AN ALBUM OF URINARY MICROSCOPY IMAGES IN A CLINICAL CONTEXT
G.B. Fogazzi, Milan, Italy
S. Verdesca, Milan, Italy
Good morning Ladies and Gentlemen. Welcome to this Compact Primer on an album of urinary microscopy images in a clinical context.
The course will include a short introduction and then the presentation of six clinical cases for which the urine sediment examination has been of particular importance or of particular interest.
What is the situation of urine sediment examination today? It is mostly performed in central laboratories, a fact which is very often associated with too many samples (up to several hundreds) per day; the lack of a proper methodology which is, a standardized method for urine handling; the lack of a proper equipment, namely, phase contrast microscopy and polarized light; and the examination of the samples far from the bedside of the patient. For all these reasons, the overall quality of the test is rather poor.
In central labs, urine sediment examination is performed mainly for screening purposes, on samples which are in most cases normal. Today, the largest laboratories use automated instruments to screen the urine. These instruments are able to examine large numbers of samples in short times (up to 100/hour), and supply acceptable results for normal samples and samples with mild to moderate changes. On the contrary, for the most abnormal samples, such as those supplied by the renal patients, the examination by manual microscopy is still needed. At present, there are two such types of instruments. One is Sysmex UF 100, which is based on cytofluorimetry, the other instrument is Iris iQ200, which is based on images taken by a videocamera. A third instrument, SediMax, is being launched into the market by A. Menarini Diagnostics.
To conclude on urinary sediment today, this diagnostic tool is too often neglected even by us nephrologists. I believe that many of us have forgotten the important clinical information it can supply in the everyday practice.
We in our unit at the Ospedale Policlinico of Milano, examine urine sediment ourselves. We examined about 2300 samples per year, 2 - 25/day. Very small numbers if compared to those seen in the central labs. However, most of our samples are pathologic, deriving from our ward and clinic.
In our lab, there are 4 persons involved in urine sediment examination. Two doctors (myself and Simona Verdesca), one biologist (Giuseppe Garigali) and one clinical technician (Daniela Croci). We currently use phase contrast microscopy and polarized light, which makes the use of stains useless. Since we deal with small numbers of samples, we do not need automatic instruments. We are always very interested in clinico-pathological correlations and we are strongly involved in educational activities.
In Italy, we have been running a national program on External Quality Assessment (EQA), which is called “Urinalysis Performance”. This is now in the 6th year of activity and enrolls more than 400 laboratories. We have also been running many theoretical and practical courses, whose features and results we have recently described in a paper published in Clinical Chemistry and Laboratory Medicine (2007;45: 407-412).
As part of our educational activity there also is a course called “Bedside urinary microscopy”, which was published in NDT Educational in 2006 and 2007. It is in 6 parts and describes in detail all the aspects of urine microscopy. If I consider the number of the downloads, more than 24,000 altogether, I can say that it has been a very successful course.
And now the clinical cases. We will present 6 clinical cases, which will show you how important and interesting the examination of the urine sediment can be in the clinical context.
The first two cases will be presented by Simona, who is a junior nephrologist, then I will present the other 4 cases. We have planned a discussion after the first two cases, another discussion after cases 3 and 4, and a final discussion. Please Simona, you can start.
This is the first case.
In September 1997, we examined the urine sample of an outpatient whose urine was positive, by dipstick, for albumin (+) and haemoglobin (+++). The urine sediment contained 50-60 erythrocytes and 3-5 leukocytes per high power field (400x) and more than 1 cast/low power field (160x). The casts were hyaline, granular, epithelial, and erythrocytic. In addition, there were many renal tubular cells, 3-5 per high power field. All these findings were consistent with a nephritic sediment associated with many renal tubular cells.
This slide shows the renal tubular cells (arrows) we found in the urine, together with a fragment of tubular epithelium (arrowhead). As you can see, the tubular cells are characterized by one central nucleus and many cytoplasmic granules.
We didn’t know anything about the patient, but we were worried by the possible clinical correlates of the urine sediment findings. Thus, we attached a note to the report in which we suggested the patient to contact us as soon as possible. The day after, a boy turned up who said that the urine belonged to his father, who was under clinical evaluation for a right lumbar pain of unknown origin. At this point, we asked the patient to supply a new urine sample and to check his renal function. The new urine sediment was the same as before, while the serum creatinine turned out to be 1.8 mg/dl, clearly higher than that found one month before (1.1 mg/dl). Therefore, we hospitalized the patient to perform the renal biopsy.
The renal biopsy contained 21 glomeruli, 3 of which were sclerotic, 3 others showed focal fibrinoid necrosis, and 2 others showed segmental cellular crescents.
The interstitium showed a focal mononuclear cellular infiltrate without tubulitis. Many tubules, some of which were filled with erythrocytic casts, showed a widespread epithelial damage and a focal detachment of the epithelium from the tubular basement membrane. The vessels were unremarkable. Immunofluorescence was positive only for fibrinogen in the areas of fibrinoid necrosis.
