Urine Analysis, Physical Examination

• These are the normal constituents and findings in normal urine.
• Routine urinalysis includes:
  1. Physical character.
  2. Chemical analysis.
  3. Microscopic examination.

Precautions for urine collection:

1. Urine must be analyzed within one hour of collection if held at room temperature.
2. Keep urine at 2 to 8°C if delayed >8 hours.
3. If urine is kept for a longer time, then it will get a false positive test, like nitrite will be positive.
4. Urea-producing organisms will degrade urea to ammonia and change the pH to alkaline.
5. Change in pH causes degeneration of cast and cell lysis.

Factors that will interfere with the urine analysis:

1. Certain foods will color the urine, like:
   1. Carrots will change their urine color to dark yellow.
   2. Beets may cause red color urine.
   3. Rhubarb will change its color to red or brown.
2. Asparagus produces a typical urine odor.
3. If you keep urine on the table, bacteria will change the urine pH, making it alkaline because of urea-splitting bacteria, and there is the production of ammonia.
4. Effect of the food on the urine pH:
   1. Eating citrus fruits, dairy products, and vegetables makes urine alkaline.
   2. A high protein diet and some foods (cranberries) make urine acidic.
   3. A high protein, a fat diet without the intake of carbohydrates also causes ketonuria.
5. When radiopaque contrast media is given to the patient will give false-positive urine protein for at least 3 days.
6. Females may have contamination from the vaginal secretions and show an increased number of WBCs.
7. Traumatic catheterization may cause hematuria and false RBCs in the urine.
8. Vaginal secretions contamination may cause false-positive leucocyte esterase.
9. False proteinuria is seen when urine is contaminated with vaginal secretions.
10. Urine culture gives false-positive results when contaminated with stool, vaginal secretions, and contaminated test tubes or hands and clothes.

Urine Physical examination:

Color

1. The color of the urine varies from colorless to black.
2. This variation in the color depends upon the following:
   1. Metabolic functions.
   2. Physical activity.
   3. Ingested food.
   4. Pathologic conditions.
3. Any change in the color needs to work up to find the cause.
4. The yellow color of the urine is due to pigment, which is called urochrome and is produced as endogenous metabolism.
5. Color intensity depends upon the concentration of the urine.
6. Concentrated urine is darker in color.
7. The pale yellow to light color is due to diluted urine.
8. The Yellow to amber color is due to urochromes, which are derivatives of urobilin, the end product of bilirubin degradation.
9. Yellowish-brown to green color is due to bile pigments oxidation.
   1. While the blue/green color is due to pseudomonas infection.
10. Blue urine color is due to the intake of medication of methocarbamol, methylene blue, and amitryptiline.
11. Red and brown after standing are due to porphyrins.
12. The reddish-brown color in the fresh sample is from hemoglobin and red blood cells.
    1. When RBCs are there for several hours in acidic urine, it will give rise to brown color due to oxidation of the methemoglobin.
    2. Hemoglobinuria shows red plasma due to hemolysis of the RBCs.
    3. Myoglobin is cleared from the plasma rapidly so that the plasma will be clear.

Urine physical examination, Urine positive for blood by chemical test

13. Urine is positive for blood by chemical tests, the brownish-black color ion is standing in the urine due to alkaptonuria because of the homogentisic acid excretion. In this case, the chemical blood tests will be negative.
14. In the case of malignant melanoma where melanogen oxidizes in the air to melanin.
15. Drugs and some foods like beets may change the urine color.
16. If urine shows large foam on shaking, it indicates an increased amount of protein in the urine.

Urine color variations:

Drugs that can change the color of the urine:

Urine color changes due to pathological and nonpathological conditions:

Various colors of the urine:

Urine physical examination, Various colors of the urine

Odor

1. This is not part of the urine analysis. It has no clinical significance.
2. Odor has little value in the diagnosis of various possibilities.
3. There is a typical ammonia smell.
   1. When urine is sometimes kept on the table, the odor of ammonia (NH 3) becomes more prominent.
   2. The breakdown of the urea by the bacteria in the urine is responsible for the ammonia smell.

