early detection of renal scarring in children with suspected pyelonephritis: comparison of diuretic mag3 scintigraphy (f0) and dmsascan

abstract 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 aconsisted 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-dmsascan for detection of persistent renal damage in acute phase of pyelonephritis.