Renal dimensions measured by ultrasonography in children: variations as a function of the imaging plane and patient position

Abstract

The purpose of this study was to determine the effect of patient positioning on sonographic renal measurements and to test if the patient position alters the three-dimensional shape of the kidneys. The maximum longitudinal renal length and transverse renal width and depth were measured in the supine and prone position in 100 children (200 kidneys). Age ranged from 6 months to 16 years (mean age 5 years). The results were compared for statistically significant differences. The maximum measured longitudinal renal length was statistically significantly larger in the supine than in the prone position (supine position, left: 8.0 cm; right: 7.7 cm; prone position, left: 7.9 cm, right: 7.6 cm; P<0.001). There was no statistically significant change in the transverse diameters (width and depth, P>0.001) and renal volume ( P>0.001) in the supine vs. prone positions. Our results show that position-induced reshaping of the kidneys is unlikely to be responsible for the discrepancy in maximum longitudinal renal measurements comparing supine with prone positions. Position-dependent changes in the degree of filling of the renal calyces and pelvis as well as errors in caliper distance measurements for the different scan depths (supine vs. prone) are more likely to be responsible for the encountered differences. Consequently, we recommend to add prone renal length measurements in addition to the supine measurements. In follow-up examinations, renal length measurements should only be compared that have been collected in the same patient position.

Kidney growth in small-for-gestational-age infants: evidence of early accelerated renal growth

“…Measurements of kidney length (KL) were performed using 5-8 MHz linear or curved array transducers (7 MHz) (HDI Philips 5000). A single maximal longitudinal measurement of each kidney was obtained sonographically in the supine position [20][21][22]. Renal length measurement was performed because this method has been reported to have the lowest inter-observer variation and better reproducibility compared with sonographic volumetric estimations of the renal size, especially when comparing repeated measurements [23].…”

Assessment of serum cystatin C in children with congenital solitary kidney

“…Michel et al [45] found a significant difference in kidney length between the supine and prone positions. Therefore, we measured kidney length only in the supine position in all the children involved in the study.…”

Renal Measurements, Including Length, Parenchymal Thickness, and Medullary Pyramid Thickness, in Healthy Children: What Are the Normative Ultrasound Values?

“…The limitation of sonographically measured renal length and its interpretation in the context of published normative standards have been reviewed in detail elsewhere [15]. One of the major potential limitations discussed in the literature is the possible influence of patient position and imaging projection on measured renal length [16][17][18]. …”

“…Michel et al [17] compared the supine with the prone position and reported that renal length measured in children in the supine position is greater than that measured in the prone position. They suggested that this difference was due to position-dependent changes in the degree of filling of the renal calyces and pelvis, as well as errors in caliper distance measurements for the different scan depths (supine vs prone).…”