Analysis of Kidney Ultrasonographic Dimensions by Body Habitus and Position

Renal dimensions are an important assessment of the genitourinary tract and are used to evaluate critical aspects of renal growth and development. Understanding the effect of patient position is important for use and interpretation of these parameters.

This prospective study determines the effect of patient position and general body habitus on renal length and parenchymal area (RPA) in children undergoing renal ultrasonography (RU).

Between October 2010 and January 2011 children had RU in prone and supine positions. Bilateral renal lengths and RPA were measured. Pearson and Bland-Altman statistical analyses were used to examine correlation, presence of measurement bias, and degree of agreement between methods.

Renal lengths in both positions were complete for 201 right kidneys and 196 left kidneys. RPA were complete for both kidneys on 177 children. When compared individually, supine and prone measures for renal length and RPA show high correlation by Pearson analyses (Pearson >0. 96, >0. 89 respectively). When compared for method, Bland-Altman analyses of differences versus means show greater than 50% variance and represent wide limits of agreement with poor interrelation. Neither persistent systematic bias nor body habitus influenced results.

While Pearson analyses shows high correlation for supine and prone renal measures, Bland-Altman analyses for renal length and RPA show wide limits of agreement not allowing interchangeable use of prone and supine measurements. As such, RU imaging should specify standardized positions and benchmarks. These results provide guidance for standardizing RU measurements when renal size is used as an indicator of kidney health.

The Journal of urology. 2016 Feb 10 [Epub ahead of print]

Erik Kouba, Beverley Newman, Linda M Dairiki Shortliffe

Fellow in Genitourinary Pathology, Department of Pathology, University of Indiana. , Pediatric Radiology, Department of Radiology, Stanford University. , Stanley McCormick Memorial Professor and Chair Emerita, Pediatric Urology, Department of Urology, Stanford University, 750 Welch Road, Suite 218, Stanford, CA.