Anencephals as organ donors

"Both kidneys of an anencephalic newborn were transplanted into a 23-year-old male patient <...> 3 years after transplantation, the patient is doing well, <...> the level of creatinine is 1.5 mg/dl, and creatinine clearance is 52 ml/min" https://pubmed.ncbi.nlm.nih.gov/7026253/ 1981y.
Normal values for creatinine is 0.7 to 1.3 mg/dL[1], for creatinine clearance 97 to 137 mL/min[2].