ABSTRACT: Chronic kidney disease (CKD) is one of the most common diagnoses made in clinical practice. In recent years, there have been many advances in treatment options and long-term home care can be very rewarding for all involved. Treatment aims to help the patient to compensate for their renal disease allowing them to live for as long as possible with as good a quality of life as possible. The most proven treatment is feeding a prescription renal diet but there are many other measures that can be helpful to individual patients.

Kidneys perform many complex functions and, therefore, a range of complications can be seen in patients with CKD (Table 1). Treatment should be focussed on:

•   identifying and treating any underlying cause of the disease, such as bacterial pyelonephritis

•   ‘proven’ general therapies for CKD, such as prescribing renal diets and ensuring that the cat maintains normal hydration, as far as possible

•   additional treatments according to the individual’s specific needs.

Prescription renal diets

Prescription renal diets are the single most beneficial proven treatment for cats with renal disease. Several studies have now shown, emphatically, that cats with renal failure that will eat these diets will live much longer, healthier lives. The diet should be introduced gradually to encourage acceptance by the cat and all efforts should be concentrated on persuading the cat to eat the food – even if it takes months to achieve this aim!

Maintaining normal hydration status

Dehydration is associated with reduced renal perfusion, which causes a worsening in renal function. Acutely decompensated cats require intravenous fluid therapy, but maintaining adequate fluid intake at home is of prime importance. Cats with CKD should be encouraged to drink as much as possible through tactics that include feeding moist rather than dry foods, adding water to the food, using water fountains and offering flavoured water (prawns liquidised in water, for example).

With cats that fail to maintain adequate voluntary fluid intake, some owners may be willing to administer subcutaneous fluids at home (Figure 1). Subcutaneous fluid therapy is indicated in those cats suffering from recurrent episodes of dehydration. The sole aim of this therapy is to maintain normal hydration status and prevent dehydration.

Figure 1: Home subcutaneous fluid therapy is helpful in maintaining hydration in those cats vulnerable to dehydration

Managing hyperphosphataemia

Hyperphosphataemia is present in around two thirds of CKD cats and is a major trigger for the development of renal secondary hyperparathyroidism (R2HP). R2HP is a cause of clinical signs of CKD and also contributes to the progression of the disease.

Renal prescription diets and/ or phosphate binders – such as Renalzin and Ipakitine –   are recommended in cats with CKD. Phosphate restriction is believed to be a key reason why cats eating renal diets live so much longer. In cats that won’t eat a renal diet, phosphate binders are especially important to help treat/prevent hyperphosphataemia.

Oral phosphate binders should be mixed with the food – they work by binding to phosphate present in the diet, retaining this in the bowel and hence limiting the amount of phosphate that can be absorbed by the body. It may take several months for the total body excess phosphate levels and hence blood phosphate levels to normalise.

The International Renal Interest Society (IRIS) has devised guidelines for treatment of cats with CKD and recommends that blood phosphate levels are kept at the bottom of the reference range (1 – 1.2 mmol/l) as far as possible.

Managing poor appetite, nausea and vomiting

Many cats with CKD suffer from uraemic gastritis, contributing significantly to their inappetence and weight loss. General nursing techniques, such as feeding warm food by hand, may help (Figure 2). In other cases, it is worth trying antacids (H2-antagonists, such as famotidine) anti-emetics and/or appetite stimulants (cyproheptadine, mirtazipine).

Figure 2: Hand feeding and general nursing tactics can help to encourage acceptance of renal prescription diets

In those cats that are bright and relatively well but where appetite remains poor, one long-term possibility includes placing a feeding tube such as an oesophagostomy or gastrostomy tube.

Managing hypokalaemia

Hypokalaemia (potassium < 4 mmol/l), caused by inappropriate loss of potassium in the urine and inadequate intake owing to inappetence, is present in around 25 percent of cats with CKD. The cardinal sign of severe hypokalaemia is polymyopathy, with generalised muscle weakness and ventroflexion of the neck (Figure 3). However, more mildly affected cats will only suffer from non-specific signs, such as lethargy, weakness and loss of appetite.

Figure 3: Severe hypokalaemia is associated with muscle weakness. One manifestation is ventroflexion of the neck, illustrated here

Hypokalaemia is not only a cause of clinical signs but it also adversely affects renal function. Potassium gluconate is the preferred oral supplement as it is the least gastric irritant. Renal diets which are supplemented with potassium – but that are also non-acidifying and low in protein –   help to maintain normal serum potassium concentrations.

Managing systemic hypertension

Systemic hypertension affects at least one in five CKD patients. It can have serious consequences including blindness, neurological signs (such as seizures), cardiac changes (most commonly, a systolic heart murmur resulting from cardiac remodelling) and renal damage.

