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Home > Symptoms > Body Fluid Regulation and Urinary Issues



  • This page discusses the various symptoms that are associated with the regulation of body fluid, including both dehydration and overhydration.

  • It also discusses symptoms associated with urination, such as urinary tract infections, incontinence and proteinuria (protein in the urine).

  • For a complete list of CKD symptoms, or to look up a symptom which is bothering you, please see the Index of Symptoms and Treatments, where all the symptom are listed alphabetically, with quick links to each individual symptom and appropriate treatment options.

Symptoms Associated With Dehydration


Healthy cats produce concentrated urine but the ability to do this gradually deteriorates in a CKD cat as the kidneys fail. Although the cat will drink more in an attempt to compensate for the increased urination, eventually it becomes impossible to maintain a balance, and dehydration occurs.


Many people believe that dehydration means the loss of water from the body. However, it actually means the loss of both fluids and electrolytes salts which the body needs in order to function properly.


If you've ever been dehydrated, you know how awful it feels like a bad hangover, with a dreadful headache and stomach ache. Dehydrated cats often stop eating, which then makes them even more dehydrated because they are not obtaining any fluid from their food. To make matters worse, cats who do not eat are at risk of developing a potentially life-threatening condition known as hepatic lipidosis; Mar Vista Vet has more information about this. Although most dehydrated cats drink more (see below), if they feel really bad they may stop drinking, which increases the risk of a crash. Therefore, it is important to detect and treat dehydration as quickly as possible.


Pet Place has some information about dehydration in cats.


Checking For Dehydration

It is not possible to diagnose clinical dehydration until the cat is already at least 5% dehydrated, so by the time you see signs, you already have a definite problem.  Fluid therapy: calculating the rate and choosing the correct solution (2010) Terry B Firstline describes the likely degree of dehydration based on physical signs.


You should regularly check your cat's hydration levels: the most common method is to pinch the skin, usually at the scruff of the neck - the skin should fall back into place immediately. Most CKD cats experience some degree of dehydration so the skin may not fall back as quickly as in a healthy cat, but if it takes a few seconds you should look into improving your cat's hydration.


Another way to check is to feel your cat's gums: they should look shiny and feel slick. If they feel sticky, your cat is probably dehydrated.


PetCoach has some information about how to use these two assessment methods.


Virtuavet has photos showing how the skin looks with varying degrees of dehydration.


Some people weigh their cats daily, finding this a good guide to their cat's degree of hydration.  


Increased Urination (Polyuria)

The cat is an unusual animal in that it has the ability to concentrate its urine, a little like a camel; this is believed to be a legacy of its African heritage. However, in cats with CKD, this ability gradually disappears, and cats then produce a very dilute urine: the urine looks weaker in colour, has little odour, and the cat will often produce copious amounts. 


Practical urinalysis in the cat: 1: urine macroscopic examination 'tips nd traps' (2016) Reppas G & Foster SF Journal of Feline Medicine and Surgery 18(3) pp190-202.states that healthy adult cats produce 18-28ml/kg of urine a day, whereas cats with polyuria produce more than 40 ml/kg a day.


Cats with chronic pyelonephritis (a kidney infection or inflammation) may exhibit polydipsia and polyuria. Polyuria and polydipsia in dogs and cats (2013) Grauer GF Clinician's Brief Mar 2013 states "Chronic pyelonephritis is more difficult to recognize because clinical signs may be subtle or absent. Polyuria and polydipsia are frequent."


Cats with elevated calcium levels (hypercalcaemia) may be polyuric.


Polyuria and polydipsia: streamlining your veterinary diagnostics (2020) Todd-Jenkins K Presentation to the Fetch DVM360 Conference explains more about polyuria and polydipsia.


The ins and outs of polyuria and polydipsia (2003) Osborne CA DVM360 Magazine discusses polyuria.


Increased Drinking (Polydipsia)

The increase in urination that occurs in CKD leads the cat to drink more and more in an attempt to avoid becoming dehydrated. Some cats, like Tanya, develop new behaviours, such as drinking from showers or gutters, or hanging around sinks and begging for fresh running water from the tap. Some cats like to play with their water bowls from an early age, but some CKD cats develop a bit of an obsession with water, and may play with their water bowl or paw at the water.


Cats with chronic pyelonephritis (a kidney infection or inflammation) may exhibit polydipsia and polyuria. Polyuria and polydipsia in dogs and cats (2013) Grauer GF Clinician's Brief Mar 2013 states "Chronic pyelonephritis is more difficult to recognize because clinical signs may be subtle or absent. Polyuria and polydipsia are frequent."


Cats with elevated calcium levels (hypercalcaemia) may be polyuric, as may cats with  diabetes.


