Q: My 6 years old daughter was diagnosed with Wilms Tumour last year. She had her right kidney removed, and now only has one kidney. I am concerned about her health in the long run with a single kidney. She went through chemotherapy and sees the oncologist monthly. Her creatinine level is 0.6, and I was reading about the GFR. Hers seems to be about 107 ml/min according to the Schwartz formula but at 84 ml/min on the Counahan-Barratt formula. She gets frequent headaches and stomach aches and I am concerned. Should she see a paediatric nephrologist? She has a kidney belt and plays soccer but I wonder if I should send her to school?

A:Schwartz and Counahan-Barratt formulae are among the most commonly used predictive equations for estimating Glomerular Filtration Rate (GFR) in children and are convenient and practical to use by physicians. Both formulas use height in the estimate. However, because of some inherent differences between the two (likely related to the different assays used to measure creatinine at the time when these formulae were derived), one may come across differences in their estimates of GFR. More importantly, it is the change in the height (which gets impacted by the muscle mass) and the serum creatinine value that would impact the GFR estimate by either formula. Hence, as long as the serum creatinine is stable and within the normal range as in the above case, there is no need for any intervention. The long-term prognosis with a single kidney are excellent with the sole kidney taking up the function of the other kidney by simply growing bigger over the time. Studies of children with the removal of the affected kidney (unilateral nephrectomy) for Wilms tumour have shown good preservation of the other unaffected kidney. However, chemotherapy or radiotherapy offered during the course of follow-up treatment of Wilms tumour could potentially affect the sole kidney, which would necessitate continued follow-up of the kidney function by checking the serum creatinine. This could be done under the supervision of her oncologist with the close surveillance on the recurrence/relapse of the tumour. She should certainly be encouraged to undertake routine active outdoor activity including attending school as permitted by her oncologist. It may help to see a pediatric nephrologist as part of an initial follow up to the Wilm’s tumour management.