Introduction:
The development of imaging tools, especially progress in ultrasonography, and modification of the design of the biopsy needles, help to improve the quality of diagnostic material and to reduce the risk of complications in the case of percutaneous kidney biopsy in children. The sensitivity of ultrasound imaging in detecting these complications, to a large extent depends on the technical aspects and the use of various imaging options. In the presented study, the complications after kidney biopsy are discussed and show the advantages of monitoring patients after the procedure of percutaneous kidney biopsy with routine use of doppler imaging on the basis of own experience, and review of the literature. Case-descriptions of complicated kidney biopsies in three children are presented. Special attention on the recognition of the presence of an arterio-venous fistula presence is emphasized, and the importance of detection of that complication reviewed. The diagnosis of fistula explained the observed clinical symptoms (erythrocyturia/hematuria), there was, in any case, no need for further surgical treatment. Careful monitoring of the biopsied kidney allowed the confirmation of spontaneous closure of the fistula after a period of several days or weeks. The proposed procedure allows the determination of the group of patients requiring prolonged monitoring. Key words: children, percutaneous kidney biopsy, perirenal haematoma, subcapsular haematoma, arterio-venous fistula