What makes red cells dysmorphic in glomerular haematuria?

Glomerular Hematuria and the Utility of Urine Microscopy: A Review

Evaluation of hematuria and microscopic examination of urine sediment are commonly used tools by nephrologists in their assessment of glomerular diseases. Certain morphological aspects of urine red blood cells (RBCs) seen by microscopy may help in identifying the source of hematuria as glomerular or not. Recognized signs of glomerular injury are RBC casts or dysmorphic RBCs, in particular acanthocytes (ring-shaped RBCs with protruding blebs). Despite being a highly operator-dependent test, urine sediment examination revealing these signs of glomerular hematuria has demonstrated specificities and positive predictive values ranging between 90%-100% for diagnosing glomerular disease, although sensitivity can be quite variable. Hematuria is a commonly used tool for diagnosing patients with proliferative glomerulonephritis such as IgA nephropathy, antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, and lupus nephritis, sometimes even as a surrogate for kidney involvement. Studies examining the role for hematuria in monitoring and predicting adverse outcomes in these diseases have shown inconsistent results, possibly due to inconsistent definitions that often fail to consider specific markers of glomerular hematuria such as dysmorphic RBCs, acanthocytes, or RBC casts. A consensus definition of what constitutes glomerular hematuria would help standardize use in future studies and likely improve the diagnostic and prognostic value of hematuria as a marker of glomerulonephritis.

Urinary red blood cells: not only glomerular or nonglomerular

Two main types of red blood cells, isomorphic and dysmorphic, are found in the urine sediment, indicating nonglomerular and glomerular hematuria, respectively. Occasionally, however, other types of red blood cells such as sickle cells, anisocytes, poikilocytes, elliptocytes and dacryocytes can be seen in the urine sediment of patients with hematuria. This paper describes such cases reported in the literature in which such unusual urinary red blood cells have been found and the experience of the authors on this subject.

A useful new classification of dysmorphic urinary erythrocytes

BACKGROUND

Among dysmorphic urinary erythrocytes (D cells), G1 cells or doughnut-shaped erythrocytes with one or more blebs are considered to be reliable markers for glomerular diseases. However, although there are many D cells with cytoplasmic color loss and without blebs in the urinary sediment, the significance of these cells is not clear. In this study, we devised a classification system for D cells and examined the relation between these cell types and urinalysis data.

METHODS

We classified D cells into three types (D1, D2, and D3 cells): D1 cells showed a ring-like shape and severe loss of cytoplasmic color with protrusions or blebs; D2 cells showed a doughnut-like shape and moderate cytoplasmic color loss with protrusions or blebs; and D3 cells showed a doughnut-like shape and mild cytoplasmic color loss without protrusions or blebs. We calculated the numbers of D cells of each type in 45 patients with glomerular diseases and in 303 general outpatients. This was done by bright-field microscopy modified for the analysis of urinary sediment, and we also examined the significance of these cell types.

RESULTS

In the 45 patients with glomerular diseases, the numbers of D1, D2, and D3 cells correlated with urine levels of proteinuria and hematuria and numbers of cellular and fatty casts. Numbers of D1 and D2 cells correlated with urine concentrations of albumin and N-acetyl-beta-D-glucosaminidase, and the proportions of D1 and D2 cells in D cells increased with the activity of glomerular diseases classified by urinalysis data. Only the number of D1 cells correlated with the urine concentration of potassium, which may increase in hemolysis. In the 303 outpatients, the sensitivity of D3 cells and D1 and/or D2 cells (G1 cells) was 73% and 46%, respectively, for the detection of glomerular diseases and the specificity was 93% and 99%, respectively.

CONCLUSIONS

These data indicate that the D3 cell is a sensitive marker for glomerular diseases, and that D1 and/or D2 cells are markers for severe glomerular diseases.

Urine cytology in renal glomerular disease and value of G1 cell in the diagnosis of glomerular bleeding

The objectives of the present study were to evaluate the cytology of urine sediments in patients with glomerular diseases, as well as the value of G1 dysmorphic erythrocytes (G1DE) or G1 cells in the detection of renal glomerular hematuria. Freshly voided urine samples from 174 patients with glomerular diseases were processed according to the method used for semiquantitative cytologic urinalysis. G1DEs (distorted erythrocytes with doughnut-like shape, target configuration with or without membranous protrusions or blebs), non-G1DEs (distorted erythrocytes without the above-mentioned morphologic changes), normal erythrocytes (NEs), and renal tubular cells (RTCs) were evaluated. Erythrocytic casts (ECs) were counted and graded as abundant (>1 per high-power field) or rare (1 per 5 high-power fields). G1DE/total erythrocyte ratios were calculated by counting 200 erythrocytes including G1DEs, non-G1DEs, and NEs. Only abundant NEs were found in 13 cases; abundant G1DEs, non-G1DEs, NEs, and no ECs in 95 cases; abundant NEs, non-G1DEs, and ECs and no G1DEs in 31 cases; and abundant NEs, G1DEs and non-G1DEs, and rare ECs in 35 cases. In 130 cases in which G1DEs were present, the G1DE/total erythrocyte ratios varied from 10% to 100%. This parameter was greater or equal to 80%, 50%, 20%, and 10% in 58 (44.6%), 29 (22.3%), 28 (21.5%), and 15 (11.5%) patients, respectively. In all cases, the number of RTCs was within normal limits or slightly increased, and a variable number of non-G1DEs were present in 161 cases. Thus, abundant ECs and/or G1DEs with a G1DE/total erythrocyte ratio of 10-100% proved to be specific urinary markers for renal glomerular diseases.