Early detection of renal scarring in children with suspected pyelonephritis: Comparison of diuretic MAG3 scintigraphy (F0) and DMSAScan

Background: Screening for patients at risk of renal scarring is a challenge in children with acute pyelonephritis (APN). Diuretic Tc-99m mercaptoacetyltriglycine (MAG3) scintigraphy with zero time injection of furosemide (MAG3-F0) was observed to display focal parenchymal disorders. The advantages of MAG3 include: lower radiation dose and short duration of the test. The aim of this study was to compare the role of Tc-MAG3 (F0) dynamic study and Tc-99m dimercaptosuccinic acid (DMSA) scan in early detection of renal scarring of children with suspected pyelonephritis in comparison to after-6-month Tc-DMSAscan as gold standard. Methods: 28 patients (56 renal units) with their first urinary tract infection (UTI) episode were evaluated prospectively for renal scarring with radioisotope scan. The patients were divided into 2 groups: Group A consisted of patients who underwent MAG3 scintigraphy in acute phase of pyelonephritis and Group B consisted of patients who underwent DMSA scan in this phase for renal cortical assessment. Follow up DMSA scan was performed for all patients in both groups 4-6 months after UTI episode. Results: The accuracy of MAG3-F0 scintigraphy and DMSA scan in detecting parenchymal changes in acute pyelonephritic phase were 89.3% and 96.4%, respectively. Positive predictive value (PPV) of both MAG3-F0 and DMSA was 100%. Whereas, negative predictive values (NPV) of MAG3-F0 and DMSA scan were 62.5% and 75%, respectively. Conclusion: Conclusively, if the MAG3 parenchymal image is abnormal, then there is renal damage but if this image is normal, a focal defect has not been excluded. Thus an abnormal MAG3-F0 precludes the need for a Tc-DMSA scan for detection of persistent renal damage in acute phase of pyelonephritis.