Hyaline Casts in Urine : Morphology And Clinical Significance

Hyaline Casts in Urine : Morphology And Clinical Significance

Urinary casts are tiny cylindrical, tube-shaped particles that can be found during the microscopic examination of urine. Casts are the only elements found in the urinary sediment that are unique to the kidney. Tamm-Horsfall mucoprotein (uromodulin) secreted by renal tubular epithelial cells is believed to form the basic matrix of all casts. Any elements present in the tubular filtrate, including cells, bacteria, granules, pigments and crystals may become embedded to the cast matrix to form variety of casts. Different types of casts found in urine sediment represent different physiologic and clinical conditions.Urinary casts can be divided into two main categories; Cellular casts and Acellular casts. Hyaline cast is a type of acellular cast.

Acellular Casts	Cellular Casts
Hyaline Casts	RBC Casts
Granular Casts	WBC Casts
Waxy Casts	Bacterial Casts
Fatty Casts	Epithelial Cell Casts

Hyaline Casts

Hyaline casts are the most commonly occurring casts in urine. They are composed almost entirely of Tamm-Horsfall mucoprotein. They have smooth texture and a very low refractive index, similar to that of urine in which they are suspended. They appear colorless and almost invisible under bright field microscope and have parallel sides and rounded ends. Occasional granular inclusions may be present in the matrix.

Clinical Significance

The presence of 0-2 hyaline casts per LPF is considered normal. Some physiological and pathological conditions are associated with increased amount of hyaline casts in urine.

Physiological Causes

Increased amounts of hyaline casts are usually associated with:

• Physical exercise
• Physiologic dehydration
• Exposure to heat
• Emotional stress

Pathological Causes

Pathologically, increased amount of hyaline casts are usually associated with

• Acute glomerulonephritis
• Pyelonephritis
• Chronic renal disease
• Congestive heart failure
• Meningitis
• Diabetic nephropathy

Heat and Acetic Acid Test for Proteinuria: Principle and Procedure

Heat and Acetic Acid Test for Proteinuria: Principle and Procedure

Most plasma proteins are too large to pass through the glomeruli of the kidney. The small amount of protein which does filter through is normally reabsorbed back into the blood by the kidney tubules. Only trace amounts of protein (less than 150 mg per 24 h) can therefore be found in normal urine. These proteins include Tamm-horsfall protein (Maximum-40%), Albumin (20%), Immunoglobulins, Hormones, Enzymes and Mucopolysaccharides.

When more than trace amounts of protein are found in urine, this is termed proteinuria. Detection of proteinuria is an important indicator of renal disease because protein has a very low maximal tubular rate of reabsorption. The following methods are used to test for proteinuria:

Qualitative Tests:

1. Heat and acetic acid test
2. Sulphosalicyclic acid test
3. Hellers nitric acid test

Quantitative Tests:

1. Esbach’s method
2. Aufrecht’s method

Other tests:

1. Protein reagent strip test
2. Biuret test
3. Urine protein electrophoresis

Heat and acetic acid test

Principle:

This test is based on the principle that proteins get precipitated when boiled in an acidic medium.

Procedure:

1. Take 5-10ml clear urine in a test tube.
2. Boil the upper portion over a flame.
3. Compare the heated part with the lower part. Cloudiness or turbidity indicates the presence of either proteins or phosphates/carbonates.
4. Add 2-4 drops of 10% glacial acetic acid and boil the upper portion again.
5. If turbidity is still present, protein is present in urine. If turbidity disappears, that is due to phosphates or carbonates present in urine.

Result and Interpretation:

Grade the turbidity as follows:

• Negative : No cloudiness
• Trace: Barely visible cloudiness.
• 1+ : definite cloud without granular flocculation
• 2+ : heavy and granular cloud without granular flocculation
• 3+ : densed cloud with marked flocculation.
• 4+ : thick curdy precipitation and coagulation

References

1. Sood R. Concise book of Medical Laboratory Technology. Jaypee Brothers Pvt. Limited; 2015.
2. Cheesbrough M. Medical laboratory manual for tropical countries. M. Cheesbrough, 14 Bevills Close, Doddington, Cambridgeshire, PE15 OTT.; 1981.

Sulphosalicylic Acid Test for Proteinuria: Principle and Procedure

Most plasma proteins are too large to pass through the glomeruli of the kidney. The small amount of protein which does filter through is normally reabsorbed back into the blood by the kidney tubules. Only trace amounts of protein (less than 150 mg per 24 h) can therefore be found in normal urine. These proteins include Tamm-horsfall protein (Maximum-40%), Albumin (20%), Immunoglobulins, Hormones, Enzymes and Mucopolysaccharides.

When more than trace amounts of protein are found in urine, this is termed proteinuria. Detection of proteinuria is an important indicator of renal disease because protein has a very low maximal tubular rate of reabsorption. The following methods are used to test for proteinuria:

• Qualitative Tests:
  Heat and acetic acid test
  Sulphosalicyclic acid test
  Hellers nitric acid test
• Quantitative Tests:
  Esbach’s method
  Aufrecht’s method
• Other tests:
  Protein reagent strip test
  Biuret test
  Urine protein electrophoresis

Sulphosalicylic Acid Test

Principle

Proteins are precipitated by 5-sulphosalicylic acid. Any resulting turbidity will give an estimation of the amount of protein present in the urine which can be subjectively quantitated visually or more precisely quantitated using photometry. Cells and casts in the urine must be removed by centrifuging before carrying out the test. The test can detect albumin, hemoglobin, myoglobin, and Bence Jones proteins.

Requirements

• Specimen:
  Random urine
• Apparatus:
  Centrifuge, general purpose
  Graduated pipettes/micropipettes
  Measuring Cylinder
  Test Tubes
  pH paper/ pH meter
• Reagents:
  5-sulphosalicylic acid solution-3%
  Glacial acetic acid-10%

Procedure

1. Check the pH of a portion of urine, if it is alkaline or neutral, add 10% acetic acid solution, drop by drop, until it is just acidic (about pH 6).
2. If the urine is cloudy, filter or centrifuge the urine (5 minutes, 2000-3000 rpm).
3. Take 2ml clear urine in a test tube.
4. Add 2 ml 5-sulphosalicylic acid solution and mix. Do not shake. Examine for turbidity against a dark background.

Result and Interpretation

Grade the turbidity as follows:

Negative : No cloudiness
Trace: Faint turbidity.
1+ : definite turbidity
2+ : Heavy turbidity but no flocculation
3+ : Heavy turbidity with light flocculation.
4+ : Heavy turbidity with heavy flocculation.

Note:

Normal urine doesn’t contain detectable protein by this method. A false positive result may be obtained if the patient is receiving tolbutamide, penicillin and some other drugs. High concentration of urates in the urine may cause a false positive result due to precipitation of urate in an acidic urine.

References

1. World Health Organization, 1986. Methods recommended for essential clinical chemical and haematological tests for intermediate hospital laboratories/Working Group on Assessment of Clinical Technologies. In Methods recommended for essential clinical chemical and haematological tests for intermediate hospital laboratories/Working Group on Assessment of Clinical Technologies.
2. Ridley J.W. (2018) Procedures for Complete Urinalysis/Confirmation Testing. In: Fundamentals of the Study of Urine and Body Fluids. Springer, Cham. https://doi.org/10.1007/978-3-319-78417-5_10
3. Cheesbrough, M., 1981. Medical laboratory manual for tropical countries (Vol. 1). M. Cheesbrough, 14 Bevills Close, Doddington, Cambridgeshire, PE15 OTT..