Survey of dietary and medication practices of owners of cats with chronic kidney disease

Introduction

Chronic kidney disease (CKD) is a common systemic disease affecting cats. Clinical studies have demonstrated the importance of dietary management in slowing the progression of CKD in the cat.^1–3 Previous studies have indicated that the overall number of owners who are actively feeding veterinary diets ranges from only 12–21% of animals with various medical conditions.^4,5 However, specific data as to the prevalence of owners of cats with CKD feeding veterinary diets formulated for kidney disease are lacking in the literature.

Common clinical signs associated with CKD are decreased appetite, halitosis, dull hair coat, polyuria/polydipsia and weight loss.^6,7 There is a large variety of medications and dietary supplements recommended for treatment of CKD available commercially, but there is very little information as to the frequency of dietary supplement administration by owners of cats with CKD. In humans, the number of pills one takes (ie, pill burden) affects quality of life, as well as the likelihood of compliance with physician recommendations. ⁸ This may be an even more important issue in cats given the difficulty of medicating many cats and the option of euthanasia. In cats and dogs with heart disease, owners typically prefer quality of life to quantity of life.^9,10 Therefore, pill burden, with regard to both medications and dietary supplements, of the cat with CKD is an important question.

Finally, the issue of decreased or altered appetite in cats is another common and important consideration. While the role of anorexia in euthanasia of cats has not been reported, one study in dogs with congestive heart failure showed anorexia to be one of the most common clinical signs contributing to an owner’s decision for euthanasia. ¹¹ Information on these issues is important to gain a better understanding of how cat owners care for their cats with CKD and how to better communicate with owners. In addition, it would be useful information to be able to better design studies evaluating nutrition in cats with CKD. To answer these questions, the objective of this study was to describe the dietary and medication patterns of cats with CKD, as well as the prevalence of anorexia and concurrent diseases.

Materials and methods

A web-based survey was designed, with the assistance of the Tufts University Office for Institutional Research and Evaluation, consisting of 33 questions evaluating CKD, diet, use of supplements and medication history. The survey was advertised to owners of cats with CKD on online cat-owner support groups, social media (eg, Facebook, PetFinder, Craig’s List) and breeder websites. The survey was also advertised directly to veterinarians via email and published advertisements. The survey was posted online for 6 weeks for public participation. In order to participate in this survey, owners were required to be 18 years of age or older and own a cat with CKD. Owners with more than one cat could complete the survey more than once but each survey provided information on a single cat. No incentive was offered for participation in the survey, and all responses were anonymous. Owners were asked about their cat’s most recent creatinine value and, based on their reported values, IRIS stage was estimated. ¹² The majority of the questions were multiple choice or short-answer in design, although one of the questions on appetite was a visual analog scale. Short answers from the owners were evaluated and grouped according to the similarity of their contents. Each survey required 10–15 mins to complete. This study was approved by the Tufts University Institutional Review Board.

Results

Discussion

The majority of owners in this study were feeding a therapeutic diet formulated for kidney disease; however, it was frequently in combination with other commercial canned or dry diets or, less frequently, raw or home-cooked diets, so the therapeutic diet often only comprised a portion of the overall diet. Although veterinary therapeutic diets formulated for CKD have been associated with a longer survival time in some studies, these studies evaluated cats solely or primarily eating the veterinary therapeutic diet.^1–3 Veterinary therapeutic diets formulated specifically for CKD are likely to be less beneficial when fed only as a portion of the diet, particularly if the remainder of the diet has undesirable properties for a cat with CKD (eg, high phosphorus, raw-meat based diet, unbalanced home-cooked diet). ¹³ These results demonstrate the importance of obtaining a complete diet history at every visit for cats with CKD to determine what additional foods are being provided to the cat to ensure that the overall diet is optimized.^14,15

Anorexia (loss of appetite), hyporexia (reduced calorie intake) and alterations in food preferences were reported by 43% of owners of cats with CKD in the current study. Decreased appetite has been shown in multiple studies to be used by pet owners as an indication of quality of life for both cats and dogs.^9–11 This owner perception may be reflected in the current study by the large percentage (76%) of owners that either had food available to the cat all of the time or fed their cat three or more times per day, as well as the large variety of foods offered to many of the cats. Persistent alterations in appetite likely contribute to owners providing foods to their cat that are not ideal for the management of CKD, or are nutritionally unbalanced, in an attempt to encourage food consumption. Although not evaluated in the current study, the common finding of anorexia, hyporexia and alterations in food intake suggest that early use of feeding tubes may allow for better medical and nutritional management in the cat with CKD.

