All of the stable materials suspended in the urine are referred to as urine sediment. Microscopic urine sediment analysis is particularly useful for detecting kidney and urinary tract disease. Microscopic inspection of such findings can aid in the clarification of erroneous physical and chemical studies. The urine that has developed components comes from the skin, liver, lower genitourinary tract, and external contamination. RBCs, WBCs, epithelial cells, casts, bacteria, yeast, fungi, mucus, crystals, spermatozoa, and particles are among the substances involved. Since some of these elements have no medicinal relevance and others are considered natural unless they are found in large quantities, a urinary sediment analysis must provide both recognition and quantification of the elements present.
Preparation of the Urine Sediment
Since some of these components have little medicinal importance while others are deemed natural until they are found in high quantities, a urinary sediment analysis must provide both recognition and quantification of the elements present.
In a conical tube, a regular amount of urine, usually between 10 and 15 mL, is centrifuged. This gives you the right amount of material to get a representative sample of the ingredients in the specimen.
The amount of time the specimen is centrifuged can be associated with the speed of the centrifuge. The best volume of sediment that is less likely to damage the elements is generated by a five-minute centrifugal centrifugal force (RCF) of 400.
A standardized volume of urine and sediment will remain in the tube until decantation. Typically, volumes of 0.5 to 1.0 mL are used. The concentration factor is the number of sediments divided by the quantity of urine centrifuged. The concentration factor for sediments is used to quantify the number of elements present per mililiter which corresponds to the probability of identifying elements present in low concentrations.
Volume of Sediment Examined
The sediment volume placed on the microscope slide for each specimen should be constant. Using the traditional glass-slide method, the recommended volume is 20 uL (0.02 mL) filled with a 22 x 22 mm glass cover slip. Allowing the specimen to flow outside of the cover slip will result in the loss of heavy components like casts.
Examination of Urine Sediment
To comprehend, it is important to recognize both regular and uncommon constituents. Under the microscope, regular constituents are normally more prominent, and they must be marked such that the presence of the less visible but more significant irregular constituents is not obscured. The microscopic study can be performed in a consistent manner, with at least 10 fields being observed at low (10x) and high (40x) power levels. The slide is first studied under low force to detect casts and determine the general composition of the sediment. The setting is modified to high power as elements are found, such as casts that need to be identified.
Look for the following with the low-power (x10) objective:
- Casts. Check the whole region with uniform slides for the presence of casts. Look for casts along the four corners of the preparation, then in the middle, for conventional slides, so casts appear to roll to the edges of the cover glass.
- When you find a cast, switch to high power to label it.
- Casts are graded and reported based on the total number of people seen per low-power sector. If a single specimen contains more than one type of cast, classify and grade each type separately.
- Amorphous and crystallized materials In the same way that you can look for casts, look for these constructs.
- If normal crystals are present, they are recorded as few, moderate, or many per high-power area. Crystals, on the other hand, can be more visible at low strength.
- When abnormal crystals are present, they are rated based on the average amount seen per low-power area. Until abnormal crystals are identified, they must be verified by a chemical examination or a clinical history.
- Form, rather than height, is used to identify crystals. As a result, detection and identification require a combination of low-power and high-power observations.
- Epithelial cells (squamous epithelium): Report as few, mild, or many per low power field if these are present.
- Mucus (mucous threads): When easily seen or prominent under low power, these are reported as current. Phase-contrast microscopy makes them more visible.
With high-power (×40) objective, search for the following:
- Red blood cells. The average amount seen per high-power is used to grade and study. If you come across some irregular shapes, such as dysmorphic red cells, report them.
- White blood cells. The average number seen per high-power field is used to grade and report. Commonly, they are neutrophils (PMNs). Report any rare cell forms, such as lymphocytes or eosinophils, that are morphologically recognizable.
- Normal crystals. Each type of crystal observed should be identified and reported as few, small, or many per high-power region.
- Casts. Use high power to identify, but low power to grade.
- Epithelial cells: renal tubular, oval fat bodies (renal tubular cells with fat), and transitional. Estimate and record as few, moderate, or many per high-power sector where these are present.
- Miscellaneous. This group contains yeast, bacteria, trichomonads, and fat globules, as well as other cell types and other structures found in urine sediment. Where these are present, classify the cell or structure and record the number of cells or structures per high-power field as few, moderate, or more. Just report the presence of sperm in males. It is not recorded in normal urinalysis specimens from females because it is considered a contaminant.
CONSTITUENTS OF URINE SEDIMENT
Biological or chemical constituents make up the majority of urinary fluid. RBCs (erythrocytes), WBCs (leukocytes), epithelial cells, organic fat, casts, bacteria, yeast, fungi, parasites, and spermatozoa are all found in the biological portion of the sediment, also known as the ordered sediment. (The casts are long cylindrical structures that form as a fluid within the kidney tubule lumen solidifies.) More kidney disease or dysfunction, tumors, tumor or lesion, stone growth, and common bleeding problems, as well as the use of anticoagulants, are both biological components.
Hematuria is a reliable early indicator of renal disease. Chemical crystals and amorphous material make up the chemical component, which is also known as unorganized sediment. It is, on average, less essential than the portion of biology. However, several unusual crystals have pathological implications. Furthermore, the components of a crystalline or chemical substance are often so various that they seem to cover the most important parts, which must be carefully examined.
Several Urinary Crystals are described below.
|Uric Acid||Acid||Yellow-Brown||Aklali Soluble|
|Amorphous Urates||Acid||Brick Dust or Yellow||Alkali and heat|
|Calcium Oxalate||Acid/Neutral||Colorless||Oval on Dilute HCL|
|Amorphous Phosphates||Alkaline/Neutral||White-Colorless||Dilute acetic acid|
|Calcium Phosphate||Alkaline/Neutral||Colorless||Dilute Acetic acid|
|Triple Phosphate||Alkaline||Colorless||Dilute Acetic acid|
|Ammonium Biurate||Alkaline||Yellow-Brown||Acetic acid with heat|
|Calcium carbonate||Alkaline||Colorless||Gas from acetic acid|
|Cystine||Acid||Colorless||Ammonia, Dilute HCL|
|Leucine||Acid/Neutral||Yellow||Hot alkali or alcohol|
|Tyrosine||Acid/Neutral||Colorless-Yellow||Alkali or Heat|
|Bilirubin||Acid||Yellow||Acetic acid, HCl, Naoh|
|Radiographic dye||Acid||Colorless||10% NaoH|
Images of frequently found urine sediments
- Strasinger, S. K., & Di, L. M. S. (2014). Urinalysis and body fluids. Philadelphia: F.A. Davis Co.