Urinary casts are one of the constituents often looked for when a microscopic examination of urine sediment when a urinalysis is done. They can often be hard to find in a regular brightfield microscope without staining, but they can be extremely helpful in investigation various types of pathology that may be occurring in the kidneys. A urinalysis (or UA) is an array of tests performed on urine and one of the most common methods of medical diagnosis. ...
Casts are formed through the process of solidification of materials in the tubules of the nephrons, or working units of the kidneys. Later, the material is then flushed out of the kidney upon the production of more urine, leaving a small solidified microscopic cylinder that can also contain whatever other materials that might be within the tubules of the kidneys at the time of the cast's formation. Nephron of the kidney A nephron is the basic structural and functional unit of the kidney. ...
Human kidneys viewed from behind with spine removed The kidneys are bean-shaped excretory organs in vertebrates. ...
Urine is liquid waste excreted by the kidneys and is produced by the process of filtration. ...
The microscopic detection of various types of casts can often be a helpful diagnostic tool to help in understanding the nature of various types of renal disease.
There are an array of different types of casts that can be found in different urine sediments. Some of them might be classified as follows.
These casts are the most common type of cast, and often they can be found in normal urine samples, especially after vigorous exercise. Hyaline casts result from the solidification of Tamm-Horsfall protein, which is secreted by renal tubular cells and may be seen without significant or abnormal proteinuria.
Cellular casts are formed when either cells are conglutinated together in the kidneys and excreted, or are simply trapped through the precipitation of protein and the entrapment of cells as the process is occurring.
Types of Cellular Casts include the following:
White Blood Cell Casts
Also referred to as leukocyte casts, or pus casts. These are formed when a large number of white blood cells are present. The fact that they are together in a cast in urine sediment indicates that they have originated in the kidneys and not in the bladder or elsewhere. They might possibly indicate kidney infection or inflammation.
Epithelial Cell Casts
These casts result when the epithelial cells of the renal tubules are being excreted along with the casts. These rarer casts can in theory indicate a serious situation involving the possible breaking down of the lining of the renal tubules themselves.
Red Blood Cell Casts
These can possibly in theory result from bleeding within the kidneys, along with other types of kidney disease as well.
These are an aggregation of bacteria within a cast, and can indicate in theory a severe bacterial infection in the kidneys.
Granular casts can result either from the breakdown of cellular casts to a point where the cells that once were within them are no longer distinguishable, or they can result from the inclusion of aggregates of plasma proteins, fibrinogen, or immune complexes within the cast upon formation. They can be further divided into Coarse Granular and Fine Granular. The former represents the recent deposit of the cast whereas the latter indicates that the cast was in the tubules for a while before it was excreted.
These are often a result from the final degradation of cellular and granular casts. They can often be the result of severe renal failure or stasis.
These casts contain droplets of fat, and are the result of the inclusion of oval fat bodies and fat globules within the cast.
Casts can also include various pigments, drugs, or various crystals commonly found in urea, including urates, calcium oxalate, or sulfonamides. Calcium oxalate is a chemical compound that forms needle-shaped crystals. ...
Sulfonamides, also known as sulfa drugs, are synthetic antimicrobial agents derived from sulfonic acid. ...
- Urine Casts - different types and what they mean.