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.

在首次伴有發熱的泌尿系統感染後，進行影像檢查旨在能儘早發現泌尿系統異常，並及時作出診斷和治療。近期的指引建議只對高危兒童進行影像檢查，從而避免對那些無需要檢查的兒童進行檢查。此調查回顧性分析本地820名年齡介乎24月大首次伴隨發熱的泌尿系統感染並進行了全部影像檢查的兒童。發現泌尿系統顯著異常共58人（7.1%），包括9人需接受手術，37人伴有 IV-V級膀胱輸尿管反流，12人伴有嚴重腎臟瘢痕。以所需的影像檢查的數目和漏診的58名目標病人，對4種影像檢查方法進行測試：第一種方法（所有病人進行泌尿系統超聲檢查，對超聲異常者或反覆泌尿系統感染者，進行排泄性膀胱尿道造影）需行87個排泄性膀胱尿道造影檢查，漏診了24%目標病人（即總人數的1.7%）。第二種方法（所有病人進行泌尿系統超聲，對臨床上有高危因素者，或超聲波檢查出現異常者或反覆泌尿系統感染者，進行排泄性膀胱尿道造影）需行272個排泄性膀胱尿道造影檢查，漏診了12%目標病人（即總人數的0.8%）。第三種方法（所有病人進行泌尿系統超聲及隨診進行DMSA掃描，對DMSA掃描異常，或超聲異常者或反覆泌尿系統感染者，進行排泄性膀胱尿道造影）需行133個排泄性膀胱尿道造影檢查，漏診了12%目標病人（即總人數的0.8%）。最後一種方法（所有病人進行泌尿系統超聲及隨診進行DMSA掃描，對臨床上有高危因素者，或DMSA掃描異常，或超聲波檢查出現異常者或反覆泌尿系統感染者，進行排泄性膀胱尿道造影）需行298個排泄性膀胱尿道造影檢查，漏診了8.6%目標病人（即總人數的0.6%）。結論：對所有患兒首次出現伴有發熱的泌尿系統感染後，進行所有影像檢查（泌尿系統超聲檢查，排泄性膀胱尿道造影，DMSA掃描）是缺乏成本效益的。然而，患兒往後需進行哪樣檢查，則取決於醫生及患兒父母對影像檢查的費用和漏診泌尿系統異常的危險性，两者之間的判斷價值取得平衡。本研究顯示泌尿系統感染患兒中，確實有7.1%患兒有經存在泌尿系統異常。本研究也對不同影像檢查方法漏診泌尿系統異常的危險性作出評估，這有助醫師跟患兒父母商議隨診計劃。