Sedimentscopy: Microscopic Analysis of Urine Sediment

The microscopy of urinary sediment is a very important aspect in the evaluation of patients. The urine test can provide information not only on the kidneys and bladder, but on the liver, pancreas and other organs, analyzing a wide range of disorders. A small sample indicates the situation in which the organism is in general.

Urine has several solid microscopic elements, insoluble in suspension. These elements include red blood cells, white blood cells, epithelial cells, crystals, bacteria and parasites. When at rest, or after centrifugation, these elements settle and settle at the bottom of the container. They are known as urinary deposits or urinary sediments, so the analysis of these sediments is called sedimentcopy.

Through urine it is possible to discover many pathologies, in addition to helping diagnose infections and kidney diseases, even cases of chronic diseases, such as hypertension or diabetes. It is also useful for monitoring the disease and responding to treatments.

The exam identifies the appearance, concentration, as well as content of the sample.

ROUTINE URINALYSIS – NOMENCLATURES

One of the big discussions is trying to standardize an appropriate nomenclature for urine testing. Called by many as a routine urine test, it also receives the following names:

• Type 1 urine
• Urine summary
• Simple urine
• Physico-chemical analysis of urine and sediment
• EAS (abnormal elements and sedimentcopy),
• EQU (chemical urine test),
• ECU (common urine test)
• Partial urine
• PEAS (search for abnormal elements and sediment)
• Uroanalysis
• Uranisis

ASPECTS ANALYZED IN THE EXAM

Routine urine analysis consists of measuring the different parameters, both microscopic and chemical in the sample, for patient diagnosis using physical and chemical methods.

Thus, the urine test consists of three distinct phases: physical, chemical and sediment analysis.

• The physical analysiscomprises observation of appearance, color, density and occasionally odor of urine.
• The chemical analysiscan be performed classically with reagents prepared by the laboratory itself or with the dry chemistry use, the use of reagent strips.
• The sediment analysiscan be done by microscopy or by automated methodologies.

Although the appearance or the color can give some indication of the problem, microscopy allows a deeper analysis of the sample.

PREPARATION OF THE URINE SAMPLE

Under microscopy, a urine sample is centrifuged to obtain sediment. These can be used to examine the presence of epithelial cells, leukocytes, red blood cells, cylinders, crystals, bacteria and fungi.

Centrifugation is a physical separation process. It consists of a fluid sample that is subjected to centrifugal force in order to promote the separation of the components through the sedimentation of elements of different densities.

In relation to the routine urine test done in a classic (manual) manner, centrifugation is a pre-analytical procedure that should be performed under ideal conditions. This allows the sediment to be obtained within the standards necessary for the proper performance of the microscopic analysis.

To prepare a urine sample for microscopic analysis, a fresh sample of 10 to 15mL of urine must be centrifuged at 1,500 to 2,000 rpm for 10 minutes, according to recommendations of the Brazilian Society of Clinical Pathology / Laboratory Medicine ( SBPC / ML ). The supernatant is then decanted and the pellet resuspended. A drop is placed on the slide, K-cell slide or counting chamber for analysis under the microscope and cell counting .

K-cell blade

Counting chamber

Microscope slides

SEDIMENTS IDENTIFIED BY MICROSCOPY

The urine sediment must be reported qualitatively (types of cells, cylinders, crystals, organisms) and quantitatively (number of cylinders per small increase field and / or cells per high increase field). At least 10 to 20 microscopic fields must be observed and an average range reported.

Microscopic examination of urinary sediment can indicate the presence of a disease and, often, the nature and extent of the lesions.

Usually, a small number of cells and other formed elements can be detected in the urine. When there is an illness, the number of these elements increases significantly.

Here are the elements that are found in the urine:

Cellular elements

Urine can contain different types of cells, some derived from blood and others from the lining epithelium of the urinary system. The most common cell types observed are erythrocytes, leukocytes and epithelial cells.

Epithelial cells

It is common to find some epithelial cells. They can be of three distinct types: squamous, transactional and renal tubule cells.

Most have no clinical significance, representing a peeling of cells from the epithelial lining of the urinary tract. The finding of cells with nuclear or morphological atypias may indicate the presence of neoplastic processes. The presence of epithelial fragments and cells of tubular origin may be linked to processes of acute tubular necrosis and ischemic kidney damage.

Stained squamous epithelial cells. Bright field microscopy¹

Erythrocytes (red blood cells or red blood cells)

The presence of an increased number of erythrocytes in the urine is called hematuria (blood in the urine). It can be microscopic or macroscopic, depending on its intensity.

