Differenzierung Glomerulärer und nichtglomerulärer Hämaturie im Hellfeldmikroskop

Value of urinary erythrocyte morphology in assessment of symptomless microhaematuria

To assess the value of microscopic analysis of urinary erythrocyte morphology as the initial step in the investigation of patients with isolated symptomless microhaematuria, 316 consecutive patients were grouped according to whether they excreted eumorphic or mixed forms of erythrocytes or only dysmorphic forms. The former group was investigated fully, and urological disease was found in 85% of 123 patients. The 192 patients with exclusively dysmorphic erythrocytes in their urine and normal renal function (benign renal microhaematuria) were assigned to annual follow-up examinations of urinary red cell morphology and renal function, and subjected to invasive diagnostic procedures when a change was noted. In only 2 of the 132 patients followed up for at least 2 years did a new disease develop; this was easily identified at one of the annual examinations. Microscopic analysis of urinary erythrocyte morphology is therefore an effective method for identifying patients with symptomless microhaematuria needing specific diagnostic investigation.

In vitro generation of dysmorphic erythrocytes

In hematuria, dysmorphic red blood cells found in the urine sediment are known to indicate glomerular origin of bleeding. To better understand the mechanisms which might cause the typical membrane changes in dysmorphic erythrocytes in vivo, we have exposed normal human erythrocytes in vitro to an osmotic and enzymatic environment similar to that of the nephron. In addition, treated or untreated erythrocytes were exposed to a hemolytic environment. The morphology of the cells was evaluated by light and electron microscopy in comparison of that of dysmorphic erythrocytes obtained in vivo. Neither the passage of erythrocytes in sequence through various solutions each simulating the tubule fluid in a different part of the nephron, nor exposure to urinary or renal enzymes or to serum per se causes the typical membrane alterations. Upon exposure of passaged erythrocytes to a hemolytic environment, however, 50 to 90% of the cells become dysmorphic in a time and dose dependent fashion. By light and electron microscopy these dysmorphic erythrocytes obtained in vitro are indistinguishable from those obtained in vivo. In contrast, non-passaged red blood cells are not affected by the same hemolytic environment. We conclude that osmotically challenged erythrocytes exposed to a hemolytic environment develop dysmorphic membrane alterations.