Urinary tract infection is probably the commonest bacterial infection. Although primary prevention is preferable to early diagnosis and treatment, in practice it is limited to the avoidance of unnecessary instrumentation of the urinary tract. Research on the defensive mechanisms of the urinary tract may widen the scope of primary prevention.

Asymptomatic infections of the urinary tract can be detected by screening for significant bacteriuria. The value of detecting these asymptomatic infections in pregnancy is well established since eradication of bacteriuria detected early in pregnancy prevents the development of acute pyelonephritis. The cost of antenatal screening for bacteriuria may well be off-set by the reduction of expenditure on hospital admissions for acute pyelonephritis. The value of bacteriuria screening amongst school children and non-pregnant adult women is undetermined. Long-term follow-up studies of bacteriuria children and adults are required in order to determine whether bacteriuria leads to progressive impairment of kidney function. So far studies of this kind suggest that significant bacteriuria in the adult is in most instances a non-progressive condition. In children, however, the long-term sequelae of untreated bacteriuria may be more serious since it may lead to impairment of kidney growth and renal scar formation particularly when the bacteriuria is associated with vesico-ureteric reflux. It seems likely that renal damage due to childhood infection lays the foundation for persistent bacteriuria in the adult. A controlled treatment trial of bacteriuria in childhood is urgently needed lest hypothesis be translated into action before proof.