Assessments of Factors that Affect Glomerular Filtration Rate and Indirect Markers of Renal Function in Dogs and Cats

Abstract

ABSTRACT. Chronic kidney disease is one of the most common disorders in dogs and cats. The plasma urea nitrogen (P-UN) and creatinine (P-Cre) concentrations are not sufficiently sensitive for early diagnosis of renal dysfunction. Although urine and plasma clearance methods allow earlier detection of reductions in the GFR, it is difficult to estimate a mildly reduced GFR from the values obtained by these methods, as they are also affected by physiological factors, such as body weight (BW) and age. The present study is a retrospective survey designed to assess the factors that affect markers of kidney function and to revaluate the clinical utility of the markers, including P-UN, P-Cre and GFR determined by plasma iohexol clearance (PCio) in dogs and cats. The P-UN, P-Cre and PCio values in dogs and the P-Cre and PCio values in cats were significantly correlated with BW (P<0.001). PCio in smaller dogs (15.0 kg) was significantly and inversely correlated with age. In smaller dogs, increase of P-UN alone might warrant a suspicion of a decreased GFR, but in contrast, P-Cre may be inefficient for detecting renal dysfunction or determining the severity of CKD compared with that in larger dogs ( 15.1 kg). P-Cre in larger dogs correlated better with PCio than in smaller dogs, suggesting that P-Cre in larger dogs was a more sensitive marker of reduced GFR.KEY WORDS: body weight, plasma creatinine, plasma iohexol clearance, plasma urea nitrogen.J. Vet. Med. Sci. 72(9): 1129-1136, 2010 Chronic kidney disease (CKD) is one of the most common disorders and is a common cause of death in dogs and cats. The prevalence of renal diseases has been reported to range from 0.5 to 7% in dogs and from 1.6 to 20% in cats [29,43]. Although CKD occurs in dogs and cats of all ages, the mortality of CKD commonly increases with age. In human and veterinary medicine, CKD is diagnosed by detecting chronic decreases in the glomerular filtration rate (GFR) or the presence of chronic renal damage [4,36]. GFR can be evaluated indirectly from the concentrations of plasma and urine markers, which are dependent on the amount eliminated by the kidneys. The plasma urea nitrogen (P-UN) and creatinine (P-Cre) concentrations are widely used as endogenous markers to evaluate renal function in dogs and cats because they can be easily, rapidly and cheaply measured. GFR is measured directly by urine or plasma clearance methods using inulin, creatinine or iohexol [7,14,15,20,21,33,34]. Although the urinary clearances of inulin and creatinine are considered to be the gold standards for measuring GFR in humans and animals, these methods are impractical in clinical settings because they require insertion of a bladder catheter, which is associated with a risk of developing a urinary tract infection or urethral injury; complete collection of a timed urine sample; and continuous infusion of the marker. The single injection technique can be used to determine plasma clearance from the elimination curve of a marker in plasma after a bolus injection. Plasma clearance ca...

Comparison of Serum Concentrations of Symmetric Dimethylarginine and Creatinine as Kidney Function Biomarkers in Cats with Chronic Kidney Disease

“…It does, however, only correctly identify 17% of all cases (sensitivity). This is consistent with the conclusion of others that plasma Cr is not sufficiently sensitive for early diagnosis of renal dysfunction in cats . As a screening test, a negative result is poor at reassuring the owner that the patient does not have CKD (NPV = 70%), although at the initial screening the test correctly identifies 100% of those that do not have CKD (specificity).…”

Relationship between Serum Symmetric Dimethylarginine Concentration and Glomerular Filtration Rate in Cats

“…This finding, taken in combination with the correlation between SDMA and creatinine, underscores the need to examine a larger number of cats across the full range of GFRs to fully evaluate the relationship between SDMA and GFR. Given the known limitations of creatinine, particularly its sensitivity to muscle mass and body composition, more reliable markers of renal function in cats would greatly facilitate early and accurate diagnosis of CKD. Future studies are needed in order to identify clinical factors that might influence the relationship between GFR and SDMA and to assess the potential utility of SDMA in diagnosing CKD in cats.…”

“…Measurements of plasma creatinine concentrations are commonly used to assist veterinarians in the diagnosis of CKD in cats, and plasma creatinine concentrations increase when GFR reduces . However, plasma creatinine concentration is impacted by a number of extrarenal factors such as muscle mass that can confound accurate diagnosis, and significant kidney function has already been lost by the time creatinine concentrations are outside of the reference range for normal cats . Urine specific gravity can be helpful in assessing kidney function, but urine samples are often not collected in routine clinical practice despite their diagnostic utility.…”

Testes de avaliação de injúria renal precoce em cães e gatos

“…Esse método ainda não foi relatado em gatos (KERL;COOK, 2005). Embora as determinações das taxas de depuração de creatinina e inulina sejam consideradas os melhores métodos para a avaliação da TFG em animais e em humanos, esses métodos são de difícil execução em situações clínicas devido à necessidade de manutenção de um cateter urinário, o qual está associado ao risco de infecções do trato urinário ou lesões uretrais, colheita completa de toda a amostra de urina produzida e infusão contínua de um marcador (MIYAMOTO, 2001a;MIYAGAWA;TAKEMURA;HIROSE, 2010).…”

“…Embora a doença renal crônica ocorra em animais de todas as idades, a taxa de mortalidade usualmente aumenta com o aumento da idade (MIYAGAWA; TAKEMURA; HIROSE, 2010). A doença renal crônica é comumente diagnosticada em gatos geriátricos (LULICH et al, 1992).…”