Obstruction of the superior renal calyces due to intrarenal vascular compressions is assumed on the basis of a characteristic sharply defined oblique filling defect with or without blunting of the fornices. Scintillation camera renography shows prolonged retention in the superior collecting system of the involved kidney. 11 out of 23 children had a symptomatology of recurrent hematuria, other origins of hematuria were excluded. 5 patients had urinary tract infection, the remaining 7 had normal urinary findings. Renal function was always normal. There is no correlation between severity of blunting and hematuria. In contrast to other studies which included only patients with blunting and ectasis even cases without blunting of the fornices have a clinical symptomatology. Deterioration of radiologic appearance and kidney function was not found. Any idiopathic hematuria should be investigated for calyceal obstruction. Uncomplicated cases require no therapy, long term follow-ups with regard to complications such as urinary tract infection and urolithiasis are indicated.