Pathogenesis and treatment of feline lower urinary tract disease

Transcription

1 Vet Times The website for the veterinary profession Pathogenesis and treatment of feline lower urinary tract disease Author : Sarah Caney Categories : RVNs Date : May 1, 2011 Sarah Caney BVSc, PhD, DSAM (Feline), discusses triggers of urinary tract disease in cats and how these underlying causes may be prevented and appropriate treatment started Summary FELINE lower urinary tract disease (FLUTD) is a common diagnosis made in practice, with between one and 10 per cent of all cats suffering from this problem. Inactive, overweight, neutered, indoor-only cats and those from multi-cat households are at increased risk. Signs of lower urinary tract disease are often very distressing for both cat and owner, with a large number of these cases presenting out of hours. The majority of cases, especially in cats under the age of 10 years, are due to idiopathic cystitis (FIC), but other differentials include urolithiasis, bacterial infections and urethral plugs. In cats more than 10 years of age, bacterial urinary tract infections are responsible for almost half of the cases. An accurate diagnosis is required to facilitate the most appropriate treatment plan. Treatment of the underlying cause, where possible, is preferred. In the case of FIC, addressing potential sources of stress to the cat and encouraging production of less-concentrated urine are key to success. Other medical treatments may be needed in some patients. Key words FLUTD, cystitis, FIC, bladder, urolithiasis FELINE lower urinary tract disease (FLUTD) is a term used to encompass a number of 1 / 6

2 conditions that affect the bladder and urethra, and that may be associated with inappropriate urination. FLUTD is most common in young and middle-aged cats. There are several important medical causes of the condition, but idiopathic FLUTD also known as feline idiopathic cystitis (FIC) is the most common by far. Other causes include urolithiasis, infections, plugs, tumours and polyps. Feline idiopathic cystitis FIC is especially common in young and middle-aged cats, when it accounts for more than 50 per cent of FLUTD cases (Bartges, 2002). FIC can be obstructive or non-obstructive. Male cats are most vulnerable to obstructive disease and this condition needs emergency treatment. Clinical signs with non-obstructive FIC are often self-limiting usually within five to 10 days. However, most affected cats suffer from repeat episodes of clinical signs, which can be very distressing for both cat and owner. In general, the frequency and severity of these episodes gradually decreases over time. Stress is now known to play a very important role in triggering and/or exacerbating FIC. The causes of chronic stress suggested to be most damaging are those over which the cat has little or no control (Cameron et al, 2004). Urolithiasis Urolithiasis is the medical term for stones that are most commonly located in the bladder. Small stones can be passed in the urine, but larger ones can block the urethra, causing potentially lifethreatening obstruction. Uroliths are the cause of FLUTD in around 20 per cent of cats under 10 years of age and in around 10 per cent of cats older than 10 years (Bartges, 2002). Uroliths can cause inflammation through irritating the lining of the bladder. There are several different types of bladder stones from which cats can suffer common examples include struvite and oxalate. It is important to remember that stones are not the same as crystals. Stones are visible to the naked eye and vary in appearance according to their make up. Struvite stones tend to be very smooth and pebble-like in appearance. Oxalate stones are often very spiky and rough. Crystals cannot be seen by the naked eye and are only visible by looking at a sample through a microscope, unless there are large numbers of crystals, in which case a sandy or gritty appearance might be seen in a urine sample. Crystalluria presence of crystals in the urine is not damaging to an animal s health and does not cause FLUTD. Most cats eating a dry diet will have crystals in their urine and this is normal (Sturgess et al, 2001). Crystals can be a cause of concern in the following situations: 2 / 6

3 presence of urate crystals these may indicate that the cat has a liver problem; when large numbers of crystals are seen (to the extent they are visible to the naked eye), this may indicate an increased risk of obstruction; and in a cat with urolithiasis the type of crystal may indicate the type of stone present (although this is not always true). Urethral plugs Urethral plugs account for about 20 per cent of FLUTD cases in cats under 10 years of age. Plugs are less common in older cats, accounting for around six per cent of FLUTD cases in cats over the age of 10 years (Bartges, 2002). Urethral plugs are a potential cause of urethral obstruction. These plugs are made up of a protein matrix and some crystals (usually struvite). This matrix is formed from protein that has leaked through the bladder wall as a result of inflammation of the bladder lining. Urethral plugs are often associated with FIC and many clinicians believe they form a subset of FIC making FIC responsible for around 75 per cent of cases of FLUTD in cats under 10 years of age. Rarely, urethral plugs can occur as a result of bladder stones, tumours or infections. The protein matrix can also cause a urethral obstruction even when no crystals are present. However, when crystals are present, these can become trapped in the matrix and make it more likely to cause an obstruction. Obstruction can be caused by the plug itself, but also by urethral spasm associated with the pain caused by the presence of a plug. Bacterial infections Bacterial infection is a rare cause of FLUTD, accounting for less than two per cent of cases in cats less than 10 years of age. However, in older cats, bacterial infections are much more common, accounting for around 45 per cent of cases (Bartges, 2002). This is thought to be the case since: older cats often have more dilute urine, which is easier for bacteria to grow in; and older cats often have other illnesses that predispose them to infections for a variety of reasons. Common illnesses include diabetes mellitus, hyperthyroidism and chronic kidney disease. The most common bacterial infections are Escherichia coli (responsible for 40 to 70 per cent of cases), Enterococcus species (responsible for 25 to 30 per cent of cases) and Staphylococcus species (responsible for up to 20 per cent of cases). Cats suffering from bacterial urinary tract infections (UTIs) are vulnerable to repeated infections and for the infection to ascend to the kidneys causing pyelonephritis. 3 / 6

