Evaluation of asymptomatic microscopic haematuria--influence and clinical relevance of osmolality and pH on urinary erythrocyte morphology.

Abstract

To determine whether the morphological distinction between 'dysmorphic' and 'eumorphic' erythrocytes in urinary sediment differentiates microscopic haematuria (MH) from reno-parenchymal and post-renal bleeding. The erythrocyte morphology of 2145 urinary sediments from 1391 patients with MH was evaluated by interference-contrast microscopy and compared with the osmolality, pH and specific gravity of the urine samples. Compared with more concentrated urine specimens, samples of < 700 mOsmol/kg showed significantly lower percentages of dysmorphic erythrocytes; there was a similar reduction in this percentage at a pH > or = 7. In addition, erythrocytes lysed in diluted or alkaline urine and therefore, under these conditions, no diagnosis could be made. The assessment of erythrocytes in urinary sediment should be performed only under 'standard conditions', i.e. in concentrated and acidic urine, > or = 700 mOsmol/kg and a pH < 7. The presence of > or = 90% dysmorphic erythrocytes in patients with asymptomatic MH, the absence of proteinuria, a normal blood pressure and normal radiological examination indicates 'reno-parenchymal MH', requiring a long-term follow-up with a routine evaluation twice a year, but no immediate treatment in most cases. In contrast, the presence of > or = 90% eumorphic erythrocytes or even 'mixed' results (10-90% eumorphic erythrocytes) indicates 'post-renal MH', requiring a complete urological evaluation.