Urinalysis is an important laboratory test that can be easily performed in the practice and is a considered part of a basic database. The results can be useful in several situations and are not only limited to those directly concerning the urinary tract.1
Urine microscopy is an integral part of a routine urinalysis to provide a comprehensive report of urine status. Although urinalysis is an immensely useful tool, it may still be the most overlooked test in veterinary practice.
Although urinalysis can reveal a great amount about an animal’s health, it is a demanding task due to the amount of time, space, and practice required, and it is not always possible to perform it optimally in the stressful daily routine of the medical practice. An analysis takes place mainly in an external laboratory, which is however critical, since by degradation processes, no more the original urine arrives in the laboratory, whereby the analysis and diagnosis could be falsified.1
That's why anvajo has developed a device, which is ideally suited for the routine urinalysis in the field. Learn in this text more about:
- What information can be gathered from urine microscopy?
- Prerequisites to ensure a correct microscopic urinalysis
- The microscopic analysis process of a urine sample
- Possible challenges in urinalysis with microscopic diagnosis tools
- How the vet fluidlab 1 can improve your microscopic examination analysis of urine samples
What information can be gathered from urine microscopy?
Urine sediment analysis gathers information on the conditions of the kidney and urinary tract. Pathological conditions may lead to infections, which can be detected in the urine sediment. For this reason, its analysis is of great importance in medicine.2
Urine sediment analysis not only provides information about the lesion of the kidney or urinary tract, but also gives information that may lead to the development of therapies for diseases in this area. A commonly used therapy for urinary tract infections is treatment with antibiotics. However, resistance to this treatment is becoming increasingly apparent. For this reason, research is currently being carried out into a further therapeutic option, using phages. However, this is only at the development stage.2
Since there is a wide range of diseases, a careful analysis of the sediment can support the veterinarian in diagnosing what disease the patient may have. However, to determine this precisely, additional chemical parameters need to be examined, since analyzing only the sediment is not sufficient.
There are several urinary tract infections. One of them might be acute cystitis. It is an inflammation of the bladder. The urine is then cloudy or there might be blood and other debris.3
Other components indicate whether the patient for example is dehydrated, has a catheter-associated urinary tract infection, suffers from bladder stones or a yeast infection. There are still various other diseases, whose identification can be supported by analyzing the urine sediment.3
Kidney inflammation can come from infections, but also from autoimmune disorders and toxins in the body. In this case the internal kidney structures become inflamed. As a result, a lot of white, but also red blood cells leak from the blood into the urine, where it can be detected by urinalysis.3
This indicates an abnormality of the body function since urine is usually known as a cell-free body fluid.
The appearance of white blood cells in the urine may also suggest a urinary tract infection, like a bladder infection.
Prerequisites to ensure a correct microscopic urinalysis
To ensure a correct microscopic urinalysis there are some requirements that need to be fulfilled. Therefore 10-15 ml should be collected from the running urine stream, which should not be interrupted. The urine is to be collected in a sterile container.
Usually, it should be the first urine of the morning that is collected, as it is the most concentrated. This makes it best suited for bacterial examinations, clinical analyses, protein diagnostics or the quantitative detection of substances. 4
These are the prerequisites for human urine. The best way to collect animal urine, is via cystocentesis, since free catch urine can lead to false results.4
After collecting the urine, a very critical preanalytical requirement is the turnaround time (TAT). It means the time interval from sample collection to the time of the resulting analysis report. Ideally, the sample should be processed within 30 minutes after collecting it.4
The microscopic analysis process of a urine sample
The microscopic analysis of a urine sample always starts with collecting it and analyzing it within 30 minutes after collection. This is important as degradation processes in the sample can lead to altered results. If this is not possible, the sample should be stored in the refrigerator, otherwise bacterial growth may occur. Furthermore, the storage in the fridge maximizes cell preservation.5
However, it is important that the sample is not stored in the refrigerator for too long (not longer than 24 hours), since crystals may develop over time. Before analyzing the sample, it should be brought to room temperature. Meanwhile the device should be prepared, prior to processing the sample.
The general procedure is making sure that there are no bubbles within the sample carrier or dirt on the sample carrier surface, that may interfere with the evaluation of the individual sediment particles, correct microscopic urinalysis can take place. In addition, good mixing and fast sample aspiration using a pipette are the basis for achieving accurate results. This way the sediment with a high density, such as crystals or casts, is prevented from rapidly settling again. Afterwards the sample can be pipetted on a glass slide and analyzed.
