In the hospital, the patients are asked to give a urine specimen for testing. These urine specimen are examined and tested within the ward or department, and others may be sent for a more searching examination to the bacteriological or biochemical laboratory. And a great deal can be learned from chemical testing of urine and this aids the physician in his diagnosis and also a guide to subsequent treatment.
During urine testing, there are points which you must observe and give a report on that; they are:
- The colour of the urine
- The specific gravity of the urine
- The urine odour
- The urine abnormalities
- Amount of the urine
- The deposits found in the urine
- The urine reaction during testing
Normal urine is described as being amber in colour. Depending on the amount of urine being passed, the colour in health may vary slightly. For example: If you drink a lot, the urine can be quite pale in colour, then in warm weather, if you are sweating and you are not drinking much fluid, the urine will be darker in colour. This is known as concentrated urine.
You should also know that the abnormalities that are present in urine may also cause a difference in colour of the urine. For example:
- Blood may give the urine a smokey colour if it is present in small amount and if present in large quantity or amount, it will actually make the urine appear red.
- Sufficient Bile pigment in the urine will make the urine look like strong tea and if there is a large amount of Bile pigment present in the urine, it will make the urine have a dark greenish colour.
AMOUNT OF URINE
The amount of urine passed by the average adult varies from time to time depending on the fluid intake and the amount of fluid lost by other routes, but the average is approximately 1100 to 1700 ml in twenty-four hours. In certain circumstances, there may be an appreciable increase or decrease in amount and special terms are used to describe these variables.
Polyuria : This is the term used to describe an increase above the normal limit in amount of urine passed; The urine is usually very pale in colour. It occurs in diabetes insipidus and uncontrolled diabetes mellitus.
Oliguria : This is the name given to the excretion of a decreased amount of urine passed in twenty-four hours and occurs in some heart diseases, acute fevers, acute nephritis and dehydration. The urine is usually much darker in colour than normal.
Anuria : This means that no urine is being passed at all and it also occurs in acute nephritis, crushing injuries and some other conditions.
SPECIFIC GRAVITY OF URINE
This is the term used to describe the weight of a substance as compared to the weight of an equal amount of distilled water. The specific gravity of urine is determined by using a urinometer. To take the specific gravity, the urine must be allowed to cool, the urinometer is placed into the urine glass and allowed to float freely in the urine. When reading the specific gravity, the eye should be level with the surface of the urine.
The normal specific gravity varies between 1010 and 1025, although it can show wide variations in healthy individuals depending on the amount of sweat lost and the amount of fluid taken into the body. For example: If an individual is drinking large quantities of fluid, the specific gravity will be low. On the other hand, if the person is sweating and the same time not taking much fluid, the urine will be concentrated and will be of high specific gravity.
DEPOSITS IN THE URINE
These are substances which are in solution when urine is passed but are deposited in the specimen glass when the urine has cooled or has been standing for some time. Some of the deposits which may be present in the urine are:
Phosphate : These deposits are usually of calcium and magnesium which form a white sediment at the bottom of the urine glass.
PUS : This forms a thick white ropey deposit and can be distinguished from phosphate using its ropey appearance when the urine is poured from one urine glass to another. The presence of pus also gives the urine a fishy offensive odour.
Urine has a characteristic odour, but if abnormalities are present, the odour caused by their presence can be quite distinctive:
Acetona : This gives the urine a distinctly sweet smell rather like the smell of a new mown hay. Acetone may be present in diabetes mellitus or starvation.
Pus : This gives the urine a fishy offensive odour and the urine has a ropey appearance.
Ammonia : When the urine smells of ammonia means that it has begun to decompose in the specimen glass.
This is tested usually in the ward by litmus paper. During the test, the following can be observed:
- Acid urine turns blue litmus paper red.
- Alkaline urine turns red litmus paper blue.
Urine is normally acid in reaction but it becomes alkaline when allowed to stand for some time. This is due to the decomposition of urea when exposed to atmospheric air and also causes the urine to smell like ammonia.
In health, the urine should be composed of the following substances only:
- 96 percent Water
- 2 percent Urea
The rest below make up the remaining 2 percent all together.
- percent Uric acid
- percent Creatinin
- percent Phosphates
- percent Sulphates
- percent Urates
The urine should be amber in colour, slightly acid in reaction with a specific gravity of 1010 to 1015 and approximately 1500 ml passed in twenty-four hours. Any deviation from these normal characteristics shows the presence of abnormalities.
Some diseases are characterised by the presence of abnormal substances in the urine. For example: In diabetes mellitus, sugar being present, in acute nephritis, albumin (protein) which may be present, in jaundice bile may be present.
Chemical tests can be carried out in the ward by the nurse to detect the presence of some types of abnormalities. The drug manufacturers have prepared equipment for ward testing of urine which is quick and reliable.
These tests will be described and one other alternative test for some of the abnormalities.
Urine for ward testing should be collected in a clean urine glass. The results found should be recorded and reported accurately.
Albumin Or Protein
If the urine is cloudy, it should be filtered and it should be acid in reaction.
With the equipment for this test, a chart is supplied with a colour scale and it is only by comparing the different colour scales that the correct answer can be determined.
Then dip the test end of the albustix into the urine and remove it immediately. Compare the colour of the dipped end with the colour scale which is a guide to the amount of albumin present. If the tip of the stick remains yellow, it means that there is no albumin. But if it changes in any way towards green, albumin is present. By comparing the colour of the albustix with the colour range on the chart provided, an estimate can be made of the amount of albumin present in the specimen.
