Bacteriuria was present in 46% of 742 nonpregnant women referred by general practitioners due to clinical symptoms of urinary tract infection. Impaired urinary concentrating ability and radiological signs of chronic pyelonephritis were most frequently found in patients with previous episodes of fever and flank pain. There was no correlation between the number of previous episodes of lower urinary tract symptoms and current signs of acute or chronic pyelonephritis. Only a minority of patients with laboratory signs of acute pyelonephritis, i.e. temporarily impaired concentrating ability or raised coli antibody titre, showed clinical symptoms of renal involvement. Among placebo-treated patients the clinical symptoms disappeared despite the persistence of bacteriuria, and it is stressed that relief of symptoms does not indicate success of treatment. During the follow-up, 39% of recurrent infections were asymptomatic.

Abstract. Maximum urine concentrating ability (MCA) has been determined after the administration of vasopressin tannate in oil and found to be over 800 mOsm/kg in 26 of 28 normal subjects. Subnormal MCA was demonstrated in 93 of 157 bacteriuric women between the ages of 16 and 65. Impairment of MCA was positively correlated with clinical symptoms of acute pyelonephritis (fever and flank pain), and with a raised coli antibody litre. In 115 of the patients MCA was determined again after five to twelve months. In 34% MCA had improved by more than 25%. The assumption that this indicates acute pyelonephritis was supported by the presence of other signs of acute pyelonephritis in most of these patients in contrast to the patients who maintained a normal MCA during he observation period. It should be noted that not only Gram‐negative rods, but also coagulasenegative staphylococci, may cause acute pyelonephritis. The recurrence rate was nearly the same in patients with normal and in patients with impaired MCA before treatment, but it was significantly higher among patients in whom MCA remained low or deteriorated during the observation period than in patients whose MCA remained normal or showed improvement.

Methods for the determination of leucocyte excretion in the urine have been studied, and an investigation has been made of the relationship between pyuria and bacteriuria. All of 42 women with no evidence of urinary tract disease excreted fewer than 400,000 leucocytes per hour, while 144 out of 152 women with bacteriuria excreted more than 400,000 leucocytes per hour, regardless of the type of bacteria isolated from the urine. Among these patients the excretion rate was found to be higher in those with impaired urine concentration ability, i.e. with signs of pyelonephritis. Pyuria can be diagnosed by estimation of the leucocyte excretion rate or by determination of the leucocyte concentration in the urine. There were more than 10 leucocytes per mm3 of urine in 97% of the specimens from 164 patients who excreted more than 400,000 leucocytes per hour. Ten or fewer leucocytes per mm3 were found in the urine from 92% of the 71 subjects who had excretion rates below 400,000 leucocytes per hour. With the technique employed for microscopic examination of the urinary sediment, the finding of three or more leucocytes per high‐power field indicates pyuria; if there are fewer than three, pyuria cannot, however, be ruled out.

Coagulase‐negative staphylococci were found in the urine of 14% of 193 non‐pregnant women between the ages of 16 and 65 with significant bacteriuria. The leucocyte excretion rate in the urine of these patients was increased and was found to be of the same magnitude as in cases of infection due to bacteria known to be pathogenic in the urinary tract. Pyuria disappeared as the patients obtained sterile urine. It is concluded that the patients were infected with coagulase‐negative staphylococci in the urinary tract. The majority of the patients had a depression of renal concentration capacity. There was good agreement between the concentration capacity and clinical symptoms normally regarded as indicative of pyelonephritis. It seems probable that coagulase‐negative staphylococci may cause pyelonephritis. Coagulase‐negative staphylococci were more frequently found in younger patients with urinary tract infection and were more frequent among patients without previous symptoms than among those with a history of recurrent urinary tract infection. In comparison with patients with bacteriuria with E. coli, patients with coagulase‐negative staphylococci obtained spontaneously sterile urine more frequently and more rapidly.

Abstract. A different prevalence of the most common E. coli O groups in primary and recurrent urinary tract infections has been reported. In the present study 219 non‐pregnant women with bacteriuria were followed up regularly in the Out‐patient Clinic after treatment. Two hundred and fifity‐five cases of reinfection were detected. Seventy‐seven per cent of the infections on admission were due to E. coli. as compared to 78% in reinfections. The proportion of infections due to the most prevalent O groups, 02, 04, 06, 075, was considerably higher on admission (56%) than in the reinfections (34%). This was due to some extent to exclusion of cases of recurrence with organisms identical to those found in the preceding infection. However, the main reason was a decrease in the prevalence of one serotype, E. coli 02:H4, during the observation period. This was probably caused by changes in the flora from which the urinary tract is infected.