Urine Analysis: Part 4 – Urine Physical Examination, and Interpretation

Urine Analysis

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

Precautions

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

Physical Character:

Color

1. 1. The yellow color of the urine is due to pigment, which is called urochrome and is produced as a product of endogenous metabolism.
   2. Color intensity depends upon the concentration of the urine.
   3. Concentrated urine is darker in color.
   4. The pale yellow to light color is due to diluted urine.
   5. Yellow to amber color is due to urochromes, which are derivatives of urobilin, the end product of bilirubin degradation.
   6. Yellowish-brown to green color is due to bile pigments oxidation.
      1. While the blue/green color is due to pseudomonas infection.
   7. Blue urine color is due to the intake medication of methocarbamol, methylene blue, and amitryptiline.
   8. Red and brown after standing are due to porphyrins.
   9. 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 blood chemical test positive

   10. 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.
   11. In the case of malignant melanoma where melanogen oxidizes in the air to melanin.
   12. Drugs and some foods like beets may change the urine color.
   13. If urine shows large foam on shaking, it indicates an increased amount of protein in the urine.
       

       Urine color	Etiology for the color
       Pale yellow to light	Normal color
       Pale yellow	Polyuria, Diabetes inspidus, and Mellitus
       Dark  yellow and dark color	Concentrated urine Bilirubin Urobilin Biliverdin
       Yellow to amber	Urobilin Bilirubin Biliverdin
       Amber orange	Bilirubin, nitrofurantoin, and pyridium
       Yellow-brown or yellow-green	Bilirubin oxidized to biliverdin.
       Yellowish-brown to green	Bile pigments Bacteria (pseudomonas)
       Red and brown after keeping the urine	Porphyrins
       Redish brown in fresh urine	Hemoglobin and red blood cells Myoglobin Porphobilinogen Porphyrins
       Pink to red	RBCs Hemoglobin Myoglobin Beets, Rifampicin Menstrual contamination
       Brownish-black color	Alkaptonuria
       Changing color	Some of the drugs
       Green	Pseudomonas infection Biliverdin
       Brown-black	RBCs oxidized to methemoglobin. Melanin Homogentisic acid Metronidazole Methyldopa

       

       Urine colors in various conditions

       Urine color	Pathological causes	Nonpathological causes
       Red or reddish-brown	Hemoglobin, RBCs, Myoglobin, porphyrins	Drugs and dye, beets, rhubarb, senna
       Green	Biliverdin, bacteria (pseudomonas)	Vitamins, diuretics, psychoactive drugs
       Blue or blue-green	None	Urinary germicide, diuretics
       Orange	Bile pigments	Drugs like pyridium, phenothiazine
       Yellow-orange or yellow-brown	Bilirubin, Urobilin, dehydration, fever	Carrots, riboflavin, nitrofurantoin
       Black or brownish-black	Urobilin. melanin, methemoglobin	Iron preparations, levodopa
       Milky or opalescent	Bacteria and not cleared by acid, fat globules (lipiduria)

Odor

1. 1. Odor has little value in the diagnosis of various possibilities.
   2. 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.
   3. The characteristic pungent odor in fresh urine is due to volatile aromatic acids.
   4. Urinary tract infection gives a noxious, fecal smell, and it is unpleasant to smell.
   5. Diabetic urine often smells fruity as a result of ketones.
   6. Ingestion of onions, garlic, and asparagus can cause an unusual or pungent odor.
   7. Maple syrup odor is seen in maple syrup disease.
   8. A bleach-like smell is seen in contamination.
   9. The mousy odor is seen in phenylketonuria.
      

      Odor	The reason for that odor
      Faint aromatic (fresh urine)	Due to ammonia
      Strong, unpleasant odor	Bacterial infection
      Sweety or fruity odor	Diabetes mellitus ketone bodies
      Maple syrup odor	Maple syrup disease
      Unusual pungent odor	Ingestion of onions, garlic, and asparagus
      Mousy odor	Phenylketonuria
      Sweet smell	Malnutrition, vomiting, and diarrhea

Clarity

1. 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 degree of clarity (cloudiness)	Criteria
      Clear	No visible particulate material is seen.
      Hazy	Can see visible particulate material Can read the newspaper
      Cloudy	Can see the newspaper, but the words are distorted or not clear.
      Turbid	Can not see the newspaper through the urine tube

   3. Turbidity generally is due to gross bacteriuria.
      1. In alkaline urine, turbidity is due to amorphous phosphates and carbonates.
      2. 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 the 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:
      

      Normally found in the urine	Pathologic causes
      Amorphous phosphate	Amorphous urates
      Amorphous urates	Abnormal crystalluria like cysteine, tyrosine
      Presence of normal crystals	RBCs, WBCs, fat cast
      Mucus	Epithelial cells like renal transitional cells
      Bacteria	Bacteria in fresh urine
      Spermatozoa	Yeast, fungi, and parasites
      Prostatic fluids	Fecal material
      Epithelial cells (squamous cells)	Chyluria due to lymph is, although rare
      Contamination by powder, antiseptic	positive for malignant cells

Specific gravity

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

      Urine specific gravity formula

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

         Urine urinometer

      2. Refractometer. 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. The refractometer advantages are that it is needed two or three drops of urine.
            