Dietary supplements were administered to 38% of the cats in this study. This figure is higher than that reported in previous studies of both healthy cats (10%) ⁵ and those with cardiac disease (13%). ¹⁶ This may reflect the true percentage of owners administering supplements to their cats with CKD or may be the result of bias of owners who chose to participate in the survey. Nonetheless, efficacy and safety of administration for most dietary supplements has not been established. Clinicians should enquire as to the administration of supplements as part of the complete diet history for every cat, as interactions between these products and medications may occur and can be difficult to diagnose in the chronically ill cat. Furthermore, the administration of some supplements may contribute to anorexia or hyporexia. Finally, the impact of these products upon the underlying disease in cats with CKD has not been evaluated. In one survey of humans diagnosed with CKD, 8% were unknowingly taking a supplement that could be harmful to the kidneys, many in the form of multi-vitamins that contained potentially harmful herbs. ¹⁷ Further studies are needed in cats with CKD in order to ensure that the administration of dietary supplements is not having adverse effects in cats with CKD.

Phosphorus is the nutrient that has been most consistently linked to the progression of CKD in cats.^18–20 As kidney disease progresses, dietary phosphorus restriction is no longer sufficient to maintain serum phosphorus concentrations in an acceptable range, and phosphate binders are required. Only 22% (225/1036) of owners in the current study reported that they administered phosphorus binders to their cat. While it is unknown how many of the cats in the current study had hyperphosphatemia, this would be useful information in future studies in order to determine the percentage of cats that have indications for receiving binders that actually are receiving them.

Concurrent diseases were common in the current study, with 40% of all cats having one or more concurrent diseases. The most common concurrent disease was hyperthyroidism, and this association has also been reported in a recent study. ²¹ Both CKD and hyperthyroidism are common in geriatric cats, and the treatment of hyperthyroidism can decrease the glomerular filtration rate and unmask underlying kidney disease. Heart disease was reported in 8% of the cats and was the second most commonly reported disease in this study, which is less than the reported prevalence rates of 10–15% in several studies of cats.^22,23 This may be the result of the fact that the prevalence in the current study is based on owner-reported presence of disease and some cats may have had occult heart disease that had not been identified if the cat had not undergone echocardiography. Similarly, the prevalence of hypertension in the current study was far below that of the 30% reported in a previous study. ²⁴ The prevalence of hypertension may be limited by the owners being unaware of blood pressure results, blood pressure measurements not being routinely performed in all practices, or a true lower prevalence when compared with the previous study.

Pill administration in any cat, but particularly in the hyporectic or anorectic cat, can be a challenge. The majority of owners in this study reported administering medications directly into their cat’s mouth, which is consistent with a recent study of owners of cats with hyperthyroidism. ²¹ However, the second most common method was mixing the pills with food, which may contribute to the high prevalence of decreased appetite reported by owners in this study as administering medications or supplements in the cat’s food can cause a food aversion in some cats. Many more owners in the current study reported directly pilling the cat compared with a previous study of cats with heart disease. ¹⁶ In that study, a larger percentage (34%) of cats were given pills in table foods. Clinicians should question owners as to the ease of medication administration and offer appropriate options if they are unable to pill the cat without food. Ensuring that the foods or treats used to administer pills are appropriate for CKD is also important in order to optimize the overall diet plan.

Limitations to this study include the intrinsic biases present in an owner-reported survey, such as the owners who chose to participate in the survey, the reliance on their reported information (eg, they may under- or over-report certain diseases), and the subjective state of the information reported (eg, creatinine, phosphorus or urinalysis results from owner recall rather than review of medical records). In addition, IRIS classification was based on owner-reported values so may not be accurate. This study is unique in the wide geographical distribution of owners of cats with CKD; however, no attempt was made to differentiate regional effects within these data. There may be regional effects within the USA on medical and nutritional practices, and also potential differences among different countries. Finally, only the behaviors reported by the cat owners responding to the survey could be assessed, and it is not possible to determine whether the owners’ practices deviated from recommendations by the veterinarian. The issue of adherence is an important one, and would be useful to address in future studies.

Conclusions

CKD remains one of the most commonly diagnosed diseases in the cat. Results of the current study demonstrate that there is wide variation in the medication and nutritional practices used in cats with CKD, with not all being optimal. A thorough dietary history, including the specific diet(s), treats, table food, supplements and medication administration, is an integral component to the management of the cat with CKD.^14,15 This information can aid the clinician in their communications with owners and also with researchers concerning design of future studies regarding the cat with CKD.