Determination of mean glomerular volume in nephrectomy specimens

Area of Science:

• Nephrology
• Quantitative pathology
• Stereology

Background:

• Accurate measurement of mean glomerular volume (VG) is essential in renal pathology.
• Previous studies showed varied correlations between VG measurement methods in specific biopsy types.
• The relationship of these methods across different tissue types remained unestablished.

Purpose of the Study:

• To evaluate the correlation, agreement, and repeatability of four methods for determining mean glomerular volume (VG).
• To compare the Cavalieri, Maximal Profile Area (MPA), Disector, and Weibel-Gomez methods in whole rat kidneys.
• To assess the impact of furosemide treatment on VG measurements.

Main Methods:

• Whole rat kidneys were sectioned and VG was measured using Cavalieri, MPA, Disector, and Weibel-Gomez methods.
• Correlation was assessed via linear regression (p < 0.01), agreement by the line of identity (x=y) within 95% confidence intervals.
• Repeatability was determined using the coefficient of variation for each method.

Main Results:

• MPA (r=0.86), Disector (r=0.66), and Weibel-Gomez (r=0.87) methods all correlated with the Cavalieri method.
• No method demonstrated agreement with the Cavalieri method (i.e., yielded the same VG values).
• Repeatability varied: Cavalieri and MPA (7% CV), Disector (12% CV), and Weibel-Gomez (25% CV).

Conclusions:

• While MPA, Weibel-Gomez, and Disector methods correlate with Cavalieri VG, they do not provide equivalent values.
• Discrepancies may stem from inherent assumptions of each method regarding glomerular shape and size distribution.
• Method consistency within a study is critical, and tissue availability often dictates the choice of VG measurement technique.