Static and Functional MR Urography to Assess Congenital Anomalies of the Kidney and Urinary Tract in Infants and Children: Comparison With MAG3 Renal Scintigraphy and Sonography.

OBJECTIVE

The purpose of this study is to compare functional MR urography (MRU) with the results of ultrasound and radionuclide Tc-mercaptoacetyltriglycine (MAG3) scintigraphy in evaluating morphologic findings, split renal function, and urinary tract obstruction in pediatric patients.

MATERIALS AND METHODS

Pediatric patients with proven congenital anomalies of the kidney and urinary tract were included (n = 112). The morphologic findings of MRU were compared with previous diagnostic ultrasound findings. For evaluation of split renal function and urinary tract obstruction, MAG3 scintigraphy was used as a reference standard.

RESULTS

MRU provided detailed morphologic information of the whole urinary tract for all 112 patients. In 94.6% of cases (n = 106), diagnostic findings could be verified, and in 5.4% of cases (n = 6), more detailed information could be gained. Equivalent split renal function showed good concordance between functional MRU and MAG3 scintigraphy. However, in kidneys with restricted function (< 35%), functional MRU underestimated the remaining renal function, with a mean difference of 6.6% and an SD of 24.4%. For evaluation of relevant urinary tract obstruction, the sensitivity of functional MRU was 100%, specificity was 81.6%, positive predictive value was 70.8%, and negative predictive value was 100%.

CONCLUSION

Regarding split renal function, functional MRU shows a lack of accuracy in comparison with the clinical standard MAG3 scintigraphy, especially in patients with severely diminished function of one kidney. However, functional MRU allows an adequate assessment of urinary tract obstruction and a high-resolution morphologic evaluation of the whole urinary tract. Thus, functional MRU is suitable to add diagnostic value, especially as a complementary examination for complex individual cases in the presurgical state.