Abstract
Following the diagnosis of upper urinary tract infection (UTI) in infants, a radiographic workup is necessary to identify susceptibility to renal damage. However, there is incomplete agreement regarding whether the emphasis should be on the presence of acute parenchymal damage versus the presence of vesicoureteral reflux (VUR). Voiding cystourethrography (VCUG) was historically used to detect high-risk patients. This method is now referred to as the bottom-up approach (BUA), and relies on VCUG to identify lower urinary tract abnormalities and VUR. Only those patients diagnosed with VUR then undergo 99mTc-DMSA renal scan to assess renal scarring at the convalescent phase. As an alternative method, the top-down approach (TDA) targets the kidney with a 99mTc-DMSA renal scan to diagnose acute renal parenchymal involvement at the acute phase of the upper UTI. Patients with photon defects are subsequently referred for VCUG to assess VUR in addition to a late 99mTc-DMSA renal scan (at 3–6 months) to assess for permanent renal scarring. As each strategy carries advantages and disadvantages, it is difficult to declare the winner between BUA and TDA. Given the unavailability of 99mTc-DMSA renal scans at most local medical institutions in Japan, where infants with upper UTI are managed, the author considers that BUA is more practical for infants with upper UTI.
