the urinary sediment

The urinary sediment


•the document published by the European Urinalysis Group as a supplement of the Scandinavian Journal of Clinical and Laboratory Investigation (2000; Vol 60, Suppl 231)

•as well as a book (Fogazzi GB, Ponticelli C, Ritz E. The Urinary Sediment. An Integrated View 2nd Edition. Oxford , Oxford University Press, 1999)

The urinary sediment A correct urine collection

The patient has to: supply the first and/or the second urine of the morning

the second urine could be better – the overnight urine, due to its prolonged permanence in the bladder can favour the lysis of particles

avoid of strenuous physical effort in the hours preceding the test - may influence in various ways the findings (for instance by causing haematuria and/or cylindruria)

The urinary sediment The patient has to:

avoid contamination clean the external genitalia in an ordinary way

do not suggest special procedures - the more the procedures suggested are complicated, the less the patient is compliant

the male has to uncover the glans and female to spread the labia of the vaginacollect the midstream urineavoid urine collection during menstruation - high probability of blood contaminationuse a proper urine container


A proper urine container

a capacity of at least 50 to 100 mLan opening of at least of 5 cm to allow easy collection of urine for both men and womena wide base to avoid accidental spillage a cap to avoid leakage a label for patient identification

it is no more time for the patient to collect the urine into jugs, bottles, cans, etc


Why is standardization of the handling of the urine important? Because only with a standardized method we can obtain:

quantitative reproducible resultscorrelated significantly with the number of particles found by the counting chamber

Centrifugation - 400 G = 2,000rpm

The expression of particles as lowest/highest number seen by microscopic field for scientific results - number of the cells found over 20 high power field

The urinary sediment Why phase contrast?

on the right - bright-field, and on the left - phase contrastwith phase contrast the particles are much better seen against the background

than with bright-fieldand this without the use of stains!

the European Guidelines strongly recommends the use of phase contrast microscopy


Why polarized light?

Polarized light is extremely useful to correctly recognize the crystals

The urinary sediment uric acid crystals as seen by phase contrast microscopy and by polarized light

Under polarized light, uric acid crystals assume a typical polychromatic appearance, which is useful to identify them

The urinary sediment Polarized light is also important to correctly identify lipid particles

under polarized light appear as “Maltese crosses” -“shining” particles containing a “black cross” whose arms are regular and symmetricalthis feature allows the identification of lipid particles, especially when they come with an atypical appearance

The urinary sediment The urinary sediment report

the patient details

pH, density (or specific gravity) haemoglobin and leukocyte esterase as detected by dipstick

the particles: erythrocytes (with their morphological classification),leukocytes, tubular cells, transitional cells (from the deep and superficial layers of the uroepithelium), squamous cells, casts, lipids, crystals, bacteria, and yeasts

a space for a brief conclusive comment

high importance - to have in the report the findings obtained by dipstick


Why this?

to have in the report the findings obtained by dipstick

The urinary sediment an example

by microscopy - a low number of erythrocytes and leukocytes

which is in contrast with +++ haemoglobin and +++ leukocytes esterase

explanation for this discrepancy: low density the lysis of erythrocytes and leukocytes which therefore cannot be seen by microscopy


In contrast, in other instances we may have negative haemoglobin and many erythrocytes by microscopy

This may be due, for example, to the presence of large concentrations of Vitamin C in the urine, which reduces the sensitivity of dipstick for haemoglobin


Therefore, it is always important to match the findings obtained by dipstick with those obtained with microscopy and to try to explain them


Thus, the comment for the sample above is: ” Mild erythrocyturia and leucocyturia. Please note the discrepancy between dipstick for haemoglobin and leukocyte esterase and microscopy. This is probably due to cell lysis caused by low density.”


An important message !

examining the urine only by dipsticks or only by microscopy exposes to the risk of false results

This risk is reduced when both methods are used on the same sample


Since the early 1980s we know that in the urine we can find two main types of erythrocytes:

so-called glomerular - or dysmorphicso-called non-glomerular - or isomorphic


Dysmorphic erythrocyte

cells with irregular shape, size, and cell membrane


Dysmorphic erythrocyte

–differ remarkably from the image of erythrocytes we have stored in our mind


Non glomerular or isomorphic erythrocyte

with a spherical shape and regular contours containing (green-bluish cells) or not (colourless cells)

haemoglobin


Conclusion - the evaluation of urinary erythrocyte morphology could be used to identify the source of hematuria

glomerular or dysmorphic erythrocytes were found in patients with haematuria caused by a glomerular disease

non glomerular or isomorphic erythrocytes were found only in patients with hematuria of urological origin


•haematuria is of glomerular origin when it contains >80% dysmporhic erythrocytes

•haematuria is of non glomerular origin when >80% of erythrocytes are isomorphic


“Acanthocyte” - marker of glomerular bleeding

a subtype of dysmorphic erythrocyteeasily (and less subjectively) identified shape of a ring from which one or more blebs protrude

The urinary sediment an acanthocyte as seen by scanning electron microscopy

The urinary sediment acanthocytes can be identified by phase contrast


What is the main indication for the evaluation of urinary erythrocyte morphology in clinical practice?

Persistent isolated microscopic haematuria of unknown origin


Persistent isolated microscopic haematuria of unknown origin

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


Urinary lipids

a marker of GBM damage a consequence of lipid ultrafiltration due to an impairment of glomerular basement membrane (GBM) permeability it occurs in glomerular diseases

rarely- due to lipid storage diseases (Fabry disease)

The urinary sediment lipid particles within the cytoplasm of a proximal renal tubular cell after they have been ultrafiltered at glomerular level and reabsorbed by the tubular cells and organised into lysosomes

The urinary sediment A typical “oval fat body” = macrophages or renal tubular cells gorged with lipid particles

The urinary sediment A typical fatty cast - under polarized light lipid particles show the typical appearance of “Maltese crosses”.

The urinary sediment A typical cholesterol crystal


Low sensitivity for diagnosis

the urinary sediment

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