Acute Kidney Injury and Acute on Chronic Renal Failure (AoCRF)



Pre-renal, Intrinsic and Post-renal AKI

Causes (Including Lilies and Antifreeze)

Stages of AKI






Site Overview

What You Need to Know First

Alphabetical Index


Research Participation Opportunities

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What Happens in CKD

Causes of CKD

How Bad is It?

Is There Any Hope?

Acute Kidney Injury



Nausea, Vomiting, Appetite Loss and Excess Stomach Acid

Maintaining Hydration

The Importance of Phosphorus Control

All About Hypertension

All About Anaemia

All About Constipation

Potassium Imbalances

Metabolic Acidosis

Kidney Stones



Coping with CKD

Tanya's Support Group

Success Stories



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.)



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



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)

Miscellaneous Treatments: Stem Cell Transplants, ACE Inhibitors - Fortekor, Steroids, 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



Nutritional Requirements of CKD Cats

The B Vitamins (Including Methylcobalamin)

What to Feed (and What to Avoid)

Persuading Your Cat to Eat

Food Data Tables

USA Canned Food Data

USA Dry Food Data

USA Cat Food Manufacturers

UK Canned Food Data

UK Dry Food Data

UK Cat Food Manufacturers

2007 Food Recall USA



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




Heart Problems



Polycystic Kidney Disease (PKD)


Dental Problems









The Final Hours

Other People's Losses

Coping with Your Loss



Early Detection



Canine Kidney Disease

Other Illnesses (Cancer, Liver) and Behavioural Problems

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Home > What is CKD > Acute Kidney Injury



  • 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.


Clinical epidemiology of kidney diseases in the cat (2008) Francey T & Schweighauser A Veterinary Focus 18(2) pp2-7 has some information on acute on chronic.

Renal disease - case-based approach to acute renal failure, chronic renal failure and protein-losing nephropathy (2006) Robertson J & Seguin MA discusses how to differentiate between AKI and CKD.

Patient UK explains more about this.


Symptoms                                                                                                                Back to Page Index


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).


Presentation                                                                                                            Back to Page Index


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.


Pre-renal, Intrinsic and Post-renal AKI                                                            Back to Page Index


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.

Causes                                                                                                                                               Back to Page Index


Possible causes include:


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. If your cat does ingest lilies, get him or her to the vet as soon as possible, because aggressive treatment may save the cat's life.


ASPCA has information on the dangers of lilies.

Purdue University School of Veterinary Medicine has information on lily toxicity for cats.

Cats Protection also has information on lily toxicity.

Acute renal failure caused by lily ingestion in six cats (2002) Langston CE Journal of the American Veterinary Medical Association 220(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.

Outcome following gastrointestinal tract decontamination and intravenous fluid diuresis in cats with known lily ingestion: 25 cases (2001-2010) (2013) Bennett AJ & Reineke EL Journal of the American Veterinary Medical Association 242(8) pp1110-16 found that beginning aggressive treatment within 48 hours of ingesting lilies led to a good outcome, with all the cats in this study surviving.


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.


US Food & Drug Administration - antidote for antifreeze poisoning discusses the best treatment for antifreeze poisoning.

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.

Washington State University College of Veterinary Medicine - information about antifreeze poisoning.


Renal Calculi (Stones) and Obstructions

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.


Advanced Veterinary Care Center 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.


Staging of AKI                                                                                                       Back to Page Index


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:



of Disease

Blood Values:

US Measurements (mg/dl)

Blood Values:


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.


Treatments                                                                                                               Back to Page Index


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.


Links                                                                                                                             Back to Page Index


Which is it? Acute renal failure versus chronic kidney disease (2009) is a helpful overview by Dr GF Grauer, though some may find it a little technical.

Acute renal failure in the dog and cat: causes and outcomes (2003) is a presentation by Dr LD Cowgill to the World Small Animal Veterinary Association World Congress 2003.

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.

Advanced Renal Therapies Symposium, NYC (2012) has a number of articles about AKI.

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 Focus 18(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.

Acute intrinsic renal failure - causes and prevention (2007) Chew DJ Presentation to the World Small Animal Veterinary Association World Congress 2007.



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This page last updated: 26 June 2014


Links on this page last checked: 27 March 2012





Website last updated: 26 June 2014


See above for when this particular page was last updated






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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