A Study of Tubular Fluid Effects to Dysmorphic Urinary RBCs in Glomerular Hematuria

ABSTRACT

PURPOSE: Urinary red blood cell morphology has been used to localize the site of hematuria in the urinary tract. But the pathologic mechanism for dysmorphic urinary red blood cells remains undefned. Our study was undertaken to investigate the mechanism of dysmorphic urinary RBCs in glomerular hematuria. We have attempted to reproduce in vitro the changes that occur in red cell morphology during passage through the renal tubule and to elucidate the role of urinary composition in determining morphology. METHODS: We examined a number of urinary samples under bright f eld microscopes with Wright's stain. 1) One drop of fresh venous blood was added to 1 ml experimental fluid, allowed to stand for 5 min and then assessed. The experimental fluids used were NaCl solutions in which the sodium concentration varied among 40 and 400mmol/L and similar saline solutions to which KCl(10, 50mmol/L), CaCl2(0.5, 2mmol/L), Urea(100, 400mmol/L) and pH(4, 8) had been added. We examined the RBC morphology in these solution. 2) In order to simulate passage of RBCs through the renal tubule, RBCs were initially suspended for 5 min in hypertonic solutions(NaCl 200mmol/L+Urea 70mmol/L+Urea 1000mmol/L). The RBCs were separated by centrifuging at 500rpm for 2 min in conical tubes, the supernatant was discarded and the RBCs washed and resuspended in a hypotonic solution(NaCl 60mmol/L) for 5 min. We added two urines(610mOsm/Kg H2O) to these solutions and then examined the RBCs morphology. RESULTS: The results were as follows; 1) Anisocytosis and hypochromia were found in NaCl 60mmol/L and 75mmol/L solutions and crenated RBC was found in Nacl 400mmol/L solution. But addition of potassium, calcium or urea and variation of the pH had no effect on red cell morphology. 2) when exposed to hypotonic solution, which simulated tubular condition(NaCl 60mmol/L), the RBCs became anisocytotic and hypochromic. These two features were particularly marked if cells were transferred to concentrated urine(610mOsm/kg H2O). CONCLUSIONS: It is evident that a hypotonic tubular condition is hostile for red cells and may be primarily responsible for hy0pochromia and anisocytosis of RBCs. Although two characteristic features of dysmorphism can be reproduced in vitro, a the bizarre deformity cannot be observed. Therefore passage of red cells through the hypotonic tubular segment alone does not account for the typical deformity. Because dilute urine specimens give a false impression by selective lysis of dysmorphic cells, concentrated urine is suitable for analysis of red cell morphology.