Follow-up of acute pyelonephritis in children by Tc-99m DMSA scintigraphy: quantitative and qualitative assessment.

Purpose: The author's goal was to create a system to identify children at risk for development of progressive renal damage.

Methods: Thirty-four children were examined with Tc-99m DMSA scintigraphy in the acute stage of an initial episode of pyelonephritis, after 6 months, and again after 1 year. The scintigraphic findings were correlated with clinical and laboratory data.

Results: All children had parenchymal defects in the acute stage: 93% of the kidneys and 85% bilaterally. After 6 months, the defects had diminished or disappeared in 66% of the kidneys. New defects appeared in 22%. At 1 year, no further improvement was seen in the kidneys, with an improved or unchanged pattern at 6 months. New defects appeared in 34%. Mean kidney activity uptake expressed as the percentage of administered dose (KU/AD), was low in the acute stage, increased at 6 months, with no further significant increase at 1 year. Eighty-three percent of children with urine cultures growing > or = 104 bacteria/ml at follow-up had decreased KU/AD values, whereas all children with urine cultures growing < 104 bacteria/ml had increased KU/AD values.

Conclusions: Quantitative assessment increases the sensitivity of Tc-99m DMSA scintigraphy. Follow-up with this method makes it possible to identify the children with decreasing renal tubular function who may be at risk for progressive renal damage. Moderate bacteruria of 104 bacteria/ml urine is associated with deterioration of renal tubular function.