Increased drinking may also be a symptom of gastric hyperacidity. The cat may drink more because, according to A glass of water immediately increases gastric pH in healthy subjects (2008) Karamanolis G, Theofanidou I, Yiasemidou M, Giannoulis E, TriantafyllouK & Ladas SD Digestive Diseases and Sciences 53(12) pp3128-3132, drinking water may briefly (only for a few minutes) reduce levels of stomach acid.


Polyuria and polydipsia: streamlining your veterinary diagnostics (2020) Todd-Jenkins K Presentation to the Fetch DVM360 Conference explains more about polyuria and polydipsia.


The ins and outs of polyuria and polydipsia (2003) Osborne CA DVM360 Magazine discusses polydipsia.


Sneezing and Congestion

This may be a sign of an upper respiratory tract infection (a cold or "cat flu"). CKD cats may be prone to these viral infections because they are immune-compromised; plus CKD cats may be visiting the vet more often and therefore can be exposed to more viruses.


However, if your cat has no other signs of an upper respiratory tract infection, then the sneezing may be caused by dehydration - the nasal passages of a dehydrated cat will be drier and therefore more susceptible to irritation, such as dust.


Dental problems may sometimes cause sneezing.


Another possible cause is the long-term use of cyproheptadine, which may make the nasal tissues swell as the drug becomes less effective.


Sneezing and snorting what should I do? (2001) McKiernan B Presentation to the World Small Animal Veterinary Association World Congress discusses these symptoms.



In addition to concentrating urine, a cat's body also tries to conserve water by reabsorbing it from the stool through the intestinal wall. This mechanism is very efficient, and remains so even in CKD cats, and since CKD cats are largely on the edge of dehydration most of the time, the intestine will wring every drop of water out of the stool that it can, leaving it quite dry. The lack of moisture as a lubricant makes it more difficult for the cat to have bowel movements and can lead to constipation. 


Low potassium levels may also cause constipation, as may high calcium levels.


See Constipation for more information.


Weight Loss

This is a common symptom of CKD, and was the first sign with both Tanya and Thomas. Not only did they lose weight, but their spines became very bony (and their coats became dry with dandruff).


Weight loss may occur because as the cat drinks and urinates more, s/he may develop proteinuria. Weight loss can also be associated with phosphorus imbalances or metabolic acidosis (particularly when accompanied by a bony spine), or may be a symptom of other diseases such as diabetes or hyperthyroidism. Other possible causes include IBD (Inflammatory Bowel Disease) or cancer.


Pet Place has some information on weight loss in cats.


Dull Coat/Dandruff/Spiky Fur

This reflects the general loss of condition of a CKD cat, and is also influenced by dehydration. The body is fighting a tough battle with CKD and concentrates its efforts on its more critical functions; a glossy coat is not one of them.


Occasionally spiky fur may indicate a lack of essential fatty acids, or may be a symptom of hyperthyroidism.


Other Signs of Dehydration

  • Recently sunken eyes may indicate dehydration, as may vomiting.

  • Cracked paw pads are also occasionally seen, and litter may stick to the cat's paws.

  • Sometimes a cat with dehydration hangs his/her head over the waterbowl, though more commonly that is a sign of gastric hyperacidity.

  • The cat may also grind his/her teeth, or lick his/her lips.

  • Increased vocalisation in elderly cats (2015) Gunn-Moore DA European Journal of Companion Animal Practice 25(3) pp20-29 states "Chronic kidney disease can result in increased vocalisation when associated systemic hypertension causes cerebral vascular compromise (as in CDS). It can also occur when polyuria without adequate access to water cause cerebral dehydration, when polydipsia/polyuria predisposes to a secondary UTI (see UTI), or when severe uraemia results in uraemic encephalopathy."

Symptoms Associated With Overhydration


Fluid Retention/Build-Up

Sometimes a CKD cat may develop fluid retention or fluid build-up. This may be a sign of worsening kidney values or of heart problems, but in many cases it is actually  a sign of overhydration from either intravenous fluids (IV fluids) or subcutaneous fluids (sub-Qs).


Some vets believe it is impossible to overhydrate a cat through sub-Q fluids but unfortunately this is simply not true. Over the years, I've heard from quite a few people whose cats developed precisely this problem. In Renal Disease (2006) Polzin DJ Delaware Valley Academy of Veterinary Medicine, Dr Polzin states "Chronic subcutaneous fluid therapy can result in fluid overload in some patients, particularly when fluid volumes in excess of those recommended here are used. We have seen several cats given large quantities of fluid (200 to 400 ml/day) present with severe dyspnea due to pleural effusion. This condition can usually be avoided by reducing the volume of fluids administered."


A cat with fluid retention may:

  • exhibit loss of appetite, because the fluid may be pressing on the stomach causing a feeling of fullness.

  • find it uncomfortable to lie down on his or her side, or may sit up and refuse to lie down; this is because it is easier to breathe in this position.

