Urine and Urine Sediment Images (identification) questions are reversed

Stain: Sedistain Cells are identified largely on the basis of size. RBC are the smallest cells and are often slightly orange. WBC are slightly larger than RBC and have pale, slightly granular cytoplasm. WBC nuclei may or may not stain with Sedistain Transitional epithelial cells vary considerably in size, but tend to be large and round with abundant granular cytoplasm surrounding a round nucleus. Renal epithelial cells are VERY difficult to distinguish from small transitional cells, but should be slightly larger than WBC and have a round nucleus that fills most of the cytoplasm. The most reliable way to identify renal epithelial cells is by air‐drying a smear of urine sediment and staining it with a Romanovsky type of stain such as DifQuick. Squamous cells are the largest cells that can be found in urine sediment. They are flat and plate‐like with angular sides. A nucleus, if present, may be very small.Cells in Urine Sediment

Cells in Urine Sediment

This schematic illustrates the types of a cast that can occur. Hyaline casts are composed of pure mucoprotein. Cellular and granular casts occur when cells become embedded in the mucoprotein. This can occur due to infiltration of WBC (inflammation), sloughing of renal epithelial cells (tubular damage), or hemorrhage. The presence of casts indicates renal disease. Proteinuria due to glomerular disease can lead to hyaline cast formation, while renal tubular damage or inflammation within the renal tubules can lead to other forms of casts.

Cellular Cast Formation

Cast Stain: H+E This histologic section illustrates formation of a cast within a renal tubule. Casts are elongated, cylindrical structures that form due to Tamm‐Horsfall mucoprotein "congealing" within the distal tubules and collecting ducts. Mechanisms responsible for the precipitation of this material are not understood but significant proteinuria seems to be one trigger. The result of this precipitation is a model or "cast" of these structures

Identify

Hyaline casts are translucent and difficult to detect when unstained and in this image the hyaline cast is outlined by a series of arrows. With unstained sediment, it is important to lower the condenser and/or close the iris diaphragm of the microscope to increase contrast and help increase the visibility of these structures. It is much easier to visualize granular casts which contain debris derived from either renal tubular epithelial cells or inflammatory cells (WBCs).

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RBCs and Squamous Cells image Stain: unstained A number of angular squamous cells are present. The cytoplasm of squamous cells tends to be clear and homogeneous. The edges of these flat cells sometimes fold over upon themselves. Moderate numbers of RBC and 2 round transitional cells are also present. RBC have smooth, homogeneous, slightly orange cytoplasm. Transitional cells have cytoplasm that is slightly grainy and relatively large round nuclei.

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Squamous cells image This slide of unstained urine sediment shows 2 large flat squamous cells and 3 WBCs (arrow). Notice the small size, lobular nucleus, and grainy cytoplasm of the WBCs. In older samples, the WBC nucleus may degenerate and not be obvious.

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Stain: New Methylene Blue Several RBC can be found, some slightly purple. A few sperm, a single WBC, and a squamous cell are also present. Sperm are commonly found in urine from intact male animals or recently bred females.

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Stain: Sedistain This is an example of a hyaline cast. Note the cigar shape with blunt, rounded ends. It is composed of a relatively smooth, homogeneous material. These casts are translucent and difficult to detect when unstained. If hyaline casts are the predominant type of cast present, it is most often due to significant proteinuria as a result of glomerular disease.

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Stain: unstained Shows several WBC (arrows) and a few RBC. Note the difference in size and texture of the cytoplasm.

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Stain: unstained This slide shows moderate numbers of fat droplets. Fat droplets closely resemble RBC. Both RBC and fat droplets are round and slightly refractile with a smooth surface. Fat droplets, however, often vary in size and float to a different plane of focus. This is most obvious by focusing up and down and determining that the droplets are out of focus when the remainder of the elements are in sharp focus.

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Stain: unstained numerous bacterial rods. A single transitional cell is also present. Bacterial cocci cannot be identified urine sediment unless they form chains. Particles of granular debris from ruptured cells (etc) can be easily mistaken for cocci. Small numbers of bacteria are often present in voided urine due to contamination from the lower urogenital tract.

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Transitional cell cluster Unstained urine sediment ‐ A cluster of transitional cells is present in the center of the field. These cells are much larger than the RBC and WBC present in the background. They have granular cytoplasm and a centrally located, round nucleus. The WBCs also have grainy cytoplasm and can occur in clusters but are smaller than the transitional cells.

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WBCs and caudate shaped transitional cells Stain: Sedistain Three caudate epithelial cells are present in the center of the field. These elongated, "kite‐shaped" cells are thought to arise from the renal pelvis, but have no known clinical significance. Multiple WBC and single, slightly larger, transitional cell can also be seen.

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As WBC or epithelial cells within the cast deteriorate the residual debris remains in the mucoprotein resulting in a granular cast. Over time, the small debris within a granular cast will undergo further degradation resulting in a waxy cast. Waxy casts are uncommon, but when present indicate chronic disease. RBCs do not typically result in granular casts because their cytoplasm is not particularly grainy, so over time a RBC cast will transform into a hemoglobin cast, not a granular cast.

Transformation of Cellular Cast

Urine specific gravity can also be determined by using a urinometer. To use this, room temperature urine is placed in a cylinder and then a calibrated floatation devise is placed in the urine. There is a calibrated specific gravity scale on the stem of the float. The float will sink to a variable degree dependent on the specific gravity. The reading is taken from the scale at the level of the fluid meniscus. The major drawback of this method is that it requires a large volume of urine and is somewhat messy to perform.

Urine SG via midget Urinometer

Refractometer Specific gravity provides an indication of urine concentration. open door...drop of urine...close door...hold like a telescope. You look into the view port on the left side while allowing light to shine on the drop of urine.

Urine Specific Gravity measured normally via

Normal urine is pale yellow to amber in color. This color variation occurs due to variation in urine concentration. More diluted ....lighter in color color changes...can signal presence of abnormal substances : hemoglobin or myoglobin ( red to red brown)

Urine appearance

Typically three calibrated scales are present. (right side) indicates the protein level within serum or plasma. The other two scales are used to determine urine specific gravity. ---> Protein or specific gravity readings are taken at the interface between light and dark areas. The specific gravity scale on the left is used for urine from most domestic species. Feline urine refracts light in a slightly different manner, therefore a separate scale is needed (middle scale). It is important to specifically use a veterinary refractometer. Most refractometers are calibrated for urine and serum at room temperature. Specific gravity will increase when urine is cold.

Veterinary Refractometer Scales