Chronic Kidney Disease (CKD) is one of the most common diseases of older cats, with up to 80% of cats over age 15 affected in some studies. Up to 1 in 7 cats may die of this condition. While the disease is common, early signs are mild and non-specific and disease is often not detected until it is very progressed. While there are many published studies on CKD, large scale data on cats in primary care practice is lacking. The purpose of this study was to determine the prevalence and risk factors for CKD in cats presenting to primary care practices in the UK.
Records from a group of primary care veterinary practices across the UK were examined. 244 practices were included from Jan 2012 to Dec 2013. The study was designed as a frequency matched case control study with a concurrent retrospective cohort study. These studies examined the risk factors for CKD and survival following diagnosis respectively.
Records were reviewed using a series of keywords to look for diagnoses, tests, and treatments associated with CKD. A series of cats matching the search results were identified, of which 20% were randomly selected for detailed medical record review. These cats were classified as either incident (diagnosed during the study period) or pre-existing. The results of this detailed review were used to estimate total incidence and prevalence of disease. 353 448 cats were initially assayed, of which 11 863 were determined to be potential cases. 2368 were reviewed in detail, with 625 classified as incident and 336 as pre-existing. Demographic and historical data was also acquired, including but not limited to breed, date of birth, sex, neutering status, bodyweight, presenting complaints, IRIS stage, vaccine history, NSAID use, time since last anesthetic, and others.
Overall CKD prevalence was estimated at 1.2% (95% CI 1.1-1.3%) in cats under 9 years of age, and 3.6% (95% CI 3.3-3.9%) in cats 9 years or older. Burmese cats were the most likely breed to be diagnosed. 66% of cats were diagnosed with CKD after presenting to a vet due to clinical signs of CKD. Only 17.6% of cases were diagnosed due to geriatric or pre anesthetic testing. Weight loss and pu/pd were the most frequent clinical signs.
The most common treatment prescribed was a renal diet (63.2%). 22% of cats had no treatment prescribed, half of which were euthanized soon after diagnosis.
Factors associated with CKD in multivariate analysis included; hyperthyroidism, purebred status, lack of goitre, abnormal heart sounds, long term NSAID use, lack of HCM, no recent anesthesia, d a low bodyweight were predictive of CKD.
Of cats diagnosed with CKD, 60.8% died before the end of analysis in 2015. 37.9% of these were euthanized as a result of CKD, while another 22% cited general “quality of life” concerns. All-cause mortality was 8.1 deaths per 10 CKD cat-years at risk. Median survival time was 388 days, however there was a significant range of 88-1042 days. Factors associated with death included elevated serum phosphate at diagnosis, elevated UPC at diagnosis, breed, renal diet use, IV fluid therapy, diagnosis of constipation, bodyweight, phosphate binder use, and cystitis with survival.
Some of the risk factors (such as hyperthyroidism and NSAID use) have a logical correlation with the diagnosis of CKD. Others, however, appear to be conflicting (for example, lack of goiter and presence of hyperthyroidism). Similarly, many of the predictors of death and survival are as expected.
This study gives some valuable information as to the demographics and survival factors associated with CKD. While much of the information is not novel or surprising, it contains good data from a significant sample set. A potential limitation of this study is the confinement of data collection to the UK; which may have different environment and demographic distribution than North America. Further studies of this type (and ideally of a prospective nature) are warranted.
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