尿路感染发病率因年龄而不同,且各个年龄组有症状的尿路感染较无症状的菌尿症少。估计约50%菌尿症病人过去患过尿路感染。菌尿症在早产儿约占3%,婴儿1%,1～5岁1%,学龄儿童1.5%。尿路感染和无症状的菌尿症,除在新生儿中男多于女外,均多见于女性。在病因方面,细菌可从尿道进入膀胱,当有膀胱输尿管瓣功能不全,则细菌可由膀胱进入输尿管,并上行至髓质。急性肾盂肾炎通常 The incidence of urinary tract infections varies with age, and there is less urinary tract infection in all age groups than asymptomatic urinary tract infections. It is estimated that about 50% of patients with bacteriuria have had previous urinary tract infections. Bacteriuria accounts for about 3% of premature children, infants 1%, 1 to 5 years old 1%, 1.5% of school-age children. Urinary tract infections and asymptomatic bacteriuria, except in neonates more men than women, are more common in women. In terms of etiology, bacteria can enter the bladder from the urethra, and when the ureter flap of the bladder becomes dysfunctional, the bacteria can enter the ureter through the bladder and up to the medulla. Acute pyelonephritis usually