation of only one kidney is sufficient to provide an
estimate of the RRI value for both organs. RRI measurement, which can be
achieved with CDUS [colour doppler ultrasound], is an easy-to-use
diagnostic tool that, with a cut-off value of 0.639 for both kidneys, is
useful in establishing a preliminary diagnosis of CKD."
Renal pelvic and ureteral ultrasonographic
characteristics of cats with chronic kidney disease in comparison with
normal cats, and cats with pyelonephritis or ureteral obstruction
(2017) Quimby JM, Dowers K, Herndon AK, Randall EK Journal of
Feline Medicine and Surgery 19(8) pp784-790 found that the renal
pelvis
(the upper end of the ureter)
could be dilated (this is known as pyelectasia) in cats with CKD (up to
two thirds of the cats in the study had pelvic dilation of 1.2mm up to
11.5mm), as well as in cats with
pyelonephritis and kidney stones and states "these data suggest CKD cats
should have a baseline ultrasonography performed so that abnormalities
documented during a renal crisis can be better interpreted."
Therefore, if
you can afford it, I would consider an ultrasound when your cat is first
diagnosed. It is not usually necessary to sedate a cat for an ultrasound,
nor is fasting required.
Ultrasound: Who to Use
You need a
competent and experienced person to perform the ultrasound, ideally a
radiologist.
What you should know about your pet's ultrasound
exam (2009) Murray L Vet Confidential states "If your pet
ever needs an ultrasound exam, it's crucial to ensure that it's done
properly. An inadequate ultrasound can be worse than none at all, since it
often leads to misdiagnosis, which can be very dangerous for your pet. The
use of ultrasound in veterinary medicine has become very common but there
are no regulations in place to ensure that your pet’s ultrasound is
performed competently."
Sometimes you
may be offered the option to have the ultrasound performed by your vet who
will then send the images to a radiologist for feedback. Dr Murray goes
on to say
"Unfortunately many mistakes can
occur with this method. If an abnormality is not recognized by the
untrained person performing the exam, or the images are of poor quality,
the radiologist cannot make an accurate assessment of the animal. This
technique should be a last resort, for geographic areas where there is
no radiologist or internist available."
Ultrasonography of the feline kidney: technique,
anatomy and changes associated with disease
(2012) Debruyn K, Haers H, Combes A, Paepe D, Peremans K,
Vanderperren K & Saunders JH Journal of Feline Medicine and Surgery
14(11) pp794-803 has detailed information about kidney ultrasounds
in cats.
Renal ultrasound Blok BK & Hoffmann B
Ultrasound Guide for Emergency Physicians: An Introduction is about
humans and is quite technical, but it has some kidney images you may find
helpful.
Ultrasound: Findings
The kidneys of a typical healthy cat will be between 3 and 4.3 cm (around
1.25 to 1.75 inches) in length, though in some cats they may be a little
longer. The size of the cat is a factor, with females tending to have
smaller kidneys than males.
Healthy kidneys are oval or shaped like a bean, and smooth.
CKD cats tend to have small, shrivelled kidneys with an irregular shape.
Diagnostic imaging: ultrasound of cats with chronic
kidney failure not always black and white
(2008) Zwingenberger A DVM News Magazine explains how CKD kidneys look
different to healthy ones.
Ultrasound of cats with chronic renal disease
(2007) Zwingenberger A Veterinary Radiology explains more about
what normal kidneys look like on ultrasound, and what differences you may
see in CKD and end stage CKD kidneys.
Ultrasonography of the urinary tract: kidneys and
ureters (2017) Huynh E & Berry CR
Today's Veterinary Practice Nov/Dec has detailed information
about what ultrasound may show.
In cases of kidney infection (pyelonephritis), the renal pelvis may be dilated (this is known as
pyelectasis), which should be visible on ultrasound (though this may not
occur in the case of acute infections). This dilation may also occur when
kidney stones or other obstructions are present,
though will usually be more severe.
Feline chronic renal disease — acute presentation
(2007) Zwingenberger A Veterinary Radiology explains more
about how acute kidney injury looks on ultrasound, including information
on cases of obstruction or pyelonephritis.
Renal ultrasonography: kidneys big, small and
inbetween
(2011) Armbrust LJ CVC in Kansas City Proceedings
discusses the changes that may be seen in cases of enlarged kidneys.
X-Rays
X-rays can be
used to look at the kidneys and to check for kidney stones, but in most cases
palpation and, if necessary, the use of ultrasound make the use of x-rays
unnecessary.
For fractious
cats, x-rays may
require the cat to be sedated. A few members of
Tanya's CKD Support Group have been allowed to
don lead aprons and hold their cats still for the x-ray instead, but few vets permit this.
Long Beach Animal Hospital has information on x-rays.
Renal imaging in cats (2008) Seyrek-Intas
D & Kramer M Veterinary Focus 18(2) pp23-30 discusses
x-rays.
Intravenous Pyelogram (IVP)
An IVP is a special type of X-ray which uses a contrast agent to clearly
show the urinary tract.
IVPs may be used when tumours or blockages are suspected. However, the
dyes used as a contrast agent may be toxic to the kidneys, particularly if
there is a blockage. The dyes are also excreted by the kidneys, which is a
risk for cats with advanced CKD. These risks must be borne in mind when
deciding whether to have this procedure.
Urology Care Foundation has some information
about this procedure in humans.
Planar Renal Scintigraphy
This can be a helpful way of evaluating kidney function and does not require anaesthesia in most cases.
