Fig. 1

Graphic presentation of the renal function (serum creatinine, serum urea) during intensive treatment. First acute kidney injury was diagnosed when the patient was initially admitted to the hospital with creatinine levels of 90 µmol/L, which decreased to reference values for age with an intensive rehydration regimen (left arrowhead). At that time, kidney morphology was evaluated with ultrasound, which showed normal dimensions and echomorphology without dilatation of the urinary tract. Second (middle arrowhead) and third episodes (right arrowhead) were classified as acute kidney failure and occurred during liposomal amphotericin B treatment and during the first high-risk chemotherapy block when a significant delay (198-hour) in high-dose methotrexate (5 g/m²) metabolite excretion was noticed, resulting in transient rise of creatinine and cystatin C levels up to 125 µmol/L and 2.36 g/L, respectively (estimated Glomerula Filtration Rate 30 mL/min/1.73 m²). Creatinine levels returned to normal when replacing amphotericin B with voriconazole and monitoring complete methotrexate elimination. Apart from urine alkalinization, increased hydration, and administration of leucovorin, no other treatments were necessary to resolve acute kidney injury. Renal Tc-99m Diethyl Triamine Penta-Acetic scintigraphy scan revealed decreased clearance of radiopharmaceutical material (75 mL/min/1.73 m²), and chronic kidney disease grade 2 was diagnosed. The patient had previously (at age of 3) been followed by pediatric nephrologist due to congenital hydronephrosis, but renal function and morphology were reported normal. We presume the patient initially had reduced renal parenchymal reserve and was more prone to acute kidney injury during precipitating factors (dehydration and unadjusted drug doses). Further cytostatic and symptomatic therapy dose corrections (75% of the total methotrexate dose and avoidance of all nephrotoxic drugs) were consistently undertaken, and laboratory parameters carefully monitored (starting from green arrowhead), so no additional kidney function deterioration was observed