Normal limits for renal mobility in children.

The range of vertical renal mobility measured in the recumbent and erect positions was established in 309 children (232 girls) with normal renal function, ages 2.5 to 15 years, hospitalized because of urinary tract infections. It was found that the degree of renal mobility changed nonsignificantly with age, ranging between 12 and 19 mm approximately. In girls ages 12 to 15 years, the mean renal mobility was greater ranging from 21 mm (left kidney) to 23 mm (right kidney). Excessive renal mobility (calculated in mm as kidney mobility greater than 2 SD over the mean value in a particular age group) was found in 13 patients (4.2% of the studied children) 11 of which were girls. The right kidney alone was involved in 76.9% of these cases. A statistically significant correlation was found between the age, body weight, and height of these patients and the degree of right kidney mobility. Since nephroptosis of the right kidney has also been reported, mainly in adult women, the obtained results suggest that this abnormality is constitutional rather than acquired in adult life.