Hyaline Casts in Urine - Causes, Normal range and High levels Significance, Microscopic images

One of the things being checked in a routine urinary exam is the presence of a cast in urine. the urinary cast is a minute cluster of particles in urine, which usually consists of fatty bodies, bacteria, and cells, encased in a protein matrix.

The presence of a cast is one of the indicators used to check for renal status. It is a parameter used to identify the functions of the kidneys. One of the common urinary cast types is a Hyaline cast.

The kidneys and formation of the cast in urine

The kidneys are bean-shaped organs inside the abdomen.
There are two kidneys and they are on either side of the lower section of the spine.
Kidneys have nephrons, which serve as the filtering units.
There are millions of nephrons and together they work hand in hand to do the filtration functions.
Each nephron is made of a glomerulus (a ball-shaped network of blood vessels involved in the generation of urine).
It also has kidney tubules, which reabsorb and adjust urine composition according to the needs of the body.
The formation of the cast takes place in the kidney tubules’ terminal segment. Its main components are collecting ducts and distal convoluted tubules.
It originates from the precipitation of Tamm–Horsfall protein released by the epithelial tubule cells.

If Tamm–Horsfall protein is aggravated, it can attract the attachment of other tubular particles such as:

Albumin
Bile
Hemoglobin
Cells
Immunoglobulins.

Urinary casts will eventually form and will dislodge from the tubular lumen. the casts will then move through the urinary tract and eventually be expelled in the urine.

Based on the content, urinary casts can be classed into cellular and non-cellular casts.

A cast is cellular if it consists of red blood cells (RBCs), renal tubular epithelial casts, and white blood cell (WBC) casts. On the other hand, a cast is non-cellular if it consists of the granular, waxy cast, fatty casts, and hyaline casts.

Hyaline casts in urine – what do they indicate?

Hyaline casts are regarded to be a general finding— they can be detected in both healthy persons as well as those having pathological disorders.

The development of hyaline casts often suggests a diminished or slow urine flow, which might be a result of excessive exercise, use of diuretic drugs, fever, or acute vomiting.

In conjunction with the other examination findings, significant quantities of hyaline casts may suggest kidney damage due to decreased flow of blood into the kidneys.

Hyaline casts in urine six casts and there explaination — Source: researchgate.net

Are hyaline casts normal in urine or do they suggest danger?

Casts in the urine are typically thought to be an unusual discovery. Hyaline casts can, however, be found in the urine of healthy people in modest amounts (between 0 and 2 per low power field of the microscope), which does not always mean that a significant ailment like renal disease is present.

They are generally not seen to be dangerous discoveries. In fact, the only casts that should be seen in urine in the absence of kidney or renal disease are hyaline casts.

Other urinary casts, as opposed to hyaline casts, are typically linked to renal illness.

Epithelial cells in urine are associated with extreme damage and death of tubule cells.
Red blood cell casts frequently signify microscopic bleeding within the kidneys or glomerulonephritis, which is an injury to the glomerulus.
White blood cell casts are frequently linked to inflammatory processes or kidney infections, such as pyelonephritis.
Fatty casts in the urine are frequently found in people with nephrotic syndrome, which results in excessive protein in urine or proteinuria, tissue edema, high level of blood cholesterol, and low blood protein levels.

What causes Hyaline casts?

In the tubular lumen of the kidney, aggregated Tamm-Horsfall protein makes up hyaline casts.
Acidic urine, slow or diminished flow, or extremely concentrated increases the precipitation of Tamm-Horsfall protein.
Therefore, it is possible to find more hyaline casts in patients with acute vomiting or fever, after engaging in vigorous exercise, or after using specific types of diuretics.
Hyaline casts can also show up on their own or in combination with other cast forms in some clinical circumstances, such as acute renal injury.

How do you Diagnose Hyaline casts?

Abundant Hyaline Casts under bright Field microscopy(A) Unmarked (B)marked for better visualization. — Abundant Hyaline Casts under bright Field microscopy
(A) Unmarked (B) marked for better visualization
Source: renalfellow.org

Urinary sediment microscopy, carried out as part of the urine analysis, can be used to diagnose hyaline casts.

In this laboratory testing, the urine sample is put into a centrifuge to thoroughly separate the fluid from the urine sediment, which includes suspended particles like casts, cells, and pathogenic bacteria.

The urine sediment is then deposited in a small droplet on a glass slide for microscopical analysis.

Hyaline casts show transparent, small tubule-shaped particles under bright field microscopy. Because of their low refractive index or the absence of contrast between hyaline casts and their surrounding urine they are frequently easily overlooked.

Hyaline castings are typically easier to identify with the use of the following:

Staining
Decreasing or dimming of lighting
Phase contrast microscopy

They must be separated from mucus strands since they are very difficult to identify in moist urine preparations. Hyaline casts often have blunted edges, clear margins, and parallel sides, whereas mucus strands have more varied sizes and uneven margins.

Hyaline casts in urine sediment samples must be seen in reduced lighting conditions. By decreasing the substage condenser, lighting can be decreased.

Hyaline casts can be seen much more clearly when employing phase contrast microscopy, which is not a feature of regular microscopes.

If fat adheres to the matrix of the protein matrix that makes up the hyaline cast or if debris from deteriorating cells is present inside the cast matrix, they become more noticeable under ordinary light microscopy.

It should be noted that hyaline casts are still called hyaline casts and not fatty casts when fat droplets adhere to them. In order to more accurately distinguish organisms and particles, phase contrast microscopy is used.

It is an optical microscopy technique that increases the contrast between two media that have the same refractive index.

How do you treat hyaline casts?

Hyaline casts are not always seen to be odd in healthy people, therefore they might not even need treatment. However, depending on the precise reason for the decreased renal function, treatment may be required if hyaline casts are seen in people with kidney disease.

Treatment options include the following:

For acute kidney injury, for instance, can include avoiding drugs that might impair kidney function
Making sure the patient is well hydrated with intravenous fluid infusion.
Addressing the particular cause of kidney damage.

Disclaimer: It is important to consult with a healthcare provider if you have any concerns about hyaline casts in your urine. They can provide a proper diagnosis and recommend a treatment plan if necessary.

Frequently asked Questions

Q: My hyaline casts in urine are 3-5 and sometimes 11-20 ? What does it mean ?

There are several potential causes of increased hyaline casts in the urine, including:

1. Dehydration (most common – so don’t panic)
2. Elevated albumin concentration
3. Kidney infections or inflammation (glomerulonephritis)
4. Certain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs)
5. Chronic kidney disease
6. Acute tubular necrosis, which is a type of kidney injury
7. Toxins or poisons that can damage the kidneys
8. Systemic lupus erythematosus (SLE), an autoimmune disorder that can affect the kidneys