This greater extraction fraction, versus DTPA, accounts for less background, versus renal, activity compared to DTPA. Because of its rapid renal clearance and primary excretion by the tubules on which furosemide acts, Tc-99m MAG3 is preferred over Tc-99m DTPA in patients with suspected obstruction or impaired renal function [61]. Tc-99m MAG3 renal scan is useful for the evaluation of severe grade 3 and 4 hydronephrosis and may be performed in concert with a VCUG study [20,29,53,62,63]. Tc-99m MAG3 renal scan provides information on renal function and urinary tract drainage based on split renal function [61]. Diuretic renal scan is used for diagnosis of multiple causes of obstruction, including primary obstructing megaureter [52,66-68]. Approximately 5% to 10% of antenatal hydronephrosis is attributable to primary megaureter [4,69] diagnosed by persistent ureteral dilation (>7 mm). Primary megaureter is classified according to the presence or absence of reflux and obstruction. Most will resolve spontaneously [20,70-72]. Surgical intervention is decided based on evidence of obstruction and depends upon T1/2 of time activity curve (T1/2 >20 minutes), decreased renal function (<40% differential renal function), deteriorating function (>5% change on consecutive renal scans), or worsening drainage on serial imaging. Tc-99m MAG3 renal scan can be used to monitor function over time, with a decrease in differential renal function on the affected side often serving as an indicator of a need for intervention [55,73]. MRI Abdomen and Pelvis There is no consensus on the role of MRU, performed without and with intravenous (IV) contrast, in patients with moderate to severe postnatal hydronephrosis especially before VCUG is performed.
Antenatal Hydronephrosis Infant. This greater extraction fraction, versus DTPA, accounts for less background, versus renal, activity compared to DTPA. Because of its rapid renal clearance and primary excretion by the tubules on which furosemide acts, Tc-99m MAG3 is preferred over Tc-99m DTPA in patients with suspected obstruction or impaired renal function [61]. Tc-99m MAG3 renal scan is useful for the evaluation of severe grade 3 and 4 hydronephrosis and may be performed in concert with a VCUG study [20,29,53,62,63]. Tc-99m MAG3 renal scan provides information on renal function and urinary tract drainage based on split renal function [61]. Diuretic renal scan is used for diagnosis of multiple causes of obstruction, including primary obstructing megaureter [52,66-68]. Approximately 5% to 10% of antenatal hydronephrosis is attributable to primary megaureter [4,69] diagnosed by persistent ureteral dilation (>7 mm). Primary megaureter is classified according to the presence or absence of reflux and obstruction. Most will resolve spontaneously [20,70-72]. Surgical intervention is decided based on evidence of obstruction and depends upon T1/2 of time activity curve (T1/2 >20 minutes), decreased renal function (<40% differential renal function), deteriorating function (>5% change on consecutive renal scans), or worsening drainage on serial imaging. Tc-99m MAG3 renal scan can be used to monitor function over time, with a decrease in differential renal function on the affected side often serving as an indicator of a need for intervention [55,73]. MRI Abdomen and Pelvis There is no consensus on the role of MRU, performed without and with intravenous (IV) contrast, in patients with moderate to severe postnatal hydronephrosis especially before VCUG is performed.