4. The characteristic pungent odor in fresh urine is due to volatile aromatic acids.
5. Urinary tract infection gives a noxious, fecal smell, and it is unpleasant to smell.
6. Diabetic urine often smells fruity as a result of ketones.
7. Ingestion of onions, garlic, and asparagus can cause an unusual or pungent odor.
8. Maple syrup odor is seen in maple syrup disease.
9. A bleach-like smell is seen in the contamination.
10. The mousy odor is seen in phenylketonuria.

Various odors of the urine:

Clarity

1. Normal urine is clear and is judged against the light source.
2. The cloudiness of the urine specimen depends on pH and dissolved solids components like amorphous phosphates and carbonates.

Urine clarity variables:

Turbidity:

1. It is generally due to gross bacteriuria.
2. In alkaline urine, turbidity is due to amorphous phosphates and carbonates.
3. In acidic urine, turbidity is due to amorphous urates.
4. Smoky urine is due to hematuria.
5. In women, the epithelial cells and mucus may result in hazy urine.
6. Urine, when kept in the fridge, may become turbid without any pathology.
   1. In refrigerated urine, amorphous phosphates, carbonates, and urates give rise to thick turbidity.
7. Other turbidity causes are contamination with semen, feces, vaginal cream, talcum powder, and contrast media.
8. Turbidity may be seen in bacterial infection and the presence of RBCs and WBCs.

Common causes of cloudiness in the urine:

Various causes of turbidity:

Specific gravity

1. The kidneys’ ability to selectively absorb essential chemicals (electrolytes) and water from the glomerular filtrate is one of the most important body functions.
2. Specific gravity <1.003 is mostly not urine.

Definition of specific gravity:

1. This is the weight of 1 mL of urine in grams divided by 1 mL of water.

Urine specific gravity formula

2. This helps to give the state of hydration and dehydration.
3. This indicates the concentrating ability of the kidney.
4. The specific gravity of the urine can be measured by:
5. Urinometer (hydrometer):
   1. This consists of a weighted float attached to the scale that has been calibrated to urine-specific gravity.

1. 2. Refractometer:
   3.  This will determine the concentration of the dissolved particles in the urine. This will do by measuring the refractive index. This refractive index compares the velocity of the light in air with the velocity of light in the solution.
      1. 1. The refractometer’s advantages are that it needs two or three drops of urine.

Urine Refractometer

1. 4. Chemical reagents strips:
   5.  These are disposable colorimetric reagent strips. No instrument is needed.
   6. Automated instruments.

Normal urine specific gravity :

• 1.003 to 1.030 (1.005 to 1.030).

1. Most urine fall in the range of 1.015 to 1.025.
2. Newborn = 1.012
3. Infants = 1.002 to 1.006
4. Adult = 1.002 to 1.030

• After 12 hours of fluid restriction = >1.025
• Urine 24 hours = 1.015 to 1.025
• The diluted urine range is 1.000 to 1.010.
• Concentrated urine is 1.025 to 1.030.

Low specific gravity urine (hyposthenuria) is seen in:

1. Diabetes inspidus (not go above 1.001 to 1.003. ADH hormone is lacking.
2. Pyelonephritis.
3. Glomerulonephritis.
4. The consistently low specific gravity of 1.010 is known as isosthenuria. It is seen in chronic renal disease, where the capacity to concentrate urine is lost.

High specific gravity urine (hypersthenuria) is seen in:

1. Diabetes mellitus.
2. Congestive heart failure.
3. Dehydration due to sweating, fever, vomiting, or diarrhea.
4. Adrenal insufficiency.
5. Liver disease.Nephrosis.

pH

1. The lungs and the kidneys are major regulators of the acid-base balance of the body.
2. These two organs control the pH by the secretion of hydrogen ions in the form of ammonium ions, hydrogen phosphate, and weak organic acids.
3. These organs can maintain the pH by reabsorption of HCO3^– from the filtrate in the convoluted tubules.

