BEDSIDE URINARY MICROSCOPY
GIOVANNI BATTISTA FOGAZZI LECTURES SERIES
URINARY SEDIMENT: Part 4: Clinical practice I
G.B. Fogazzi, Milan, Italy
Dr G.B Fogazzi
Research Laboratory on Urine, Unità Operativa di Nefrologia
Fondazione IRCCS, Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena
The urinary sediment in the clinical practise.
For the diseases of the native kidneys the examination of the urinary sediment may be useful in a number of conditions for instance, in patients with persistent isolated microscopic hematuria the examination of urinary sediment can tell us if the hematuria is glomerular or non-glomerular. In patients with glomerular diseasesthe urinary sediment can tell us if there is a proliferative or non-proliferative glomerulonephritis. Or in patients with chronic glomerulonephritis, it can tell us if there is a flare up or not. The best example is patients with systemic vasculitis and renal involvement or lupus nephritis. In patients with acute tubular necrosis the examination of the urinary sediment can tell us if the tubular necrosis is pure or is associated with red blood cells and red blood cell casts which can happen in patients with acute extra capillary glomerulonephritis or if the acute tubular necrosis is associated with myoglobin casts, which can happen in patients with rash syndrome or as we have already said it may be associated with crystals which may happen in patients with crystal uric types of acute tubular necrosis. In urinary tract infection the examination of the urinary sediment can tell us if the urinary tract infection is involving just the bladder or in the case there are casts of white blood cells and tubular cell casts it can tell us if there is also a kidney involvement.
In this respect I would like to tell you what is our experience in 2 situations, in two conditions one is persistent isolated microscopic hematuria and the other one is the patients with proliferative and non- proliferative glomerulonephritis. So I will show you our results. In patients with isolated microscopic hematuria we performed this analysis in our lab. We in fact evaluated urinary red blood cell morphology only on request. It is not for all patients but only on request for patients with persistent isolated microscopic hematuria of uncertain cause. We evaluate about 250 sediments per year of patients with this condition. Patients who come mainly from our clinic and the department of paediatrics.
For each sample we first evaluate the morphology of 100 red blood cells and then give for each cell, we classify the cell as isomorphic or dysmorphic and among the dysmorphic we include acanthocytes. We consider hematuria as glomerular when there are at least 5% of acanthocytes or if these are not present when we find a mixed pattern, when there is a mixed pattern which we define as a situation in which at least 40% of red cells are dysmorphic or if there is no mixed pattern, we use the old criterion established by Fawcett in 1992. But we also for each patient, we also for erythrocytes casts which we express as number found in 50 low power fields.
This is an example. pH 5.8, 1.20 specific gravity, haemoglobin 2+ nothing else. Erythrocytes 6-12 power field. You see here we classify them 30/100 are isomorphic, 70/100 are dysmorphic and of these 70, 15/100 are acanthocytes or GR cells. Thus our comment is casts are not present, erythrocyte casts are not found, our comment is mild to moderate erythrocyturia without other particles. Due to the presence of 15% of acanthocytes hematuria is probably of glomerular origin.
Over the years we have accumulated an interesting series of patients. Between 1994-2003 we identified 15 patients, 10 children and 5 adults whose microscopic hematuria was defined as glomerular by our criteria after the examination of repeated urinary samples. We had 15 patients with 52 samples of urinary sediment. All of these patients at a certain point were submitted to renal biopsy.
What did we find? We found that the glomerular disease was present in 13/15 patients while 2 patients were normal by light electron and immunofluorescence microscopy at the biopsy. Thus we found a concordance between urinary microscopy and renal biopsy in 13 patients out of 15 which is 87% almost. But red cell morphology gave a false positivity in 13% of cases. What about the diseases which caused glomerular hematuria? 8 were cases of thin basement membrane disease. 3 patients had Alport, 1 patient had IgA nephropathy and 1 patient had an endoproliferative glomerulonephritis with C3 by immunofluorescence.
It was interesting to notice that of 15 patients 9 with 28 samples had always a glomerular hematuria. We examined several samples from the same patient and always we found glomerular hematuria but in 6 patients we found that hematuria was not always glomerular, so hematuria can change, we don’t know why but it can change over time. One time is glomerular, the subsequent time is isomorphic then it is again glomerular. For this reason it is important that we examine more than 2 or 3 sediments per patient. Thus out of 52 samples, 43 were glomerular which is 80% and 5 were not glomerular.
As to the best and worst markers of glomerular hematuria what did we find? We found that acanthocytes at least 5% were present in 88% of cases. While a mixed pattern as we defined before was present in 7% of cases. Dysmorphic hematuria more than 80% in 4.7%. The erythrocyte casts were rare in 7% thus our experience is that acanthocytes are the best and most frequent markers of glomerular hematuria, so we always look for acanthocytes first and then we follow all the other parameters.
