Urine Sediment Microscopy-2

Particles of the urinary sediment :-
In the urine sediment we can find cells, lipids, casts, crystals and microorganisms.

We have two groups of cells in the urinary sediment: the cells deriving from blood and the cells of epithelial origin. The cells deriving from blood include: erythrocytes, leukocytes, and macrophages. The epithelial cells include: renal tubular cells, transitional cells, and squamous cells.

Erythrocytes:- in the urine we can find two main types of erythrocytes: the so-called glomerular (or dysmorphic) erythrocytes and the so-called non-glomerular (or isomorphic) erythrocytes.

These are cells with irregular shape, size, and cell membrane, which differ remarkably from the image of erythrocytes we have stored in our mind.

Non glomerular or isomorphic erythrocytes i.e., erythrocytes with a spherical shape and regular contours, containing (green-bluish cells) or not (colourless cells) haemoglobin.

What is the clinical implication of distinguishing glomerular from non glomerular erythrocytes?
glomerular or dysmorphic erythrocytes were found in patients with haematuria caused by a glomerular disease, while non glomerular or isomorphic erythrocytes were found only in patients with hematuria of urological origin. Thus, it was concluded that the evaluation of urinary erythrocyte morphology could be used to identify the source of hematuria.

However, the evaluation of the urinary erythrocyte morphology is associated with some drawbacks. First of all it requires experience. Then, it is exposed to the risk of a low inter-observer reproducibility. In fact, there are investigators who consider a haematuria as glomerular when 2 erythrocyte subtypes are present, others who say that there must be at least 3 subtypes of erythrocytes, while others as we have just seen use a >80% cut-off, others use other cut-offs, etc.

Köhler and co-workers showed that there is a subtype of dysmorphic erythrocyte, which they called “acanthocyte”, which can be easily (and less subjectively) identified due to its shape of a ring from which one or more blebs protrude (slide shown below shows an acanthocyte as seen by scanning electron microscopy) and which they found to be a marker of glomerular bleeding.




the slide below shows acanthocyes on phase contrast microscope.





What is the main indication for the evaluation of urinary erythrocyte morphology in clinical practice?
It’s persistent isolated microscopic haematuria of unknown origin In this condition, the evaluation of red cell morphology helps in deciding whether the patient has to be submitted to a nephrological work-up rather than to a urological one. This saves to the patient inappropriate investigation such as cystoscopy for a patient with haematuria due to a glomerular disease.