Urine pH control by the lungs and kidneys

4. Urine pH must be performed on a fresh urine sample because the urine tends to change the pH on standing.
5. The first-morning sample shows a pH of 5 to 6.
   1. After the meal pH may be alkaline.
   2. Urine pH is 4.6 to 7.0, and the average is 6.0
6. pH depends upon the diet.
7. pH <7.0 is primarily caused by the phosphates, which are excreted as salts conjugated to Na⁺, K⁺, Ca⁺, and NH4⁺.
   1. Acidity also reflects the excretion of nonvolatile metabolic acids pyruvate, lactate, and citrate.
8. The acidity of urine is seen in the following:
   1. Systemic acidosis in diabetes mellitus.
   2. Renal tubular acidosis.
9. The alkaline urine (>7.0) is seen in:
   1. This is a normal reaction to the gastric acidity  (HCL) dumped into the duodenum and then to circulation.
   2. Urinary tract infection.
   3. Bacterial contamination of the urine.
   4. Medications like sodium citrate and sodium bicarbonate will reduce pH.
   5. Fanconi’s syndrome is congenital generalized aminoaciduria due to defective proximal tubular dysfunction.

Causes of acidic and alkaline urine:

Osmolality (Osmolarity)

1. Definition:
   1. Specific gravity depends on the number of particles present in a solution and the particles’ density, whereas osmolarity is affected only by the number of particles present.
   2. Osmolarity is the number of solute particles in one liter of the solvent.
   3. Osmolality is the number of solute particles in one Kg of solvent.
   4. The unit of osmolarity is Osm/L.
2. The difference in the dilute solution is negligible.
   1. Osmolality is preferred over osmolarity because it is higher.
   2. When evaluating the ability of kidneys concentration, Na⁺, K⁺, and Urea are important. All these three contribute to the osmolarity of the urine.
3. Example: Osmolal solution of the Glucose is 180 g dissolved in 1 Kg of solvent.
   1. The osmolar solution of glucose is 180 g dissolved in 1 Liter of solvent.
   2. The unit used in the laboratory is mOsm (milliosmole).
4. Use of the osmolality/osmolarity:
   1. It can monitor renal concentration ability for the course of renal disease.
   2. It can monitor fluid and electrolyte therapy.
   3. It can differentiate between hypernatremia and hyponatremia.
   4. It evaluates the secretion and renal response to ADH.
   5. There is a need to get the osmolarity of the serum and the urine.
5. Normal:
   1. 500 to 800 mOsm/ kg of water.
   2. Serum osmolarity = 275 to 300 mOsm.
   3. Urine osmolarity = 50 to 1400 mOsm.

Volume

1. The urine volume depends on the amount of water excreted by the kidneys.
2. The volume of the urine depends upon the following:
   1. The fluid  (water) intake.
   2. Fluid (water) loss from nonrenal sources.
   3. The amount of ADH secretion.
   4. Excretion of dissolved solids such as glucose or salts.
3. The urine volume excreted indicates the balance between fluid ingestion and water loss from the lungs, sweat, and intestine.
4. Normal urine volume:
   1. 1200 to 1500 mL/24 hours.
   2. The range of 600 to 2000 mL/24 hours may be considered normal.
   3. The average urine volume is 1200 ml.
5. Night urine volume is usually less in amount.
6. The ratio of day urine to night urine is  2: 1 to 4:1.
7. Nocturnal polyuria:
   1. There is increased urine at night. This may be seen in diabetes mellitus and diabetes inspidus.
   2. This may be seen as diuretics or intake of tea, coffee, or alcohol. These will suppress the ADH.
8. Polyuria is seen in:
   1. Diabetes mellitus.
   2. Diabetes inspidus.
   3. Chronic renal disease.
   4. In the case of acromegaly.
   5. In the case of myxedema.
9. Oliguria:
   1. There is a decrease in the normal daily urine volume.
      1. Anuria or oliguria, where urine volume is <200 mL/day.
   2. This is seen in dehydration due to vomiting, diarrhea, perspiration, or severe burn.
   3. Nephritis.
   4. Urinary tract obstruction.
   5. Acute renal failure.
   6. Oliguria may lead to anuria.
   7. Drugs that have diuretic effects are:
      1. Thiazides.
      2. Alcohol.
      3. Caffeine.
   8. The drugs which decrease the volume and are nephrotoxic are:
      1. Analgesics like salicylates.
      2. Antibiotics like neomycin, penicillin, and streptomycin.

Normal volume of the urine

Normal urine picture:

Questions and answers:

Note: Details are seen in Part 3, urine complete analysis.