  • appear to be gaining weight rapidly or suddenly (within the space of a few days)

  • be breathing faster (see Diagnosis for normal respiration rates)

  • start coughing

  • purr with a rattly noise

  • develop a nasal discharge

  • have runny eyes

  • have flaring nostrils

  • start breathing from the flanks (as if pushing every breath out)

If your cat feels "squishy" when you stroke him or her, this may indicate fluid retention caused by overhydration from excessive sub-Qs (although sometimes it merely means that air got into the line, in which case you need to work on your sub-Qs technique).


If you see any of these symptoms, you need to see a vet. If you see these symptoms while the vet is closed, it is probably OK to wait a few hours but monitor your cat closely (see Heart Problems for information on monitoring your cat's respiration rate) and of course do not give sub-Qs.


Unfortunately, you may not always see symptoms until the problem is severe. If your cat starts breathing with the mouth open, or has a limp and the limping leg is cold to the touch, this is a medical emergency indicating that your cat might be in congestive heart failure and you need to get to a vet as quickly as possible. In such a situation a chest x-ray is a good idea.


Do not give any sub-Q fluids if you see any of the symptoms above until you have had your cat checked by a vet. You should also never give a cat sub-Qs until the fluids from the previous session have been absorbed.


In many cases, you may find that invasive treatments are not necessary and that simply reducing the amount or frequency of sub-Qs solves the problem; so speak to your vet about this. Subcutaneous Fluids has information on amount and frequency of fluids.


Monitoring your cat's weight with baby scales is a good idea because sudden weight gain may alert you to this problem.


Cats who are on corticosteroids may also develop fluid retention.


Warning signs for congestive heart failure is a helpful site by an individual whose cat, Coco, had both CKD and heart problems, and gives useful information on what to watch for. Coco lived with CHF for quite some time.


Emergency resipratory assessment (2001) Hughes D Presentation to the World Small Animal Veterinary Association World Congress is rather technical but may still be of use.


Managing fluid and electrolyte disorders in renal failure (2008) Langston CL Veterinary Clinics Small Animal Practice 38 pp677-697 explains about the signs of overhydration.


Swelling in the Legs (Oedema), Abdomen (Ascites) or Feet

If overhydration is severe, fluid may collect:

  • in the lungs (pulmonary oedema)

  • around the lungs (pleural effusion)

  • in the abdomen (ascites). 

Your cat may appear swollen in the legs, face or abdomen. When Harpsie developed ascites (in his case, because of cancer), it felt like he had a hard little football in his abdomen. However, it is normal for cats to have a soft, squishy "pouch" of fluid after sub-Qs, which may move down into the front legs; this should gradually disappear as the fluids are absorbed.


Swelling may also be a sign of proteinuria. Alternatively it may be a sign of congestive heart failure.


Occasionally (rarely in cats), such swelling may be a sign of nephrotic syndrome. Nephrotic syndrome is not a disease in itself, but rather a collection of symptoms that may be seen as a result of glomerular disease. The primary symptoms of nephrotic syndrome include proteinuria, 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).


In very rare cases, a cat who develops puffy feet who is limping may have a condition called pillow paw or plasma cell pododermatitis. This is an autoimmune disorder more common in male cats which may need to be treated with steroids. Retrospective study of feline plasma cell pododermatitis based on histopathology submissions to a diagnostic laboratory (2017) Clinical/research abstracts accepted for presentation at ISFM World Feline Congress 2017 p967 mentions that it has been seen in cats with concurrent conditions that include glomerulonephritis Veterinary Partner has some information about this condition.


Pet Place has some information about pleural effusion


Pet MD discusses pulmonary oedema in cats.


Pet Place has some information about ascites.


Pet MD has information about ascites.


Weight Gain

Sometimes a CKD cat will suddenly gain a lot of weight in a short period of time, a matter of days or a week. This may indicate fluid retention, and needs to be investigated urgently, particularly if accompanied by fast heart rate, coughing, loss of appetite, breathing from the flank (as if pushing every breath out), limping, and particularly open-mouth breathing. If you see the last three symptoms, your cat's heart or lungs may be affected and you need to go to the vet immediately. Do not give any sub-Q fluids if you see any of the above symptoms or if your cat has gained a lot of weight suddenly or quickly until you have had your cat checked by a vet.


Sometimes a weight gain may seem small but we have to allow for the relatively small starting weight of a cat. So if, for example, a cat who weighs 8 lbs gains 1lb in a week, that is a weight gain of 12%. The human equivalent would be a 140lb person gaining almost 17 lbs in a week, which is clearly not possible in terms of true weight gain.


