Evaluation of a single injection of 99mTc-labeled diethylenetriaminepentaacetic acid for measuring glomerular filtration rate in horses.

This study sought to evaluate a simpler method for measuring the Glomerular filtration rate (GFR) in horses. The researchers compared the GFR measurements obtained through traditional inulin clearance method with newer methods involving a single injection of a radioactive tracer (99mTc-DTPA) and found significant correlation between the inulin method and 99mTc-DTPA blood clearance.

Research Methodology

• The study involved 12 horses that were clinically normal. The GFR of these horses was measured using three methods, including the standard inulin clearance method and two methods involving a single injection of 99mTc-labeled diethylenetriaminepentaacetic acid (99mTc-DTPA).
• The first 99mTc-DTPA method used a two-compartment model to compute the GFR by observing the clearance of the tracer from the blood.
• The second 99mTc-DTPA method used digital gamma camera images of the kidneys to determine the buildup of the tracer in the kidneys, taken 0 to 10 minutes after the radionuclide was administered.

Research Findings

• The average GFR value obtained through the inulin clearance method was approximately 154.67 ml/min/100 kg of body weight.
• For the two-compartment 99mTc-DTPA method, the average GFR recorded was approximately 146.92 ml/min/100 kg.
• The GFR value obtained through the gamma camera method was approximately 154.7 ml/min/100 kg.
• The observations from the gamma camera method did not significantly align with the results from the inulin clearance method.
• However, there was a significant correlation (r=0.666, P less than 0.018) seen between the outcomes generated from the 99mTc-DTPA blood clearance method and the standard inulin clearance method.
• Through the 99mTc-DTPA gamma camera imaging, a significant difference was observed in the split function of the horse’s kidneys, with a greater GFR contribution from the right kidney.

Implications & Conclusion

• Considering the correlation observed between the inulin clearance method and the 99mTc-DTPA blood clearance method, it can be deduced that the latter might be a more practical choice for measuring GFR in horses.
• The added advantage of the 99mTc-DTPA blood clearance method is that it is less invasive as it doesn’t require urine collection.