From preparation to documentation: The Analysis process
The first step of the analyses process is proper preparation which includes the following tools5:
- urine sample in sterile container
- 5 ml or 1 ml centrifuge tubes
- disposable plastic pipette
- glass slide
- slide coverslip
- paper towel
When all tools are prepared, the process can be started, beginning with
- mixing, by inverting the urine filled container
- transferring ~ 5ml of the sample to a conical tip centrifuge tube
- placing tube into centrifuge
- balancing it correctly and securing the lid
- centrifugation for 5 min at 450 g
Once the centrifugation is done, the sample can be prepared for staining (staining the sample is an option, but is not necessary, still it can be helpful to highlight urinary constituents.):
- removing tube from centrifuge
- removing supernatant with plastic pipette-without disrupting the pellet
- addition of one drop of stain to the pellet
- resuspending by gently swirling the tube
- Finally, the sample can be analyzed under the microscope by:
- transferring drop of stained sediment to glass slide
- placing coverslip on top of the drop
- decreasing intensity of microscope
- placing glass slide on the stage of the microscope
- performing examination first at x10 and then at x40
- examination and documentation of casts, cells, crystals, etc...5
How is the urine sample manually analyzed through the microscope?
Analyzing urine samples manually under the microscope is the most common way to examine urine. Urine microscopy is a routine task when it comes to diagnostic evaluation of sick patients.
The examination of urine manually includes macroscopic analysis, as well as biochemical and microscopic urine sediment examination. Whereby the latter deals with most technical difficulties.6
However, urine microscopy is performed using a light microscope, firstly with a 10x and then with a 40x objective. Decreasing the intensity of the lightning helps to increase refractility of the unstained urine elements. Additionally, phase contrast microscopes facilitate the differentiation of casts and mucus or bacteria, of amorphous particulate material and helps to identify hyaline casts.
At a low magnification the whole coverslip with the urine sample is analyzed by using the 10-x objective. This way casts, large crystals, large infectious agents, like parasitic ova and other constituents, like debris, mucus or other contaminants can be semi-quantified.
Subsequently, the change to a higher magnification follows. In this manner the structures, identified at the lower magnification and multiple random fields can be examined.
This magnification allows the semi-quantification of cells for example leukocytes, erythrocytes, epithelial cells, or sperm, as well as small crystals, small infectious agents, like bacteria or fungi and other constituents (fat droplets, debris, other contaminants).1
Extensive education and training of medical doctors and veterinarians is necessary for correct analysis. Often the analysis and evaluation of urine sediments, by means of manual urine microscopy, suffers from interobserver variability, both in human and veterinary medicine.6
Possible challenges in urinalysis with microscopic diagnosis tools
Urine testing reveals a lot of information about a patient's health, but so far there are only two options for obtaining it. On the one hand, the urine sample can be sent to a clinical laboratory for examination and on the other hand, there is manual microscopy that can be performed locally.
While the former one includes high costs and does not meet the requirements to examine the sample within a short time after collection, manual analysis poses some other challenges.
Manual urine microscopy requires a lot of space for the equipment such as a microscope or a centrifuge. Apart from that it is a time-consuming task, which does not fit into the busy everyday routine of an ordinary medical or veterinarian. It includes sample centrifugation, slide preparation, as well as reading and evaluating the results. Here the centrifugation may cause a loss of part of the cellular elements. Apart from that it often damages or even destroys fragile elements like hyaline casts.7
The examination of animal urine also offers a further challenge. This is because it is difficult to obtain sufficient samples in the first place, or even to obtain a sample at all.
The evaluation of the results is one of the biggest challenges, since it requires skilled operators, who perform the analysis always with the same accuracy and precision.7
Non-standardized testing procedures in veterinary medicine may foster errors
Non-standardized testing procedures may lead to a human error, which is somewhat likely. Therefore, it is of great importance that analysts work extremely precisely and adhere to strict instructions. An error in this very time-consuming task might have a significant impact on the outcome of the analysis, which in return costs money and even more time.
Since there is no standardized testing procedure for urine microscopy in veterinary medicine, the results of the examination may differ from person to person. Therefore, it would be necessary to be examined by more than one person to get a proper and relying on result.
