Although it can be performed independently, MRU can also be performed at the time of structural MRI. In a study of 24 pregnant patients with symptomatic hydronephrosis, MRU was noted to show different appearances in physiologic hydronephrosis and pathologic obstruction [44]. Multiple authors suggest that noncontrast MRU should be considered after an equivocal or nondiagnostic US in symptomatic pregnant patients with suspected urolithiasis [6,17]. In a prospective study of 55 nonpregnant patients with hydronephrosis detected on US for urologic symptoms, excluding patients with abnormal renal function given contraindication for IVU, Muthusami et al [30] compared static heavily T2-weighted MRU to reference IVU and determined that MRU had high sensitivity and specificity for detecting (95% and 100%, respectively) and grading (Spearman correlation coefficient 0.92) hydronephrosis, as well as identifying the location of obstruction (90% and 99%, respectively) if present. The authors conclude that static MRU can replace IVU when the latter is contraindicated or technically difficult. The authors note that MRU sensitivity for hydronephrosis grading increased with grade of obstruction. Radiography Abdomen and Pelvis There is limited evidence to support the use of radiography of the abdomen and pelvis for initial imaging of pregnant patients with symptomatic hydronephrosis with unknown cause. Radiography Intravenous Urography There is limited evidence to support the use of radiography with IVU (also referred to as IVP) for initial imaging of pregnant patients with symptomatic hydronephrosis with unknown cause. Historically, IVP was used to evaluate symptomatic pregnant patients suspected to have renal obstruction; however, due to radiation exposure, IV contrast administration and increased usage of cross-sectional imaging, this study is considered obsolete in many settings [6].
Hydronephrosis on Prior Imaging Unknown Cause. Although it can be performed independently, MRU can also be performed at the time of structural MRI. In a study of 24 pregnant patients with symptomatic hydronephrosis, MRU was noted to show different appearances in physiologic hydronephrosis and pathologic obstruction [44]. Multiple authors suggest that noncontrast MRU should be considered after an equivocal or nondiagnostic US in symptomatic pregnant patients with suspected urolithiasis [6,17]. In a prospective study of 55 nonpregnant patients with hydronephrosis detected on US for urologic symptoms, excluding patients with abnormal renal function given contraindication for IVU, Muthusami et al [30] compared static heavily T2-weighted MRU to reference IVU and determined that MRU had high sensitivity and specificity for detecting (95% and 100%, respectively) and grading (Spearman correlation coefficient 0.92) hydronephrosis, as well as identifying the location of obstruction (90% and 99%, respectively) if present. The authors conclude that static MRU can replace IVU when the latter is contraindicated or technically difficult. The authors note that MRU sensitivity for hydronephrosis grading increased with grade of obstruction. Radiography Abdomen and Pelvis There is limited evidence to support the use of radiography of the abdomen and pelvis for initial imaging of pregnant patients with symptomatic hydronephrosis with unknown cause. Radiography Intravenous Urography There is limited evidence to support the use of radiography with IVU (also referred to as IVP) for initial imaging of pregnant patients with symptomatic hydronephrosis with unknown cause. Historically, IVP was used to evaluate symptomatic pregnant patients suspected to have renal obstruction; however, due to radiation exposure, IV contrast administration and increased usage of cross-sectional imaging, this study is considered obsolete in many settings [6].