A test tube should be three-quaters filled with urine and held by the lower end with the top over a bunsen flame. Boil the top inch of urine, if it becomes cloudy, a drop of acetic acid is added. If the cloud disappears, it has been due to the presence of phosphates and is of no significance. But if it remains, it indicates the presence of albumin.
This test merely indicates the presence of albumin but is no guide to the amount; therefore a quantitative test should be carried out.
Esbach Quantitative Test
Esbach urinometer is used for this test and is a glass tube calibrated from 0 to 7 and marked with the letters ‘U’ and ‘R’. Urine acid in reaction is filtered if cloudy and is poured into the tube to the marked ‘U’ and Esbach reagent added to the level ‘R’. A rubber stopper is placed in the opening of the tube and the tube inverted a few times.
The tube is then placed in its wooden container and allowed to stand for twenty-four hours without disturbance. The level of any white precipitate formed in the graduated tube shows the amount of albumin in grammes per 1000 millilitres of urine. If this figure is divided by 10, this will give a percentage amount.
If there is a large amount of albumin, that is over 0.4 grams percent, then the urine may be diluted with equal parts of water, reassessed and the result multiplied by two.
Sugar Or Glucose
This is a test which will indicate only the presence of sugar but not the amount.
Dip the test end of the clinistix in the urine and remove, leave for one minute then examine the tip of the stick; if no blue colour has appeared, there is no sugar present. If sugar or glucose is present, the tip of the clinistix will appear blue in colour.
This is a test which will estimate the amount of sugar present. Place 5 drops of urine into a test tube with the aid of the special dropper provided. Rinse the dropper and then add 10 drops of water to the urine. Drop in one clinitest tablet, effervescence occurs and the tube must not be moved for fifteen seconds after it has ceased. Shake the tube gently and compare the colour with the colour range on the chart scale.
The colour range is through a scale from blue, which is negative to dark green (0.25 percent) to lighter green (0.5 percent) to orange (1 percent) to a brownish colour (2 percent).
Benedict’s test drop 5 ml of Benedict reagent into a test tube and add 8 drops of urine. Boil this mixture vigorously for two minutes. If sugar is present, green, yellow or brick-red colour change occurs.
The changes from green to brick-red indicates increasing amounts of sugar. In percentage quantities they can be seen below:
Yellow = 1 percent
Deeper yellow = 1.5 percent
Orange = 2 percent
Brick-red = over 2 percent
Acetone or Ketone bodies
The term acetone is commonly used but it is to be appreciated that this term is also used when ketone bodies and diacetic acid are also meant.
Place an acetest tablet on a clean white sheet of paper then place one drop of urine on the tablet. Leave for thirty seconds then compare any colour change with the colour scale. A positive result varies from lavender to deep purple and may be recorded as a trace to strongly positive.
This is a test which determines the presence of blood but not necessarily the amount of blood present.
Place one drop of urine on a filter paper square and put one occultest tablet in the centre of the moist area, add two drops of water to the tablet and allow it to stand for two minutes. If after two minutes and a diffuse blue colour appears on the filter paper around the tablet, you should know that blood is present. The amount of blood is proportionate to the intensity of the colour and the speed with which it develops. If no blue colour appears, the test is negative.
Pour 1 inch of urine into a test tube, add 2 drops of tincture of guaicum to the urine then gently run some ozonic ether down the side of the test tube to form a layer on top of the mixture. A blue ring appears at the junction if blood is present.
You should know that ward testing for blood is not satisfactory and if it is thought that blood is present, the urine should be sent to the laboratory for microscopic examination of a centrifuged deposit.
With this test, a special test mat is provided and 5 drops of urine are placed on the mat, one ictotest reagent tablet is put in the centre of the moistened area. Flow 2 drops of water over the tablet. If bilirubin is present, a bluish-purple colour appears around the tablet in about thirty seconds. The amount of bilirubin present is determined by the speed and intensity of the reaction. If there is no colour change or only a pinkish colour then there is no bilirubin.
About an inch of urine is poured into each of two test tubes, several drops of tincture of iodine are added drop by drop to one of them. Shake the test tube with the iodine and urine and compare it with the control test tube. If a green colour develops, it is positive and contains bile pigment.
Vomiting, diarrhoea, gastric aspiration and some diseases may cause a fall in blood chloride; therefore a quantitative test for chloride in the urine can be of assistance in diagnosing salt depletion. It is to be appreciated that this is not a test to estimate the blood chloride level but merely a test to assess the amount of chloride either present or not in the urine. The amount of chloride normally present in the urine is 3 to 5 grams per litre, but this will depend on the volume of the urinary output.
Things required for the test
- Clean pipette
- Clean test tube
- 20 percent potassium chromate solution
- 2.9 percent silver nitrate solution
- Distilled water
Using the pipette, place 10 drops of urine in the test tube, rinse the pipette in distilled water and then add 1 drop of 20 percent potassium chromate. The mixture in the test tube now appears a bright yellow colour. Rinse the pipette again, add silver nitrate 2.9 percent solution;make sure is one drop at a time. Shake the test tube thoroughly after each drop. The end point is a sudden and definite colour change to red. The number of drops of sodium nitrate solution required to obtain the red colour is equivalent to the number of grams of chloride per litre of urine.
This test is used as a guide to the assessment of some errors of protein metabolism in infants which may lead to mental deficiency.
The phenistix is dipped into the specimen of urine or simply moistened by pressing against a wet napkin diaper. Leave the stick in contact with the urine for thirty seconds then compare the colour at the test end of the stick against the colour scale provided. If the result is positive, a grey to deep grey/green colour appears after about thirty seconds.