BEDSIDE URINARY MICROSCOPY
GIOVANNI BATTISTA FOGAZZI LECTURES SERIES
URINARY SEDIMENT: Part 6 and last: Contaminants and funny findings
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
A large number of particles can contaminate the urine, whose identification is important to avoid misclassifications and misdiagnoses. Some contaminants derive from the patient, while others derive from the laboratory, or from the environment. Herewith I will discuss the main contaminants of the urine.
Contaminants from the patient derive especially from genital secretions. These can contain different components such as erythrocytes, leukocytes, squamous epithelial cells, bacteria, candida, trichomonas vaginalis, or spermatozoa.
During menstruation, the urine can easily be contaminated with blood. Therefore, a urine sample from a woman during menstruation should always be considered as non suitable for examination and should be discarded. The erythrocytes which contaminate the urine during menstruation are typically isomorphic, i.e., of non glomerular origin (slide 178 and slide 26 of Part II). Before basing the diagnosis of microscopic haematuria on a urine sample supplied by a woman in fertile age, urine contamination from menstruation should always be ruled out. Contamination of the urine with blood can also occur during ovulation or for all gynaecological disorders associated with bleeding. It may also occur in men due to bleeding of the glans, foreskin, or urethra.
Vaginitis also causes the shedding in the urine of large-to-massive amounts of squamous epithelial cells of vaginal origin (slide 182). We consider this last finding as a practical and simple way to distinguish leukocyturia and bacteriuria due to contamination from leukocyturia and bacteriuria due to urinary tract infection. In this last condition squamous epithelial cells are absent or in mild amounts.
Candida can also be a finding of vaginitis. It is easily identifiable for the presence of “buds”, which are the daughter cells.
Trichomonas vaginalis is another possible causative agent of vaginitis. This protozoon is oval to round, somewhat larger than a polymorphonuclear leukocyte.
Its distinguishing morphological feature is the presence of five flagella one of which, bent backward, is linked to the body by an undulating membrane.
When alive, T. vaginalis can readily be identified due to the motility of the flagella and the rapid and irregular movements of the body across the microscopic field (slide 186). The same findings caused by vaginitis, in men can be due to urethritis or balanoposthitis.
Spermatozoa are often found in the urine after sexual intercourse (both in men and women) or after ejaculation. However, all the conditions associated with spermatorrhea (= involuntary discharge of semen without orgasm) can cause the presence of spermatozoa in the urine. Due to their unique shape, spermatozoa can easily be identified in the urine. During courses on urinalysis, I have often been asked whether the presence of spermatozoa in the urine can cause proteinuria. Recently, we have had the opportunity to follow a patient who had a massive and transient spermatorrhea (slide 187), during which urinalysis performed by dipstick showed +/++ albumin. The day after, when spermatorrhea reversed, the dipstick for albumin turned out to be negative. Thus, the answer to the above question would be yes, spermatorrhea may be associated with (non renal) albumin in the urine.
Pubic hair and even hair (slide 190) can occasionally be found in the urine. Due to their large size, their identification under the microscope is easily confirmed by the macroscopic examination of the specimen.
Microscopic fragments of cloth (slide 191) or synthetic (slide 192) fibres are not a rare finding in the urine. They usually derive from underclothes. Cloth fibres can still exhibit the texture of the cloth and can be coloured. Synthetic fibres are often birefringent under polarized light (slide 193).
Talcum powder, when applied to the genital or pubic area, may find its way into the urine. Talcum particles have a crystalline structure, have pleomorphic shape and size, and are birefringent under polarized light (slide 195).
Starch is the most common contaminant from the laboratory. It comes from the dusting powder used for the gloves worn by lab personnel. It has a crystalline structure, a polygonal to roundish shape, and a nucleus-like centre (often with a “Y” shape). Size can be very variable.
Under polarized light, starch structures are birefringent and show the so-called “pseudo Maltese crosses” which is, crosses similar to those due to lipids but with arms of irregular length.
Glass fragments are not rare in the urine. They derive especially from coverslips, which are made of very thin, and therefore fragile, glass. Glass fragments have very variable size and shape. With some experience, they are easily identified.
Air bubble are rather common, being due to the entrapment of air between the slide and the coverslip (see also slide 190). The skilful microscopist of the urine should be able to reduce the formation of air bubbles by placing the coverslip on the slide with gentle and aimed movements of the hands…
Dust, sand, and earth particles can all
contaminate the urine, especially in some geographic areas in some periods of
the year (an example based on personal experience: the period of the wind “harmattan”
But even in western and rich world the urine can be contaminated with particles deriving from the environment.
This is the case with pollens, which in Milan where I work, are more common during the spring season. Due to the large variety of trees and plants, pollens come with a large variety of shape and size. The slide shows the same type of pollen in three different conditions, “hairy” on the left, “semi hairy” in the middle, and “bald” on the right.
Alternaria, helmithosporium (slide 205), and cladosporium (slide 206) are all fungal spores which can contaminate the urine from the soil and plants, especially in some periods of the year (for alternaria, the period June to October in our experience).
Under this heading I have put a number of structures with a funny appearance, which I have found in the urine over the years. I have named these structures according to their appearance. The nature of some of these particles is clear to me, while for others I’m unable to find an identification. I hope that some readers of NDT-Educational will be able to help me to find a proper name for these mysterious particles.
This a cast, which contains packed cells (leukocytes, renal tubular epithelial cells), has taken the appearance of a question mark. As if it wanted to say “what renal disease does this patient have?”
I really don’t know what this shell-like structure is. Does anybody have an hypothesis?
This “elf hat” is nothing but a transitional cell from the deep layers of the urothelium with a vesicle coming out from the lower part of the cell. The vesicle is the result of degenerative processes.
These “specs” are in reality two transitional cells from the superficial layers of the urothelium, which are linked by a bridge of unclear nature.
This nice “butterfly” is a crystal of sulfadiazine which we found in the urine of patient under treatment with this drug for an HIV-related encephalitis.
This “swan neck” is probably a cell. However which cell it is I really don’t know. Again, I ask the help of the readers.
This is a classic “tadpole” cell as it may found in the urine of patients with an urothelial malignancy.
This “frog” id a dysmorphic erythrocyte as seen be transmission electron microscopy (a technique which I used extensively to investigate the urine sediments 12 years ago, when I spent a period of study in the renal unit of Guy’s Hospital, London, which at that time was directed by famous Professor Stewart Cameron).
These “daisies” are crystals made up of an unusual type of calcium carbonate. According to some authors they appear in the urine only once every 130 years! (see: Fogazzi GB, et al. Nephrol Dial Transplant 2004;19:1907-09).
What is this “star”? I guess it is a vegetal particle, but for a proper identification I would like to ask, once again, the help of the readers.
And now a “flower”. This is due to squamous epithelial cells gently arranged at the top of a mucus thread. This is the last slide of my last series. I thank everybody for the patience and the attention.