Methods for estimating the volume of individual glomeruli.

Area of Science:

• Nephrology
• Renal Pathology
• Quantitative Morphology

Background:

• The Cavalieri and maximal planar area (MPA) methods are standard for estimating glomerular volume.
• Prior research indicated MPA yields significantly higher volumes than the Cavalieri method.
• This study investigated the discrepancy in glomerular volume measurements between MPA and Cavalieri methods.

Purpose of the Study:

• To re-evaluate the relationship between MPA and Cavalieri methods for glomerular volume estimation.
• To assess the impact of glomeruli shape on volume measurement accuracy.
• To compare measurement consistency across species (humans and rats).

Main Methods:

• Measured glomerular volume using both Cavalieri and MPA methods on 1201 human and 281 rat glomeruli.
• Embedded tissue samples in Epon for precise analysis.
• Conducted mathematical analysis to determine the effect of non-spherical glomeruli shapes on volume estimations.

Main Results:

• MPA values were only slightly higher than Cavalieri values (14% in humans, 6% in rats).
• The relationship between MPA and Cavalieri values was consistent across individuals and species.
• Glomerular sclerosis or tubule connection loss did not alter the MPA/Cavalieri ratio.
• Mathematical modeling suggested ellipsoidal shapes, not spherical, explain the observed MPA/Cavalieri relationship.

Conclusions:

• The Cavalieri and MPA methods yield comparable glomerular volume measurements in both human and rat kidneys.
• The MPA method is a reliable alternative to the Cavalieri method for glomerular volume assessment.