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Re: Are we requesting too many DMSA scans?

The recent article by Christian et al (1) highlights the value of clinical features in assessing the risk of renal scarring and therefore the need for DMSA scan after urinary tract infection (UTI). We recently performed a case note study to assess the recording of fever, malaise, recurrent UTI and urine culture results in children investigated with DMSA scan after UTI. Between April 1996 and October 1997 there were 171 DMSA scans in our hospital that fitted these criteria; 30 case notes could not be traced. There were 105 girls (74%) and 36 boys. Age when UTI was diagnosed ranged from 9 days to 15.3 years, mean 4.2 years (SD 3.2).

Urine culture results were:
UTI (>105 cfu/ml) 82 cases (58%)
contaminant ( <105 cfu/ml) 27 cases (19%)
no growth - 21 cases (15%)
no urine culture 11 cases (8%) cases.

There were 17 (12%) cases of definite or probable renal scar none of which followed a sterile or contaminated urine culture. Of the 141 case notes, there was no mention of fever in 48 (34%), and no mention of malaise in 76 (54%). In 69 case notes reviewed there was no mention of previous history of UTI in 14 (20%) cases. Of those with a history of fever 19% (10/53) had an abnormal DMSA scan compared to 10% (4/40) in those without fever. 18% (9/50) of those unwell at the time of UTI had an abnormal scan compared to 13% (2/13) of those not ill.

These data suggest that in a substantial proportion of cases the decision to request a DMSA scan is apparently not influenced by salient clinical features and urine culture results. In this series, it would appear that those children with sterile or contaminated urine cultures should not have had a DMSA scan. This would have saved the cost and burden of 48 scans, 34% of this series, over an 18 month period. It is unlikely that these findings are peculiar to our district.