The conclusion of our experience is this that there is a good agreement between urinary red cell morphology and renal biopsy findings 87% concordance. Acanthocytes at least 5% are the best markers of glomerular hematuria 88% of cases, while red blood cell casts are rare findings in spite of the fact that we have looked for them very intensively. We looked, we screened 50 microscopic fields at low magnification.
The urinary sediment in proliferative and non-proliferative glomerular diseases.
We started this study many years ago, 6-7 years ago because we wanted to answer a question. There is a statement and a common belief among nephrologists that it is usually possible to distinguish between a non-proliferative glomerulonephritis by the fact that by urinary sediment proliferative forms contain many red blood cells and erythrocyte casts while forms which are non-proliferative do not contain red blood cells they contain only a few red blood cells and red blood cell casts. So we wanted to give a definite answer to this problem, to this question.
Thus we started in 1999 this study which we selected patients with a glomerular disease and a severe cylindruria which was at least 1 cast per low power field. Each glomerulonephritis was then classified after renal biopsy was put into the group of proliferative or non-proliferative and for all cases the urine sediment was studied a few hours before renal biopsy using the standardised method I have shown you before.
For each sample we counted the erythrocytes, leukocytes and tubular cells over 20 high power fields at high magnification then we also looked for fatty particles, which were expressed as absent or present.
And for cast, for each patient we evaluated 100 casts and classified them as hyaline, hyaline-granular, granular, Waxy, Fatty, Erythrocytic, leucocytic and epithelial and each type of cast was expressed as absent or present and as number percent 100 as percent.
In this way we decided to study 100 cases. You see here the clinical features wide male to female is almost the same, wide age spectrum, wide creatinine spectrum and wide proteinuria spectrum.
52 patients fell into the group of proliferative glomerulonephritis and 48 in the group of non-proliferative glomerulonephritis. Proliferative were especially IgA nephropathy then 13 cases of lupus nephritis type 4 especially, MPGA in 5 cases, acute post-infectious in 5 cases etc. membranous was the main group of non-proliferative group and then we had a non-proliferative lupus nephritis 3 cases, 7 cases with family doses, 6 FSGS etc.
These 2 groups of patients differ from the clinical point of view for age, which was higher in non-proliferative patients, serum creatinine which on the contrary was higher in proliferative glomerulonephritis and urinary protein excretion, which was higher in patients with non-proliferative glomerular diseases.
What about the findings of the urinary sediment? You see here that patients with proliferative glomerulonephritis had a significantly higher prevalence of erythrocyturia and leukocyturia the field has more than 1 per high power field. The higher prevalence of tubular cells in the urine. A higher prevalence of erythrocyte casts and a higher prevalence of epithelial casts. It’s interesting here to notice that we found erythrocyte casts in 63% of patients, which is a figure similar to that reported by Doctor Köhler who had a figure of 86% of cases but you see here they were more frequent in patients with proliferative glomerulonephritis than in those without proliferation.
When we examined the quantitative data, again we found that hematuria was much more severe in patients with proliferative glomerular disease than in those without. Again the same was true for white cells, for tubular cells and again for red blood cell casts and epithelial casts, while fatty casts which were more numerous in patients with non-proliferative glomerulonephritis.
Thus using discriminant analysis based on the total number of red cells, white cells on 20 power fields and percent of erythrocytic casts, we were able to obtain a correct diagnosis of proliferative or non-proliferative glomerulonephritis in 80.7% for proliferative and in 85.4% for the non-proliferative group.
We can say that with the analysis of the urinary sediment we can discriminate the 2 groups of glomerular diseases with a sensitivity of 81% and a specificity of 79%.
And the independent variables for proliferative glomerulonephritis by multiple logistic regressions were found to be red blood cell casts more than one high power field with a very high odds ratio then white blood cells and red blood cells.
Thus with this study we can answer the question we raised before compared to non-proliferative glomerular diseases the proliferative forms are associated with a higher prevalence in their numbers of red blood cells, white blood cells, tubular cells, red blood cell casts and epithelial casts and by considering red cells, white cells and red cell casts it is possible to distinguish the two types of GD, of glomerular diseases with an 81% sensitivity and 79% specificity.
We are going on with this study we want to increase the number of cases, we had 100 cases before, we had 142 cases today. In order to identify the urine sediment profiles for the most frequent types of glomerular diseases we have now 28 patients with IgA nephropathy, 32 patients with membranous nephropathy and about 25 patients with lupus nephritis and we want to arrive to correlate the urinary findings in the main groups of glomerular diseases with the renal changes at biopsy including reactivity and cronicity index.
THE FIFTH PART WILL BE PUBLISHED ON JANUARY 25TH, 2007