SN Wong, NKC Tse, KP Lee, LCK Leung, WKY Chan, S Chim, SF Yuen, BCK Pau, KW Lee, HM Cheung, CMS Yip

Abstract

The purpose of follow up imaging study after first febrile urinary tract infection (UTI) is to detect urological abnormalities that need timely diagnosis and treatment. Recent guidelines attempt to recommend imaging in high risk children while avoiding unnecessary investigation in children who do not need them. This study retrospectively surveyed a local cohort of 820 children who had first febrile UTI when aged below 24 months and who had underwent full imaging studies. Significant urological abnormalities were found in 58 patients (7.1%), including 9 requiring surgical treatment, 37 with grade IV-V vesicoureteral reflux (VUR) and 12 with severe renal scarring. Four imaging strategies were tested in terms of number of imaging needed and the risk of missing the 58 target patients: The first strategy (ultrasonography (USG) for all patients and voiding cystourethrogram (VCUG) for those with abnormal USG or UTI recurrence) would need VCUG in 87 patients and missed 24% of the target patients (1.7% of whole cohort). The second strategy (USG for all patients and VCUG for those with clinical risk factors or USG abnormalities or UTI recurrence) would require 272 patients undergoing VCUG and missed 12% of the target patients (0.8% of cohort). The third strategy (USG and a late dimercaptosuccinic acid (DMSA) scan for all patients, and VCUG for those with USG or DMSA abnormalities or UTI recurrence) would require 133 patients undergoing VCUG and missed 12% of the target patients (0.8% of whole cohort). The last strategy (USG and late DMSA for all patients, and VCUG for those with clinical risk factors or USG or DMSA abnormalities or UTI recurrence) would require 298 patients undergoing VCUG and missed 8.6% of the target patients (0.6% of whole cohort). Conclusion: It is clearly not cost-effective to do full imaging (USG, VCUG and DMSA) in all young children after first febrile UTI. However, the extent of workup depends on the doctors' and the parents' value judgement balancing the cost of imaging studies versus the risk of missing abnormalities. This report shows that UTI is indeed a signal of underlying abnormalities in 7.1% of patients. It also provides an estimate of the risk of missing such abnormalities with various imaging strategies. This will be useful for counselling parents on follow up plans for such children.