Blood pressure should be evaluated as a routine part of all check-ups of CKD cats and anti-hypertensive therapy prescribed to those where the mean systolic blood pressure readings, taken with the cat in a calm state, are persistently above 170 mmHg, or where there is evidence of hypertensive retinopathy. Ocular manifestations of systemic hypertension include retinal oedema, haemorrhage and detachment.

The most commonly used drugs for treatment of feline hypertension are the calcium channel blocker, amlodipine besylate and the ACE inhibitor, benazepril. In general, amlodipine
is more effective in lowering blood pressure than the ACE inhibitors. In some cats, a combination of these drugs may be required to achieve adequate control.

Managing proteinuria

Proteinuria is common in cats with CKD and is associated with a worse prognosis. ACE inhibitors, such as benazepril, are indicated in cats with a urine protein : creatinine ratio persistently greater than 0.4, where pre- and post-renal causes of proteinuria have been excluded.

ACE inhibitors should only be used in clinically stable, normally hydrated cats.

Managing urinary tract infections

Around 25 per cent of cats with CKD suffer from a bacterial cystitis at some point in the course of their disease – probably since the urine they are producing is so dilute. Bacterial cystitis may pose a risk of ascending infection and pyelonephritis or may represent bacterial seeding of the urine from pre-existing pyelonephritis.

Unfortunately, in many cases the bacterial infection does not cause any clinical signs of cystitis – in other words, the infection is clinically ‘silent’. A course of antibiotics, ideally chosen on the basis of bacterial culture and sensitivity results, is often needed for several weeks or months in order to successfully eliminate the bacterial infection.

Managing metabolic acidosis

Metabolic acidosis is commonly encountered in patients with CKD and may contribute to a number of clinical signs including anorexia, vomiting and weight loss. Feeding a renal diet helps to reduce the incidence of acidosis, although a small number of cats may require further treatment with oral sodium bicarbonate.

If the cat is receiving a urinary acidifying diet, this should be stopped and, ideally, a low-protein diet instituted.

Managing anaemia

Progressive anaemia is common in CKD and can contribute to lethargy, inappetence, weakness and weight loss. In some cats, iron deficiency can contribute to the anaemia both through inadequate dietary intake and gastro-intestinal blood loss (Figure 4). Treatment options which may be considered include iron supplementation, anabolic steroids and recombinant human erythropoietin.

Figure 4: Pallor can be an indication of anaemia – a complication seen in around 35% of cats with CKD

Check-ups

Monitoring visits are very important to ensure that owners are supported and that clinical problems are identified and treated promptly. The required frequency of check-ups varies according to the patient’s needs, but should initially be at least once a month. All check-ups should include weighing the patient and assessing for clinical problems, such as dehydration.

Blood pressure and laboratory monitoring should be checked according to the patient’s needs and owner’s concerns – I measure blood pressure every three to six months and reassess blood and urine tests every six to 12 months, depending on the individual patient’s needs.

The long-term outlook for cats with CKD is very variable ranging from a few weeks post diagnosis to many years.

For many cats, once stabilised, their care is not difficult, time-consuming or stressful and it is possible to provide a good quality of life for months or years. 

Author

Sarah M A Caney

BVSc PhD DSAM(Feline) MRCVS

Sarah is a 1993 graduate of the University of Bristol. She is an RCVS Specialist in Feline Medicine and loves both first opinion and referral feline medicine. In 2007, she founded Cat Professional, which aims to provide cat owners and veterinary professionals with the highest quality information, advice, training and consultancy services.

The Cat Professional has published three books Caring for a Cat with Kidney Failure, Caring for a Blind Cat and Caring for a Cat with Lower Urinary Tract Disease which are all available as 'soft backs' and electronic books via her website

Useful resources

Caring for a cat with kidney failure by Dr Sarah

Caney. Available through www.catprofessional.com

and a variety of online bookstores

Free downloads are available on the Cat Professional website

http://www.catprofessional.com/free_downloads.html on a number of relevant topics including:

•   potassium supplementation

•   pyelonephritis

•   Doppler blood pressure measurement

•   ocular manifestations of systemic hypertensior

•   giving subcutaneous fluids

•   encouraging your cat to take in more fluids www.iris-kidney.com for guidelines and information from the International Renal Interest Society (IRIS) http://www.fabcats.org/kidney.html http://www.felinecrf.com/

Disclaimer

Some treatments mentioned in this article are not licensed in the UK. All medication should be used according to the cascade recommendations http://www.noahcompendium.co.uk/Compendium/Overview/-45043.html

Veterinary Nursing Journal • VOL 25 • No9 • September 2010 •