[Differentiation between glomerular and non-glomerular erythrocyturia: what is the value of differential microhematuria diagnosis?]

A few years ago, a new and simple method has been proposed to help guiding the investigation of microhematuria. This method which consists in quantifying the percentage of deformed polymorphous erythrocytes in the urinary sediment using phase contrast microscopy allows to distinguish glomerular from non-glomerular erythrocytes. In this paper, we have reviewed the recent literature concerning this approach and have discussed the conclusions according to our own experience based on the analysis of 147 patients presenting with microhematuria. Our results demonstrate that this technique is still limited by the difficulty to obtain well-defined cut-off values which effectively differentiate renal from urologic diseases. Thus, only extreme results showing either the total absence or the presence of a very high percentage of dismorphic erythrocytes appear to be helpful for the physician. Despite the introduction of this new method, many patients with microhematuria are insufficiently investigated.