0.70, and obstruction of ureter appeared. Six of them were performed Anderson-Hynes procedure. Another patients refused operation and were treated by antibiotics and were observed. We found there were congenital pelviureteric junction stenosis at the six patients, and two of them were obstruction completely, and two of them accompanied abnomal pelviureteric junction. Histopathologic exam have found that there were acute damage of the kidney and extravasation of urine especially. All six patients recover after operation. Conclusion: Congenital hydronephrosis can express acute obstruction during chronic disease course and accompany by serious injury of renal cortices in a short obstructive time. The first and important symptom is abdomnalgia. The obstruction of pelviureteric junction may be caused and aggravated by urologic infection. So sometimes the obstruction can relieve temporarily through usage of antibiotics. But the obstruction can occur repeatly and the renal function will be reduced. It is necessary that emergency and sub-emergency surgical treatment should be considered when the patients with light hydronephrosis occur abdominalgia. " v:shapes="_x0000_s1026">1709