They reported equivalence of MRU with renal scintigraphy for diagnostic evaluation of split renal function in moderately dilated kidneys, with a standard deviation of approximately 12% between the two; for severely dilated kidneys, they note a mean underestimation by MRU of split renal function by 4%. They conclude that substitution of DRG by MRU is acceptable for moderately dilated kidneys but remains questionable for severely dilated kidneys. Notably, most of the included patients were children <2 years of age, and the MRU technique used included a diuretic component. In a prospective study of 13 people without and 15 people with hydronephrosis, Wang et al [13] reported significant correlation between MRU and DRG estimations of single-kidney GFR and that MRU is comparable to DRG for estimation of GFR in the setting of hydronephrosis. They note that both MRU and DRG may somewhat overestimate global GFR in the setting of obstructive hydronephrosis. MRU Without IV Contrast Although there is limited evidence to support the use of MRU without IV contrast for initial imaging of patients with asymptomatic bilateral hydronephrosis or asymptomatic hydronephrosis in a solitary kidney with unknown cause, MRU without IV contrast is, in general, preferred over CTU in patients with renal impairment [15]. MRU without IV contrast is useful for investigating the etiology of hydronephrosis and can be combined with anatomical Hydronephrosis on Prior Imaging-Unknown Cause imaging to provide more information than anatomical imaging alone but does not provide the level of functional imaging attainable with MRU without and with IV contrast. Radiography Abdomen and Pelvis There is limited evidence to support the use of radiography of the abdomen and pelvis for initial imaging of patients with asymptomatic bilateral hydronephrosis or asymptomatic hydronephrosis in a solitary kidney with unknown cause. Radiography of the abdomen and pelvis is not considered useful in this setting.
Hydronephrosis on Prior Imaging Unknown Cause. They reported equivalence of MRU with renal scintigraphy for diagnostic evaluation of split renal function in moderately dilated kidneys, with a standard deviation of approximately 12% between the two; for severely dilated kidneys, they note a mean underestimation by MRU of split renal function by 4%. They conclude that substitution of DRG by MRU is acceptable for moderately dilated kidneys but remains questionable for severely dilated kidneys. Notably, most of the included patients were children <2 years of age, and the MRU technique used included a diuretic component. In a prospective study of 13 people without and 15 people with hydronephrosis, Wang et al [13] reported significant correlation between MRU and DRG estimations of single-kidney GFR and that MRU is comparable to DRG for estimation of GFR in the setting of hydronephrosis. They note that both MRU and DRG may somewhat overestimate global GFR in the setting of obstructive hydronephrosis. MRU Without IV Contrast Although there is limited evidence to support the use of MRU without IV contrast for initial imaging of patients with asymptomatic bilateral hydronephrosis or asymptomatic hydronephrosis in a solitary kidney with unknown cause, MRU without IV contrast is, in general, preferred over CTU in patients with renal impairment [15]. MRU without IV contrast is useful for investigating the etiology of hydronephrosis and can be combined with anatomical Hydronephrosis on Prior Imaging-Unknown Cause imaging to provide more information than anatomical imaging alone but does not provide the level of functional imaging attainable with MRU without and with IV contrast. Radiography Abdomen and Pelvis There is limited evidence to support the use of radiography of the abdomen and pelvis for initial imaging of patients with asymptomatic bilateral hydronephrosis or asymptomatic hydronephrosis in a solitary kidney with unknown cause. Radiography of the abdomen and pelvis is not considered useful in this setting.