Background: Together with increasing life expectancy of patients with cystic fibrosis *CF*, there is a growing need to deal with unforeseen problems and complications. Among others renal dysfunction has become of great concern.
Aim: Evaluation of renal function in CF children.
Material and methods: We performed cross-sectional study on a group of 11 teenage inpatients with CF. Physical examination, past medical history analysis, renal function measurements and analysis were conducted in all of them. Renal assessment included: serum cystatin C and creatinine levels, measured and estimated creatinine clearance, estimated cystatin C clearance, urine indicators of crystallization risk and renal ultrasonography.
Results: One patient had elevated serum cystatin C level and diminished McIsaac equation. Renal ultrasound revealed non-congenital anomaly in 1 case - it was nephrolithiasis. All the individuals had elevated at least 1 urine indicator of crystallization risk.
Conclusion: There is a great need of good, standardized test of renal function in cystic fibrosis patients. The focus of research should turn towards finding a tool similar to faecal elastase, which is cheap, easy to perform, sensitive and specific, and can be used to confirm the diagnosis.