I recommend weighing your cat every day and monitoring trends. What is a reasonable weight gain? Be guided by your vet, but if your cat has just eaten or has been given fluids and has not yet urinated, then these will affect weight. 100ml of fluids weighs about 3.5 ounces (100g), for example, so if you weigh your cat immediately after giving fluids you might panic about a non-existent weight gain of 3.5 ounces. If you are trying to get weight onto your cat, an acceptable rate of actual weight gain should be determined by your vet, based on your cat's current weight and goal weight, but roughly speaking an increase of 2-3 ounces (50-75g) a week should be acceptable.



As with weight gain, coughing may be associated with fluid retention.


Nasal Discharge and/or Runny Eyes

This may indicate fluid retention, particularly overhydration with sub-Qs. Other causes of runny eyes include an upper respiratory tract infection or dental problems.


Urinary Issues


Proteinuria (Protein in the Urine)

Please visit the Proteinuria page for more information.


Urinary Tract Infections and Kidney Infections (Pyelonephritis)

Please see the Pyelonephritis and Urinary Tract Infections page.


Blood in Urine (Haematuria)

This may be a sign of a urinary tract infection, or bladder or kidney stones. It may also indicate high blood pressure.


Sometimes this is caused by cancer.


If your vet obtains a urine sample from your cat via cystocentesis (a needle into the bladder), this may sometimes cause blood in the urine.


Occasionally it may not be possible to ascertain the cause. There is a condition called "benign renal haematuria" which means there is bleeding from the kidneys but the cause cannot be found. However, this is rare in cats.


Persistent haematuria and proteinuria due to glomerular disease in related Abyssinian cats (2008) White JD, Norris JM, Bosward KL, Fleay R, Lauer C & Malik R Journal of Feline Medicine & Surgery 10(3) pp219-29 discusses how in Abyssinian cats with haematuria, the cause may be glomerular disease.


Severe or ongoing haematuria may cause or worsen anaemia, so you should always take your cat to the vet if you see this symptom.


See Diagnosis for detection litters which may detect blood in the urine.


Pet Place has some information about haematuria in cats.


Pet MD explains more about blood in urine.


Reduced Urination (Oliguria) or No Urination (Anuria)

If your cat is struggling to urinate, i.e. visiting the litter tray more frequently but producing little or no urine, the most likely cause is a urinary tract infection.


Other possible causes of reduced or no urination include acute kidney injury or kidney stones. If either of these is suspected, you need to see your vet urgently.


If your cat is urinating a lot because of diabetes and you get the diabetes under control, you may see a reduction in urination.


Certain antihistamines used as appetite stimulants such as cyproheptadine may cause reduced urination.


Alternatively, there is a very serious medical condition called a urinary tract blockage, which you can read about here. This is a medical emergency, but fortunately such blockages are relatively rare in CKD cats.


However, cats who are at the very end of their CKD journey may cease to be able to urinate because basically their kidneys have shut down. You can read more about this here, but be sure to rule out the causes outlined above before fearing the worst.



Incontinence means that your cat is unable to control when s/he urinates - s/he may urinate where s/he lies or walks, or perhaps urinate in his/her sleep. This may be caused by a urinary tract or kidney infection, or may be a symptom of uncontrolled diabetes. In my cat's case, it was a sign of a kidney infection.


Occasionally, it may be your cat is simply getting "caught short", particularly if you are giving subcutaneous fluids, and the litter tray is a long way away.


In some cases, it may indicate advanced renal damage.


Washington State University College of Veterinary Medicine has some information about incontinence.


Inappropriate Elimination

This is a polite way of saying your cat urinates (and/or defecates) outside the litter tray. This can be a sign of a urinary tract infection or constipation, and it may also be a symptom of uncontrolled diabetes; but sometimes it is a behavioural problem. 


In some cases in older cats, as mentioned in Geriatric cats and cognitive dysfunction syndrome (2008) Gunn-Moore DA Presentation to the 33rd World Small Animal Veterinary Association Congress, this can be a sign of cognitive dysfunction ( senility or "kitty Alzheimers").


Litter box aversion: is it medical or behavioral? (2012) is a blog entry by Pam Johnson-Bennett which aims to help you narrow down the possible cause, but I would still take your cat to the vet to rule out medical issues even if you think it is behavioural.


Litter box aversion Johnson-Bennett P is a series of articles on various aspects of this problem, including cats who pee on the bed.


Lying in the Litterbox

Cats may lie in the litterbox if they have a urinary tract infection or are constipated. This may also be a way to comfort themselves - many cats lie in their litter tray whilst hospitalised because it is the only thing that smells familiar to them, and has high sides so they feel more secure.


Occasionally, lying in the litter box is simply a sign of dominance Harpsie loved lying in the litter tray, thus controlling the other cats' access to it.


Treatment Options


It is possible to treat all of the above symptoms, in many cases effectively, and details can be found in the Treatments section.




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This page last updated: 13 November 2020

Links on this page last checked: 21 May 2020






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.



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