Quantitative renal scintigraphic determination of the glomerular filtration rate in cats with normal and abnormal kidney function, using 99mTc-diethylenetriaminepentaacetic acid

The nuclear imaging technique known as quantitative renal scintigraphy was validated as a means to assess the kidney function of cats. Renal function tests were performed in 6 healthy cats and 3 cats with clinical manifestations of kidney failure. In addition, the nephrotoxic drugs, gentamicin sulfate, or amphotericin B were used in an attempt to induce renal failure in 4 cats. Using linear regression analysis, equations were derived to estimate the glomerular filtration rate (GFR) on the basis of the renal percent uptake of 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA). One-way ANOVA and Student's t test were used to evaluate treatment effects on clearances of inulin and creatinine, percent uptake of 99-Tc-DTPA, and serum creatinine concentrations. The results show that the percent uptake of 99mTc-DTPA by the kidneys correlated well with the GFR obtained through the clearance of inulin. Thus, it was concluded that quantitative renal scintigraphy, using 99mTc-DTPA as a marker of kidney function, is an adequate technique to estimate the kidney function of healthy cats and cats with functional renal impairment. The best estimate of the GFR of cats, using the percentage dose of 99mTc-DTPA, was obtained on the 1- to 3-minute postinjection interval of the marker, using data that was background-subtracted, but not corrected for tissue absorption of gamma rays or binding of 99mTc-DTPA to plasma proteins. There was no significant difference in the mean inulin clearance, creatinine clearance, or percent uptake of 99mTc-DTPA between the 3 treatment groups of this study. Therefore, it was concluded that neither gentamicin nor amphotericin B are useful drugs in eliciting losses of feline kidney function that may be measurable through the procedures used in this study. Contrary to all other GFR studies in the cat, this study did not use any form of pharmacologic restraint. Therefore, the findings from this study are expected to reflect accurately the true GFR healthy nonanesthetized cats.