Feline lower urinary tract disease (FLUTD) is commonly seen in clinical practice. While the symptoms of FLUTD can result from a number of different causes, an increase in water intake is recognised to be beneficial regardless of the specific aetiology. In addition to the established approaches of increasing dietary fluid content and encouraging drinking of tap water, it has now been shown that offering supplements of nutrient-enriched water can effectively increase fluid intake and reduce urine osmolality in cats. These novel “water supplements” could provide an additional tool for veterinarians.
FLUTD: The clinical picture
The term FLUTD encompasses a range of conditions that affect the bladder and urethra. Most commonly, there is no identifiable cause for the symptoms, leading to a diagnosis of feline idiopathic cystitis (FIC). Other aetiologies include urolithiasis, bacterial infection, stricture, neoplasia and urethral plugs. In general, FIC is most common in cats under 10 years old, while bacterial infection and neoplasia account for a greater proportion of cases in older than younger cats (Bartges, 2002).
The optimal management of each case depends on the underlying cause. However, for all cats with FLUTD, it is generally advised to increase the water intake if possible.
The importance of encouraging water intake
Increasing fluid intake can have beneficial effects in FLUTD for several reasons. Firstly, increased hydration results in more dilute urine, reducing the irritation to the bladder lining by urine constituents such as potassium. Dilution of the urine also lowers the concentration of crystals, helping reduce the risk of urethral plugs forming in male cats. Given these benefits of diuresis, increased water intake has been linked to improved outcomes in FIC (Gunn-Moore and Shenoy, 2004) and a reduced risk of recurrence in cats treated medically for urethral obstruction (Eisenberg et al., 2013).
For cats susceptible to urolithiasis, dilution of solutes and crystals also helps to reduce the formation of stones. Additionally, a related benefit of increasing fluid intake in these patients is the encouragement of more frequent urination. This reduces the length of time that urine remains in the bladder, further decreasing the likelihood of stone formation. Increasing water intake is therefore recommended in all cases of FLUTD, and multiple approaches are used to achieve this. Voluntary drinking can be encouraged by optimising the number and nature of water bowls provided, and also by offering sources of moving water. Nutritional strategies include offering a wet rather than dry diet (Markwell et al., 1999) or increasing the sodium content of dry food to stimulate thirst (Hawthorne and Markwell, 2004). In addition to these well-established approaches, a new strategy is to use nutrient-enriched “water supplements”.
Increasing water intake using nutrient-enriched water
The principle is that nutrient-enriched water is more palatable than tap water, so cats offered a “water supplement” will voluntarily drink more throughout the day. This general approach is not new: some vets already advise owners to offer chicken or fish broth alongside tap water, and a 2012 study showed that cats demonstrated a clear preference for a liquid nutritional supplement over tap water (Verbrugghe et al., 2012).
Recent evidence shows that specifically formulated nutrient-enriched water supplements can indeed be effective. A 2018 study evaluating a low-calorie supplement consisting of electrolytes, glycerol and amino acids from animal digest and whey protein found that liquid consumption increased when cats were offered the supplement, and urine output in these cats was higher than in cats offered tap water alone (Zhangi et al., 2018). Improvement on various hydration indices was also seen, with lower urine specific gravity and osmolality, as well as lower urine creatinine, phosphate and urea nitrogen concentrations, in cats offered the supplement as opposed to those offered only tap water.
In light of this evidence, it is suggested that “water supplements” may provide an alternative way of increasing water ingestion, to be used alongside other strategies such as encouraging drinking and dietary modification. This new approach could prove useful in a range of situations where encouraging water intake is indicated.
Visit the Purina Institute for more information on the science of hydration.
Watch Dr Cecilia Villaverde Haro’s summary video for useful background on promoting water intake.
Interested in attending a live webinar in December to find out more about the science of hydration? Email firstname.lastname@example.org