4 Other causes of FLUTD Other, less common, causes of FLUTD include bladder tumours, trauma and congenital causes of incontinence. Diagnosis of FLUTD depends on: taking an accurate behavioural and medical history to obtain as many clues possible as to the cause of the problem; performing a physical examination to help identify causes of FLUTD for example, a bladder tumour may be palpable in some cases; urinalysis to look for evidence of haematuria, bacterial urinary tract infection and other abnormalities. In general, cystocentesis is the preferred method for urine collection; haematology and serum biochemistry to look for relevant underlying systemic disease for example, renal disease or diabetes mellitus, and more serious abnormalities that might occur in a blocked cat such as dehydration, hypocalcaemia and hyperkalaemia; and diagnostic imaging (radiography, ultrasonography) to look for stones in the bladder and/or urethra, tumours and other problems. FLUTD treatment Optimal treatment of FLUTD depends on making an accurate diagnosis of its origin for example, bacterial urinary tract infections should be treated with an appropriate antibiotic, as identified on culture and sensitivity testing. Since non-obstructive FIC is the most common cause of FLUTD, the remainder of this article will concentrate on current treatment recommendations for this condition. Although non-obstructive FIC is considered to be self-limiting, treatment is usually recommended since it can be a painful and debilitating condition. All current medical treatments for FIC are palliative aiming to support the cat through an episode and reduce the risk of further episodes. The biggest long-term improvements are seen using a dual approach to reduce stress and encourage the cat to produce more dilute urine (Buffington et al, 2006). Reducing stress in the home Efforts should focus on identifying and addressing potential causes of stress in the home. These may include conflict between the FIC cat and other cats in the home or neighbourhood, addition of 4 / 6

5 new pets or people into the home, sudden changes of routine and so on. FIC is very common in households where there are large numbers of cats. In severe cases, referral to a veterinary behavioural expert may be valuable to accurately diagnose and resolve causes of chronic stress. Synthetic F3 feline facial pheromone preparations, such as Feliway (Ceva Animal Health), may also help to reduce tension sometimes found in multi-cat households. These can act as a confirmatory signal that the environment is safe and, therefore, must be used in conjunction with other environmental management strategies, such as ensuring adequate litter boxes are provided, and so on. Environmental enrichment is beneficial as a means of reducing stress. Examples of positive ways of improving a cat s environment include climbing frames with resting areas, and playing games that stimulate natural cat behaviour. Restricting (or reducing) the number of cats in the home to socially compatible levels, and resisting the temptation to expand the household by introducing new cats, will help to reduce the incidence of stress-related conditions such as FIC. Urine concentration The cat will be less likely to suffer from episodes of FIC if it produces more dilute urine. The aim is for the cat to be producing urine with a specific gravity of around This encourages frequent urination and dilutes any irritant components of the urine. Producing more dilute urine does not treat the underlying cause of FIC, so issues such as stress also need to be addressed. There are many strategies that can be used to encourage water intake a comprehensive guide can be found in the free download section of Other treatments A number of medical treatments may be suggested in cats with FIC. These include treatments for urethral spasm, such as prazosin and dantrolene; and painkillers that can be useful in acute episodes. The best outcome for a cat with FLUTD requires attention to all the factors discussed above. Cat Professional is running a survey assessing the usefulness of Zylkène in cats with FIC. For more information visit References and further reading Bartges J W (2002). What s New in Feline LUTD? Proceedings of ECVIM. Buffington C A T, Westropp J L, Chew D J and Bolus R R (2006). Clinical evaluation of 5 / 6

6 Powered by TCPDF ( multimodal environmental modification (MEMO) in the management of cats with idiopathic cystitis, JFMS (8): Cameron M E, Casey R A, Bradshaw J W S, Waran N K and Gunn-Moore D A (2004). A study of the environmental and behavioural factors that may be associated with feline idiopathic cystitis, JSAP (45): Gunn-Moore D A and Cameron M E (2004). A pilot study using synthetic feline facial pheromone for the management of feline idiopathic cystitis, JFMS (6): Sturgess C P, Hesford A, Owen H and Privett R (2001). An investigation into the effects of storage on the diagnosis of crystalluria in cats, JFMS (3): / 6