PURPOSE: The contralateral kidney is abnormal in up to 25% of patients with multicystic dysplastic kidney. Traditionally, anatomical and functional evaluation of the contralateral kidney has been performed with ultrasound and dimercapto-succinic acid renal scintigraphy, as indicated. Recently magnetic resonance urography has been used to evaluate renal anatomy and function in other urological abnormalities. We compared the results of magnetic resonance urography and ultrasound for evaluating the contralateral kidney in patients with multicystic dysplastic kidney and we describe the range of findings detected. MATERIALS AND METHODS: Patients with multicystic dysplastic kidney who underwent magnetic resonance urography were identified. Anatomical findings on magnetic resonance urography were analyzed and compared to those on renal ultrasound. Additional functional information derived from magnetic resonance urography was also recorded. RESULTS: We retrospectively identified 58 patients with a unilateral multicystic dysplastic kidney who had undergone magnetic resonance urography, of whom 54 also underwent ultrasound. Of the patients 19 (32.8%) had a contralateral abnormality. A discrepancy between magnetic resonance urography and ultrasound was seen in 9 patients (16.7%). Of these patients only 1 had a completely normal contralateral kidney by ultrasound on retrospective review. The incidence and range of parenchymal abnormalities was wider than previously reported. CONCLUSIONS: Contralateral abnormalities in children with multicystic dysplastic kidney are common and more definitively evaluated with magnetic resonance urography vs ultrasound. Renal ultrasound remains the most appropriate modality for the initial evaluation of children with multicystic dysplastic kidney, and magnetic resonance urography is recommended when a functional study is required either to confirm the diagnosis of multicystic dysplastic kidney or to evaluate suspected abnormalities of the contralateral kidney.
PURPOSE: The contralateral kidney is abnormal in up to 25% of patients with multicystic dysplastic kidney. Traditionally, anatomical and functional evaluation of the contralateral kidney has been performed with ultrasound and dimercapto-succinic acid renal scintigraphy, as indicated. Recently magnetic resonance urography has been used to evaluate renal anatomy and function in other urological abnormalities. We compared the results of magnetic resonance urography and ultrasound for evaluating the contralateral kidney in patients with multicystic dysplastic kidney and we describe the range of findings detected. MATERIALS AND METHODS:Patients with multicystic dysplastic kidney who underwent magnetic resonance urography were identified. Anatomical findings on magnetic resonance urography were analyzed and compared to those on renal ultrasound. Additional functional information derived from magnetic resonance urography was also recorded. RESULTS: We retrospectively identified 58 patients with a unilateral multicystic dysplastic kidney who had undergone magnetic resonance urography, of whom 54 also underwent ultrasound. Of the patients 19 (32.8%) had a contralateral abnormality. A discrepancy between magnetic resonance urography and ultrasound was seen in 9 patients (16.7%). Of these patients only 1 had a completely normal contralateral kidney by ultrasound on retrospective review. The incidence and range of parenchymal abnormalities was wider than previously reported. CONCLUSIONS:Contralateral abnormalities in children with multicystic dysplastic kidney are common and more definitively evaluated with magnetic resonance urography vs ultrasound. Renal ultrasound remains the most appropriate modality for the initial evaluation of children with multicystic dysplastic kidney, and magnetic resonance urography is recommended when a functional study is required either to confirm the diagnosis of multicystic dysplastic kidney or to evaluate suspected abnormalities of the contralateral kidney.