Kidneys and Liver in Cats

The kidneys and liver are among the most important organs in a cat's body – and also among the most vulnerable. Chronic kidney disease affects as many as 30–40% of cats over 10 years old and is the leading cause of death in older cats. Liver disease is the second most commonly diagnosed group of illnesses in cats overall. Even so, the right diet, targeted supplementation and regular preventive care can significantly slow their progression and support both the quality and length of your cat's life.

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A key fact that many owners don't realise is that both the kidneys and liver have an enormous functional reserve – clinical symptoms only appear in cats once more than 65–75% of the functional tissue has been damaged. This means the disease can progress unnoticed for a long time, and preventive support is worthwhile even in apparently healthy middle-aged and older cats.

Kidney support for cats

A cat's kidneys are exceptionally efficient organs – cats are evolutionarily adapted to life in dry environments, and their kidneys can produce remarkably concentrated urine. This ability comes at a price, however – a cat's kidneys are under heavy strain throughout its life, and gradual wear and tear is practically inevitable in older cats.

Chronic kidney disease (CKD) in cats is a progressive condition that cannot be cured, but its course can be significantly slowed. Controlled phosphorus intake plays a key role – phosphorus accelerates damage to kidney tissue, and restricting it is one of the most important dietary measures for cats with kidney disease. Special products called phosphate binders are given with food and reduce the absorption of phosphorus from the diet.

Key supplements for supporting a cat's kidneys:

• Phosphate binders – bind phosphorus from food in the gut and prevent it from being absorbed into the bloodstream. They are one of the most important products for cats diagnosed with CKD. They should only be given under veterinary supervision, as excessive phosphorus restriction can be harmful.
• Omega-3 fatty acids (EPA and DHA) – reduce inflammation in kidney tissue, slow the progression of CKD and improve blood flow to the kidneys. Fish oil is one of the most recommended supplements for cats with kidney disease – always choose products formulated for animals with a controlled EPA and DHA content.
• Antioxidants – vitamin E and C – protect kidney cells from oxidative damage caused by chronic inflammation. Oxidative stress plays a key role in CKD progression, and reducing it slows the loss of functional tissue.
• B vitamins – cats with kidney disease lose increased amounts of B-group vitamins through urine, as damaged kidneys reabsorb them less efficiently. Supplementing with B-group vitamins – particularly B1, B6 and B12 – is very important for cats with CKD.
• Probiotics and intestinal sorbents – special probiotics and products such as activated charcoal or zeolites reduce the level of nitrogenous waste products in the blood by promoting their excretion through the gut instead of the kidneys. This reduces the burden on damaged kidneys and eases the symptoms of uraemia.
• Potassium – cats with CKD often suffer from hypokalaemia – a potassium deficiency caused by increased losses through damaged kidneys. Low potassium causes muscle weakness and pain, and worsens kidney function. Potassium supplementation is very important for these cats, but always under veterinary supervision.

Liver support for cats

The liver is the most complex metabolic organ in a cat's body – it handles over 500 different functions, from detoxifying harmful substances and metabolising nutrients to producing blood proteins and bile. A cat's liver is particularly vulnerable, as cats have a limited ability to metabolise certain substances that are perfectly safe for other species. This is why many medicines, plants and chemicals that are harmless to dogs or humans are toxic to cats.

The most common liver diseases in cats are hepatic lipidosis (fatty liver disease caused by starvation), cholangitis (inflammation of the bile ducts) and IBD (inflammatory bowel disease) – which very often occurs alongside liver disease in cats as so-called triaditis.

Key supplements for supporting a cat's liver:

• SAMe (S-adenosylmethionine) – a naturally occurring substance that is essential for the liver's detoxification function and for producing glutathione – the most important antioxidant in liver cells. Cats with liver disease have a reduced ability to synthesise SAMe, and supplementing it is one of the most recommended treatments in hepatoprotective therapy for cats.
• Milk thistle (Silymarin) – the best-known natural hepatoprotective herb. Silymarin protects liver cells from toxin damage, supports their regeneration and has strong anti-inflammatory effects. It is safe for long-term use and combines well with SAMe.
• Glutathione – the main antioxidant in liver cells, which neutralises toxic substances and protects cells from oxidative damage. Its levels are significantly reduced in cats with liver disease. Direct supplementation with glutathione or its precursors supports the liver's detoxification capacity.
• Taurine – an essential amino acid for cats, necessary for producing bile acids and for proper liver function. Taurine deficiency contributes to the development of liver disease, and supplementation is particularly advisable when feeding a home-prepared diet or lower-quality food.
• Vitamin B12 (cobalamin) – cats with liver or intestinal disease very often have a vitamin B12 deficiency, which worsens both liver function and overall condition. B12 supplementation is almost always indicated in these cats and significantly improves their overall condition and appetite.
• Omega-3 fatty acids – reduce liver inflammation, help with hepatic steatosis and support proper fat metabolism in the liver. Particularly suitable for cats with hepatic lipidosis or chronic liver inflammation.

Warning signs to watch out for

Cats are experts at hiding signs of illness. Early warning signs of kidney or liver disease that you shouldn't overlook include:

• Increased thirst and frequent urination – one of the earliest signs of CKD. Damaged kidneys can no longer concentrate urine, so the cat has to produce more of it.
• Weight loss and loss of muscle mass – both kidney and liver disease cause gradual weight loss even when appetite is maintained.
• Yellowing of the skin, gums or whites of the eyes – jaundice is a sign of liver disease or haemolytic anaemia requiring immediate veterinary attention.
• Vomiting and loss of appetite – chronic vomiting or refusing food in a middle-aged or older cat always calls for a veterinary check-up.
• Lethargy and reduced activity – a cat that stops jumping or playing, or spends an unusually long time hiding, may be signalling a chronic illness.
• Breath that smells of ammonia or overheated fat – a distinctive odour caused by the build-up of waste products in the blood when the kidneys or liver are failing.

Practical tips for looking after your cat's kidneys and liver:

• Always make sure your cat has access to fresh water – adequate hydration is the most important way to prevent kidney disease. A drinking fountain with running water significantly increases fluid intake.
• Never give cats medicines intended for humans or dogs without consulting a vet – paracetamol, ibuprofen and aspirin are all fatally toxic to cats.
• Have regular blood tests done at least once a year in middle-aged and older cats – this can detect kidney and liver damage long before clinical symptoms appear.
• Always consult a vet about supplements to support the kidneys and liver – phosphate binders, potassium and SAMe in particular require correct dosing based on the cat's current condition.
• Never let a cat go without food if it has been diagnosed with kidney or liver disease – even a short period without eating can trigger hepatic lipidosis in these cats and significantly worsen their condition.

The kidneys and liver work quietly for your cat every day, unnoticed – until they need help. Regular preventive care, the right diet and timely supplementation are the simplest way to lighten their load and help your cat enjoy a longer, happier, more active life.