Is a MAG-3 test conclusive of proper kidney function?

Q: My son is 18 months old. He has had urine infection 3-4 times in the last 3 months. He underwent VCUG, Renal Ultrasound and MAG-3 Lasix washout renal scan. Renal ultrasound shows that the right kidney measures 7.4 cm and left kidney is 6.03 cm in length. The left kidney showed significant hydrouretronephrosis and the diameter of the ureter measured at 1.7 cm in the flank. The left kidney has moderate amount of renal cortex measuring almost upto 1 cm in thickness. The VCUG didn't show any ureteric reflux. The MAG-3 Lasix renal scan shows 15% function from left kidney and 85% function from right kidney. The urologist has recommended the removal of the left kidney. Is there a way to improve the functioning of left kidney?

A:MAG-3 Renal scan is a standard test used to detect and evaluate hydronephrosis in the setting of obstruction of collecting system, determine the perfusion (blood flow) and the relative intrinsic function of each kidney. However, renal scan can help only predict the degree of differential function in each kidney with no information about the irreversibility of the lost function. Often due to some technical reasons, it is difficult to make an interpretation of the results. Moreover, the performance of it is highly operator dependent with results varying between various centres. Hence it is advisable to perform other tests including serum creatinine and urine tests to exactly characterise and estimate the kidney function. Finally, one would need to address the underlying anatomical defect in the urinary system of your child to see any significant improvement of the left kidney function.