Renal scintigraphy as an early and efficient method
for detecting loss of renal function in a cat
(2021) Schaefer GC, Brose MM, Herrera Becerra JR, Mello FPS, Rovaris IB,
Berdichevski EH, Ferreira MP & da Costa FVA Journal of Feline Medicine and
Surgery Open Reports 7(2) reports on a cat whose bloodwork was
normal but who exhibited mild pain upon
palpation of the
right kidney. Renal scintigraphy showed that one kidney was working at
99% and the other at 1%.
Unfortunately renal scintigraphy is only available at a small number of
centres, so tends to only be used to assess kidney function prior to
removing a kidney because of a tumour or prior to a nephrectomy (cutting
into the kidney, e.g. to remove kidney stones).
Advanced Medical Veterinary Imaging
(2014) has a helpful overview of renal scintigraphy.
Renal imaging in cats (2008) Seyrek-Intas
D & Kramer M Veterinary Focus 18(2) pp23-30 discusses planar
renal scintigraphy.
Biopsy
A kidney biopsy is occasionally recommended, but
Proteinuria and renal disease: a roundtable
discussion
(2005) states that "Renal biopsies are only as good
as the people performing them. Good pathologic evaulation of kidney tissue
requires expertise."
Renal
biopsy: a retrospective study of methods and complications in 283 dogs and
65 cats (2005) Vaden SL, Levine
JF, Lees GE, Groman RP, Grauer GF & Forrester SD Journal of Veterinary
Internal Medicine 19(6) pp794-801 states that complications
(usually severe haemorrhaging) were reported in 18.5% of the cats in the
study, and 3.1% died.
A biopsy may be performed in cases where cancer is suspected.
IRIS treatment recommendations for CKD in
cats (2023) International
Renal Interest Society
suggest a biopsy may also be
necessary in the following situations:
-
"Renomegaly
-
"CKD in a young patient
-
"Persistent and severe proteinuria (UP/C>2.0) in a non-azotemic patient
-
"Worsening proteinuria in a CKD patient
-
"Acute kidney injury, where renal biopsy may provide a prognostic
indicator."
Since a biopsy requires an
anaesthetic, it should only be performed when absolutely necessary and the
guidelines on
anaesthesia for CKD
cats should be followed.
For general CKD
cases, it is unlikely that a biopsy will be of sufficient value to justify
the risks associated with it.
Choosing the right biopsy for the job
(2006) Wilcock B HistoVet states "With careful assessment of serum
biochemistry and urinalysis, biopsy is rarely indicated and (except for
glomerular disease) almost impossible to interpret." Discuss this in more detail with your vet in case
there may be a valid reason in your cat's case.
Renal biopsies: what are some benefits and risks
(2002) Osborne C DVM360 Magazine discusses biopsies.
Renal disease/urology (2003) Ross SR has a section entitled A special
note on renal biopsies! (scroll down a little to find it).
Renomegaly (Enlarged Kidneys)
Most CKD cats have small, scarred kidneys,
but some kidney-related conditions may cause the opposite problem of
enlarged kidneys. These conditions are discussed in more detail elsewhere
on the site:
Ultrasonography best to assess character,
consistency of renal parenchyma (2002) Hoskins JD DVM360
Magazine discusses renomegaly.
IRIS treatment recommendations for CKD in
cats (2023) International Renal Interest Society
suggest a biopsy may also be
necessary in cases of renomegaly.
Pet MD has an overview of renomegaly.
Renal ultrasonography: kidneys big, small and
inbetween (2011) Armbrust LJ CVC in Kansas City Proceedings
discusses the changes that may be seen on ultrasound in cases of
enlarged kidneys.
Hydronephrosis
Hydronephrosis
occurs when the kidneys are enlarged with urine because of obstruction of the ureter, which prevents
the urine from passing from the kidneys through to the bladder. This is commonly caused
by kidney stones. Cats with
acute kidney
injury may have enlarged kidneys, often (but not always) because of
such an obstruction.
Pet Place has information on
hydronephrosis.
National Kidney Foundation has some
information about hydronephrosis in humans.
Big Kidney Little Kidney
Occasionally a cat will have one small kidney and one large kidney, a
condition known with startling originality as "big kidney little kidney
syndrome". This is commonly caused by
stones or obstructions. One
kidney becomes damaged by stones and shrinks, while the other increases in
size in order to compensate and take on some of the work of the damaged
kidney.
Acute uremia in cats (2008) Ross S Veterinary
Focus 18(2) says "Sustained obstruction leads to fibrosis and atrophy
of the corresponding kidney and compensatory
hypertrophy of the contralateral kidney. The
disease remains clinically silent until obstruction
of the contralateral ureter occurs. This process
explains the classic "big kidney-little kidney"
scenario typical of many cats diagnosed with acute ureteral obstruction."
Evaluation of and the prognostic factors for cats with big
kidney-little kidney syndrome (2021) Wu Y-T, Hung W-C, Huang
P-Y, Tsai H-J, Wu C-H & Lee YJ Journal of Veterinary Internal
Medicine 35(6) pp2787-2796 found that cats with big
kidney little kidney syndrome had worse kidney bloodwork values than
the control cats, and that a greater difference in size between the
kidneys made a blockage more likely, but presence of the syndrome
was not a prognostic indicator for survival.
Feline big kidney, little kidney: acute kidney
injury in the cat (2015) Costello
M
Presentation to the World Small Animal
Veterinary World Congress discusses cats who develop acute kidney
injury and big kidney little kidney syndrome secondary to kidney stones.
Cats with chronic renal failure (CRF) -- how different
than CRF in dogs? (2007) Chew DJ and DiBartola
SP
Presentation
to the World Small Animal
Veterinary World Congress mentions big kidney little kidney syndrome.

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This page last updated: 07 June 2025
Links on this page last checked: 07 June 2025
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