Renal concentrating ability in 5-year-old girls with covert bacteriuria.

those with radiological pyelonephritis) and those without reflux. Our relatively small numbers and high variability make analysis difficult, but the indications are that the osmolality rises throughout the day in the controls and 'no-reflux' group, but not in those children with reflux (Fig. 1). The mean maximum osmolality of the controls was 1070 ± 93 mOsm per kg (± 1 SD), in those children with infection but without reflux 1045 ± 171 mOsm per kg (±1 SD), and in those with reflux 837 ± 169 mOsm per kg (+ 1 SD) (Fig. 2). The two groups of children with urinary infection show significantly increased variation when compared with the controls as both include children with normal renal concentrating ability. Because of this variability the tests usually applied to means between groups are invalid. However, the variability in the two groups of children with infection is very similar; their means when tested show that of the reflux group to be significantly lower (1% level). Children with radiological evidence of vesicoureteric reflux and pyelonephritis have a mean of 735 ± 93 mOsm per kg(±1 SD). Children who had been treated and whose urine was free of infection were admitted to the ward for a 48-hour period for concentration tests to be repeated. In nearly every case the osmolality of the urine had increased, in some cases quite dramatically. These results are seen in Fig. 3.