Although MRU is not routinely recommended in the initial workup of antenatal hydronephrosis, some authors have argued that it can add value through improved anatomical imaging, for example, in the evaluation of hydronephrosis in the setting of atypical urinary tract anatomy, such as certain duplicated collecting systems or renal dysgenesis [74]. MRU can also adequately assess degree of obstruction [75]. One potential limitation of MRU is that there are systematic differences in estimation of split renal function compared with the gold standard MAG-3 renal scan in kidneys with severely diminished renal function [75] and kidneys with severe hydronephrosis [76]. VUR can be either primary or secondary to other urologic abnormalities. In patients with moderate or severe hydronephrosis found on neonatal US, VCUG has a role in the evaluation of urologic abnormalities that may need immediate care [12,20,28,29,50,57]. Furthermore, it can reveal other anomalies, such as a duplex collecting system, which help to determine whether the reflux is primary or secondary. Other infants with severe or bilateral moderate antenatal hydronephrosis may have VUR in isolation. There is higher risk for UTI in children with VUR [59]. Although the benefit of prophylactic antibiotics in this population is unknown, some authors recommend beginning antibiotics on these patients [26,60]. Nuclear Medicine Cystography Some studies have suggested equal sensitivity for Tc-99m pertechnetate radionuclide cystography and VCUG [46], whereas others have indicated that radionuclide cystography has improved sensitivity for VUR in infants up to 1 year of age [47]. Arguments for and against using radionuclide cystography are similar to that of VCUG for the female patient. DTPA Renal Scan Tc-99m DTPA is excreted primarily by glomerular filtration. Its extraction fraction is approximately 20% accounting for greater background, versus renal, activity compared to MAG3 [61].
Antenatal Hydronephrosis Infant. Although MRU is not routinely recommended in the initial workup of antenatal hydronephrosis, some authors have argued that it can add value through improved anatomical imaging, for example, in the evaluation of hydronephrosis in the setting of atypical urinary tract anatomy, such as certain duplicated collecting systems or renal dysgenesis [74]. MRU can also adequately assess degree of obstruction [75]. One potential limitation of MRU is that there are systematic differences in estimation of split renal function compared with the gold standard MAG-3 renal scan in kidneys with severely diminished renal function [75] and kidneys with severe hydronephrosis [76]. VUR can be either primary or secondary to other urologic abnormalities. In patients with moderate or severe hydronephrosis found on neonatal US, VCUG has a role in the evaluation of urologic abnormalities that may need immediate care [12,20,28,29,50,57]. Furthermore, it can reveal other anomalies, such as a duplex collecting system, which help to determine whether the reflux is primary or secondary. Other infants with severe or bilateral moderate antenatal hydronephrosis may have VUR in isolation. There is higher risk for UTI in children with VUR [59]. Although the benefit of prophylactic antibiotics in this population is unknown, some authors recommend beginning antibiotics on these patients [26,60]. Nuclear Medicine Cystography Some studies have suggested equal sensitivity for Tc-99m pertechnetate radionuclide cystography and VCUG [46], whereas others have indicated that radionuclide cystography has improved sensitivity for VUR in infants up to 1 year of age [47]. Arguments for and against using radionuclide cystography are similar to that of VCUG for the female patient. DTPA Renal Scan Tc-99m DTPA is excreted primarily by glomerular filtration. Its extraction fraction is approximately 20% accounting for greater background, versus renal, activity compared to MAG3 [61].