Moreover, the cellular information of the sample can get lost, if it is not being analyzed immediately. Additionally, a storage in the fridge can cause the formation of crystals in the sample, what could distort the results.
All in all, it is hard to get precise and relying on results from a non-standardized testing method.8
The time and variety of equipment needed for the analysis may pose as a challenge to many doctors
Everyday routine in the practice is stressful and busy. In this case, urinalysis requires additional time, which is limited anyway. This may also lead to human error.
Small practices have the disadvantage that they may not have enough space occupied by the urinalysis equipment.
Since there is no standardized method, the results may be ambiguous and erroneous.
For this purpose, the fluidlab with its simple and fast handling as well as precise results offers an ideal solution. The fluidlab addresses the challenges of urinalysis with its small portable size and many other enhancements, which can make urine microscopy standardized.
How the vet fluidlab 1 can improve your microscopic examination analysis of urine samples
Short turnaround time
It is used for the most difficult and crucial part of the process - urine microscopy. Here, the small device intervenes directly at a critical point, the turnaround time. It is so important to keep the time between sampling and examination short because urine is not a suitable physiological environment for cells. The pH value varies, and ionic strength is present, which can lead to morphological changes in the cells and even cell lysis if the sample is stored for a long time.
Examination in situ without centrifugation
The examination can take place in the field and within a short time a reliable result can be obtained. Furthermore, the sample does not have to be centrifuged but the native urine sample immediately after its collection can be analyzed and thus eliminates the need for transport or any preanalytical sample processing.
The large interobserver variability is eliminated and human error is reduced.
The measurement with the fluidlab is simple and can be performed by anyone with little technical knowledge. The handling of the device is also simple and intuitive.
One of the most important features is that the fluidlab automatically evaluates the results and presents them in a comprehensible way. So, there is no need for subjective evaluation.
Small size and portability
In addition, the fluidlab with its minimalistic design and pocket size fits perfectly into smaller laboratories, which are struggling with space as well as into crowded veterinary offices full of many other analytical devices. Additionally, the small size gives veterinarians the opportunity to increase the level of home/field care services, reducing stress of their patients by examining them in their home environment.
Small sample volume
Another advantage of the fluidlab is that only a small sample volume is required to obtain significant results. This is especially useful for veterinary medicine, as it is difficult to obtain any sample at all from an animal.
1Becker, G. J., Garigali, G., & Fogazzi, G. B. (2016). Advances in Urine Microscopy. American journal of kidney diseases: the official journal of the National Kidney Foundation, 67(6), 954–964. https://eclinpath.com/urinalysis/overview/
2González-Villalobos, E., Molina-López, J., & Balcázar, J. L. (2022). Phage therapy for urinary tract infections: does it really work?. International microbiology: the official journal of the Spanish Society for Microbiology, 10.
3Herdon J. & Luo E. K. (2018). Why is there sediment in my urine? Healthline. https://www.healthline.com/health/sediment-in-urine#When-to-see-a-doctor [21.09.2020]
4Scharrel D. (2018). Urin-Untersuchung/Urin-Analyse. Frauenärzte im Netz. Berufsverband der Frauenärzte. https://www.frauenaerzte-im-netz.de/diagnostik/urin-untersuchung-urin-analyse/ [21.09.2020]
5The University of Bristol (2017). Urine Sediment Preparation. https://www.bristol.ac.uk/media-library/sites/vetscience/documents/clinical-skills/Urine%20Sediment%20Preparation.pdf [21.09.2020]
6Hernandez, A. M., Bilbrough, G., DeNicola, D. B., Myrick, C., Edwards, S., Hammond, J. M., Myers, A. N., Heseltine, J. C., Russell, K., Giraldi, M., & Nabity, M. B. (2019). Comparison of the performance of the IDEXX SediVue Dx® with manual microscopy for the detection of cells and 2 crystal types in canine and feline urine. Journal of veterinary internal medicine, 33(1), 167–177.
7Moeller, K. E., Kissack, J. C., Atayee, R. S., & Lee, K. C. (2017). Clinical Interpretation of Urine Drug Tests: What Clinicians Need to Know About Urine Drug Screens. Mayo Clinic proceedings, 92(5), 774–796.
8Fogazzi, G. B., Garigali, G., Pirovano, B., Muratore, M. T., Raimondi, S., & Berti, S. (2007). How to improve the teaching of urine microscopy. Clinical chemistry and laboratory medicine, 45(3), 407–412.