99mTc-DMSA renal scintigraphy in the diagnosis and follow-up of acute pyelonephritis in children.

The aim of the present thesis was to define and evaluate a strategy for identification of children who are at risk of developing progressive renal lesions after acute pyelonephritis. Tc-DMSA renal scintigraphy is widely accepted as the most sensitive method for detecting parenchymal lesions and diagnosing acute pyelonephritis. Qualitative and quantitative evaluation standards were elaborated to improve the interpretation of DMSA scintigraphy. The normal DMSA distribution pattern, the average background uptake, and scintigraphic kidney length according to age were assessed in 95 presumably healthy kidneys. Furthermore, typical DMSA distribution patterns in acute pyelonephritis were assessed on 65 kidneys in 38 children, and typical DMSA distribution patterns of 152 kidneys with vesicoureteric reflux in 101 children with and without previous pyelonephritis. Measurement of scintigraphic kidney length, width and volume was validated in piglets and on a kidney phantom. The scintigraphic kidney length was found to be an accurate measure of renal size, whereas kidney width and volume were less reliable, at least on small kidneys. Criteria of kidney swelling in acute pyelonephritis were defined, and found to be beneficial for identifying reinfections in the absence of clinical symptoms. In 34 children with acute pyelonephritis quantitative and qualitative DMSA scintigraphic findings were correlated to clinical symptoms and laboratory data, in the acute stage and at follow-up. We found that a quantitative DMSA scintigraphy in the acute stage of pyelonephritis and again after one year will identify children who are at risk of developing progressive renal lesions. Qualitative assessment of DMSA distribution pattern is not reliable enough in this respect