These are some details of the lesions we found in the renal biopsy: a glomerulus with an area of fibrinoid necrosis (arrow).
Several tubules filled with erythrocytic casts (arrows).
Tubules with the detachment of the tubular epithelium from the tubular basement membrane (arrows).
The loss of a large portion of tubular epithelium (left) and, on the right, the severe damage of tubular epithelium (arrows).
Based on the findings shown above, a pauci-immune necrotizing glomerulonephritis associated with acute tubular necrosis was diagnosed. Interestingly, we also found a pANCA positivity in the blood.
Therefore, we started a treatment with methylprednosolone pulses (500 mg each for three consecutive days) followed by oral prednisone (0.5 mg/Kg/day) and oral cyclophosphamide (1.5 mg/Kg/day).
In June 1998,ten months after the diagnosis, the serum creatinine was 1.2 mg/dL, the urinary sediment was normal, and proteinuria was absent.
In my opinion, this case is interesting because it shows us how the urinary sediment findings mirror what happens in the kidneys. In fact, the fibrinoid necrosis causes the extravasation of erythrocytes within the Bowman’s spaces, which is the causative mechanism of haematuria. Furthermore, the extravasation of erythrocytes into the tubular system and the entrapment of erythrocytes within the matrix of the forming casts explains the presence of erythrocytic casts, both in the renal biopsy and in the urine.
Finally, the epithelial tubular damage, secondary to the glomerular lesion, causes the detachment of the tubular cells from the tubular basement membrane, which explains the presence of many tubular cells in the urine.
As to renal tubular cells, we know that they can be found in the urine in a wide spectrum of renal diseases. The presence, or not, of other urine sediment particles is very helpful for a differential diagnosis.
The co-presence of dark granular and epithelial casts without other urine particles is suggestive for a pure type of acute tubular necrosis, as can be found in hypovolaemia.
On the contrary, the co-presence of crystals may be the marker of a crystalluric acute renal failure, as it can occur in acute uratic nephropathy (uric acid crystals), ethylene glycol poisoning (calcium oxalate crystals), congenital deficiency of the enzyme phosphoribosyltransferase (2,8 di-hydroxyadenin crystals), or some drugs (amoxycillin crystals, acyclovir crystals, etc).
The co-presence of white blood cells and leukocytic casts may suggest the presence of an ongoing acute interstitial nephritis.
Finally, the co-presence of red blood cells and erythrocytic casts is suggestive, as in this case, for a proliferative/necrotizing glomerulonephritis.
In my opinion, this case is educational for several reasons.
First, if we had performed urinalysis only by dipstick, we would have missed the renal tubular cells, the fragments of the tubular epithelium, and the erythrocytic casts, particles which led us to suspect the presence of a severe, active, and treatable renal disease.
Second. It was the examination of the urinary sediment by a nephrologist expert in the field which raised the suspicion of a severe renal disease. Thus, the examination of the urinary sediments by a nephrologist has an added value compared with the examination carried out by persons who don’t know the clinical and pathological correlates of the urinary findings. For this reason I believe that in each renal unit there should be at least one nephrologist expert in urine microscopy.
Third. The finding of a nephritic sediment and/or many renal tubular cells is always suggestive of an active and severe renal disease and should prompt further action.
In conclusion, this case teaches us that a skilful and motivated urine sediment examination can save a patient from a progressive renal disease.
All the details of this case can be found in this paper, which was published in June issue of Nephrology Dialysis Transplantation (2007; 22: 1778-81).
Besides our paper, there is another paper in the literature which deals with the urinary sediment findings in patients with vasculitis
This paper by Fujita and co-workers describes 6 patients with Wegener’s granulomatosis, for whom a strict correlation between the level of red blood cells in the urinary sediment and the renal activity of the disease was found. This slide shows what happened in one of the 6 patients. The patient had a relapse of the disease, as demonstrated by erythrosedimentation rate (ESR) and C reactive protein (CRP) levels. Interestingly, this was associated with the increase in the number of the erythrocytes in the urine (gray dotted columns). When, under the effect of the treatment with prednisolone and cyclophosphamide, the disease improved, the number of urinary erythrocytes decreased.
These are the other 5 cases described by Fuiita and co-workers. Similarly to what shown for the patient described in the previous slide, in four patients there was a close correlation between ESR and red blood cells in the urine. On the contrary, in another patient (bottom), ESR levels increased without any change in the number of urinary red blood cells. The explanation for this discrepancy is that in this patient ESR had increased due to a pneumonia in the absence of a relapse of systemic vasculitis. Thus, in Wegener’s granulomatosis, the number of urinary red blood cells seems to be more sensitive and more specific than ESR and PCR for the monitoring of activity of the renal disease.
THE SECOND PART WILL BE PUBLISHED ON MARCH 6TH, 2008