Renal sonography in the differentiation of upper from lower urinary tract infection

Increase in renal volume and asymmetry in kidney size determined by sonography proved to be a valuable diagnostic criterion for differentiation between infections of the upper and lower urinary tract in 175 children: acute bacterial interstitial nephritis (79) and lower urinary tract infection (96). Kidney volume in acute pyelonephritis increased to an average of 175% of normal. In 71% of cases, affected kidneys showed an enlargement of at least 2 SD when compared with a group of 325 children without kidney pathology. Most impressive kidney enlargement was seen during the first year of life. In 50% of cases, acute pyelonephritis caused a bilateral increase in renal size and/or distinct volume asymmetry. Kidneys of patients with lower urinary tract infections had a mean volume of 99.68% and a physiologic volume asymmetry comparable to normal kidneys.