            Urine Refractometer

      3. Chemical reagents strips. These are disposable colorimetric reagent strips. No instrument is needed.
      4. Automated instruments.
   5. Normal: 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
   6. After 12 hours of fluid restriction = >1.025
   7. Urine 24 hours = 1.015 to 1.025
   8. The diluted urine range is 1.000 to 1.010.
      1. Concentrated urine is 1.025 to 1.030.
   9. 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 consistent low specific gravity of 1.010 is known as isosthenuria. It is seen in chronic renal disease, where the capacity of concentrating urine is lost.
   10. High specific gravity urine (hypersthenuria) is seen in:
       1. Diabetes mellitus.
       2. Congestive heart failure.
       3. Dehydration due to sweating, fever, and vomiting or diarrhea.
       4. Adrenal insufficiency.
       5. Liver disease.Nephrosis.

pH

1. 1. Lungs and the kidneys are major regulators of the acid-base balance of the body.
      

      Urine pH control

   2. Urine pH must be performed on a fresh urine sample because the urine tends to change the pH on standing.
   3. The first-morning sample shows a pH of 5 to 6.
      1. After the meal may have alkaline pH.
   4. 4.6 to 7.0, and the average is 6.0
   5. pH depends upon the diet.
   6. 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.
   7. The acidity of urine is seen in:
      1. Systemic acidosis in diabetes mellitus.
      2. Renal tubular acidosis.
   8. 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. Medication like sodium citrate and sodium bicarbonate will reduce pH.
      5. Fanconi’s syndrome is congenital generalized aminoaciduria due to defective proximal tubular dysfunction.

1. The Effects of chemical used on urine	Possible cause of the turbidity
   Acidic urine	Amorphous urates, uric acid, contrast media
   Alkaline  urine	Amorphous phosphates, carbonates
   Solubility on heating the urine	Uric acid crystals and amorphous urates
   Insoluble in dilute acetic acid	Bacteria, yeast, WBCs, spermatozoa
   Solubility in dilute acetic acid	Amorphous phosphate, carbonates, and RBCs
   Solubility in ether	Lipids, lymph fluid

Osmolality (Osmolarity)

1. 1. Definition: 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.
      1. Osmolarity is the number of solute particles in one liter of the solvent.
      2. Osmolality is the number of solute particles in one Kg of solvent.
      3. The unit of the osmolarity is Osm/L.
      4. The difference in the dilute solution is negligible.
      5. Osmolality is preferred over osmolarity because it is higher.
      6. When evaluating the ability of kidneys concentration, Na+, K+, and Urea are important. All these three contribute to the osmolarity of the urine.
      7. Example: Osmolal solution of the Glucose is 180 g dissolved in 1 Kg of solvent.
         1. 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).
      8. 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.
      9. 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. 1. The urine volume depends on the amount of water excreted by the kidneys.
   2. The volume of the urine depends upon:
      1. The fluid  (water) intake.
      2. Fluid (water) loss from the 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:
      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’s 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, 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.

Age	Normal volume
Newborn
1 to 2 days	30 to 60 mL/24 hours
Infant
3 to 10 days	100 to 300 mL/24 hours
60 to 365 days	400 to 500 mL/24hours
Child
1 to 3 years	500 to 600 mL/24 hours
8 to 14 years	800 o 1400 mL/24 hours
Adult
Male	800 to 1800 mL/24 hours
Female	600 to 1600 mL/24 hours
Elderly	250 to 2400 mL/24 hours

 

Clinical type of proteinuria	Etiology of proteinuria
Prerenal	I/V hemolysis Muscle injury Multiple myeloma Severe infections
Renal	Immune complex disease Amyloidosis Dehydration Hypertension Pre-eclampsia Toxic drugs Diabetic nephropathy Strenuous exercise Orthostatic proteinuria
Postrenal	Lower urinary tract infection Vaginal secretion Prostatic fluid /spermatozoa Menstrual contamination Injury/trauma
Tubular disorders	Severe viral infections Toxic injury. Heavy metal intake Fanconi’s syndrome

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

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