Hematurias can be transient and benign, but they can also indicate inflammatory, infectious or traumatic lesions of the kidneys or urinary tract.

The erythrocyte morphology is useful to help locate the source of the lesion, be it a kidney disease or anywhere else in the system or urinary tract.

Normal erythrocytes. Phase contrast microscopy (1-4). Bright field microscopy (5-8) ¹

Leukocytes (white blood cells)

They may be present in small amounts in normal urine. However, in high quantity it is called pyuria. Neutrophils are the most common type, but eosinophils and lymphocytes can also be seen.

Increased amounts indicate the presence of inflammatory, infectious or traumatic injuries at any level of the urinary tract. It can also be indicative of sample contamination. For this reason, genital contamination should always be excluded. It is necessary to observe which type of white cell is enlarged to search for the corresponding systemic or local cause.

Stained leukocytes. Bright field microscopy. ¹

Crystals

Crystals are formed from the precipitation of salts present in the urine by several factors, such as pH and concentration. They are a frequent finding in the analysis of normal urinary sediment.

There are crystals whose presence in the urine may be associated with some metabolic or infectious diseases, being considered pathological crystals. The same crystal, depending on the quantity, form of presentation and conditions of the urinary environment, can have different clinical meanings.

Some crystals represent a sign of physico-chemical disturbances in the urine or have specific clinical significance, such as cystine, leucine, tyrosine and magnesian ammonia phosphate. Crystals of medicinal origin and components of urological contrasts can also be seen.

Cystine is linked to the metabolic defect cystinuria, in addition to accounting for about 1% of urinary stones. As tyrosine and leucine are the result of protein catabolism, their appearance in the urine in the form of crystals may indicate necrosis or important tissue degeneration. The magnesium ammonia phosphate crystals are related to infections by urease-producing bacteria.

Calcium oxalate crystal dihydrate. Bright field microscopy¹

Cylinders

They are exclusively renal elements composed of proteins and molded mainly in the distal tubules of the kidneys. For this reason, all the particles that are contained inside come from the kidneys. Healthy individuals, especially after strenuous exercise, fever or use of diuretics, may have a small number of cylinders, usually hyaline.

The cylinders retain the contents of the renal tubules at the moment of their formation, constituting true “biopsies”. When in conjunction with other findings of urinary sediment and biochemical examination of urine, they function as biomarkers of the site of the kidney injury (glomerular, tubular or interstitial), of the nature of the injury (functional or structural) and even of prognosis.

In kidney diseases, they are present in large quantities and in different forms, according to the place of their formation. Cylinders can be present in different diseases: as hematic (intrinsic kidney disease), leukocytes (pyelonephritis), epithelial cells (lesions in the renal tubules), granular (glomerular or tubular kidney disease and some physiological situations) and brain (kidney failure, transplant rejection, acute kidney disease and urinary flow stasis).

Leukocyte cylinder in bright field. Bright field microscopy¹

Bacteria

Suspected urinary tract infection can occur if bacteria are present in samples recently obtained by medium-jet collection, particularly if numerous leukocytes are also present.

Normally the urine is free of bacteria, but if the sample is not collected under the right conditions, contamination can occur. Especially in women, bacteria and leukocytes in the urine may be the result of contamination with vaginal secretions.

In urinary tract infections with kidney involvement, in addition to leukocytes and bacteria, leukocyte cylinders and even cylinders containing bacteria can be observed.

Bacteria (Gram-negative bacilli) forming filaments and spheroplasts. Phase contrast microscopy (A) and Gram staining (B) ¹

Parasites

The Trichomonas vaginalis is a parasitic most frequently found in urine samples. Because it is a flagellated protozoan, it is easily identified by its rapid and irregular movement through the blade. However, when it does not move, it is very difficult to distinguish it from a leukocyte.

The finding in the urine generally indicates contamination by genital secretions, being a frequent cause of vaginitis and urethritis. Some other parasites can also be found, usually the result of fecal contamination.

Sedimentoscopy” refers to the microscopic analysis of urine sediment. This process is essential in clinical diagnostics, as it helps in identifying various cellular elements, crystals, and other substances in urine that can indicate different health conditions. The findings of a sedimentoscopy are often presented in a tabular format for clarity and ease of interpretation.

Here’s an example of how the findings might be presented in a table:

This table includes basic elements found in urine sediment, their descriptions, and what their presence might signify in terms of health conditions. The actual table used in a clinical setting would depend on the specific tests performed and the details required by the healthcare provider.