Introduction:
Neurofibromatosis type 1 (NF1) is an autosomal dominant condition that occurs at an incidence of 1/3,000 live births. The characteristic features are skin lesions known as café-au-lait macules, neurofibromas of any type, plexiform neurofibroma, freckling in the axillary or inguinal regions, optic glioma, Lisch nodules and a distinctive osseous lesion. Urinary tract involvement of neurofibromatosis is rare, and was reported in approximately 70 cases mainly with involvement of the urinary bladder; only 25 cases concerned the paediatric population.

Case report:
The case is presented of an 11-year-old boy with NF1, with the diagnosis of tumour of the abdominal cavity that had infiltrated the posterior wall and triangle of the urinary bladder. A double collecting system with third degree vesico-urinary reflux on the right side was additionally discovered. Voiding disorders that were not observed at the beginning appeared later. The patient had reduced bladder volume with abnormal uroflowmetry test. In the follow-up, dysfunction of the right kidney was observed.

Conclusions:
The case is presented due to the rare location of the plexiform neurofibroma that leads to lower urinary tract dysfunction and gradual disturbances of kidney function. The management of patients with plexiform neurofibroma is not well defined, and in the case of our patient will probably require cystectomy.