Relationship of ultrasonographically determined kidney volume with measured GFR, calculated creatinine clearance and other parameters in chronic kidney disease (CKD)

Introduction. Kidney length has traditionally been used as a predictor of chronic kidney disease (CKD); however, kidney volume (KV) rather than length has been emphasized by researchers as a true predictor of kidney size in states of good health and disease. Since KV can be assumed to be a predictor of kidney mass or remaining surviving nephrons in CKD patients, we theorized that the KV should reflect the functional capacity of the kidneys, i.e. the glomerular filtration rate (GFR). Methodology. Forty CKD patients were recruited and investigated. Measured GFR was determined by calculating the average of endogenous creatinine clearance (mCrCl) and urea clearance (mUrCl) while predicted GFR was determined using Cockcroft and Gault, Hull and Modification of Diet in Renal Disease (MDRD) equations. KV was assessed ultrasonographically using the formulae of Dinkel et al. and Solvig et al. for ellipsoid organ. The relationship between the KV and GFR was assessed using Spearman's correlation coefficient while Bland and Altman tests were used to assess intraobserver variation and agreement between measured and predicted GFR. Results. The results showed a weak but positive correlation between KV and various indices of GFR, best with measured CrCl (correlation coefficient ranged between 0.408 and 0.503; P < 0.05), and which was not improved after normalization for body surface area (BSA). We also found a significant correlation between the measured CrCl and various values of estimated CrCl. Conclusion. Ultrasonographically determined KV was found to correlate with GFR and hence can be used to predict it in established CKD, particularly in resource-poor settings.