Chemical tests for urine
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Chemical Tests for Urine
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Heat and Acetic Acid Test
(Protein)
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A. Heat and Acetic Acid Test(Protein)
• Principle: based on precipitation by heat and coagulation by acids. (See chapter 4)
• Procedure:– Fill test tube with urine (2/3 full)
centrifuge.– Heat the upper 2cm of the urine and
observe the cloudiness. (Due to phosphates not albumin).
– Add 2 to 3 drops of 10% acetic acid. Cloudiness due to phosphates will disappear.
– Repeat the heating. Persistent cloudiness indicates albumin. (Proteinuria)
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• If cloudiness developed at 40-60° C and disappears upon boiling but reappears on cooling, the protein present is called Bence-Jones protein. This protein is encountered in:
• Hyperglobulinemia -A condition characterized by abnormally large amounts of globulins in the blood. And in
• Multiple myeloma -also known as plasma cell myeloma, is the second-most common cancer of the blood.
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Test for Sugar(Benedict’s Test)
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• Principle: Reduction of Cupric (blue) to Cuprous (brick red) by the reducing sugars.*
• Procedure:– Place 5cc. Of Benedict’s
reagent (Copper sulfate, sodium carbonate, and sodium citrate) in a test tube.
– Add 8 to 10 drops of urine, mix by shaking and boil vigorously in water bath for 5mins.
• Positive result: Brick red ppt.
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Test For Bilirubin
(Foam Test)
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• Principle: Bilirubin if present colors the foam yellow to green.
• Procedure:– Place 5ml urine in a test tube. Place cover.– Shake the urine vigorously for 3 mins.– If Bilirubin is present, the foam produced will
have a yellow to light green color.
In patients with proteinuria, bilirubin bound to albumin can also appear in urine.*
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Test For Blood(Benzidine Test)
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• Principle: The peroxide activity of the blood decomposes hydrogen peroxide and the liberated oxygen oxidizes the benzidine.
• Procedure:– Place 1cc of Benzidine solution in a test tube.– Add 0.5cc of urine which was previously
filtered.
– Add 0.3cc of H2O2 to the mixture.
–Mix and observe for a change in color.• Positive result: Green or blue color. (Hematuria)
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Test For Chlorides(Fantus Test)
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• Principle: AgNO3 reacts with the chloride in urine to precipitate AgCl. Any excess AgNO3 reacts with Potassium Chromate to form reddish ppt. Of Ag2CrO4 . The appearance of which indicates end point.
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• Procedure:– Place 10 drops of urine to a test tube and
one drop k2CrO4 solution as indicator.
– Add drop by drop 2.9% AgNO3 solution until a permanent red brown color (end point) is developed.
– The number of drops consumed represent amount of chloride present. Normally 6 to12 drops.
May indicate Hyperchloremia if it exceed 12.
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Feces• Are food materials which escaped the digestive process and are passed through the large intestine to the outside.
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Composition of Feces• Indigestible and
unabsorbed food residue. Eg. Vegetable fibers, muscle fibers, iron compounds, calcium salts.
• Secretions from gastro intestinal tract. Eg. Lipids
• Excreted materials like mucous and bile
pigments.
• Bacteria like Esheria Coli.
• Ephithelial cells and other pathological
constituents like blood and pus.
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Physical Characteristics
• Color– Adult fecal material is normally brown in
color.
– Thus this attributed to hydrobilirubin (reduced) and storcobilin (from bile pigments).
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– But, the colors are dependent upon the nature of the diet, and also upon certain drugs.
– Examples:• Yellow- milk diet• Dark gray- Chocolate• Dark green- Spinach; calomel due to
biliverdin*.• Dark brown or black- Bismuth and Iron
compounds• Red- Neoprontosil• Clay color- connected with X-ray
examinations
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• Abnormal Colors (pathological)– Golden yellow- due to unchanged
bilirubin– Green- Diarrhea of children with faulty
carbohydrate metabolism– Clay color- Deficiency in bile; observed
in conditions such as jaundice when there is obstruction of the bile duct so that bile cannot reach the intestine.
– Red streaks of blood- can be due to bleeding hemorrhoids. Can also be carcinoma* and other lesions of the rectum or anus.
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• Odor– The offensive odor is due to indole and
skatole*– Other gases contributing to the odor
includes methane and hydrogen sulfide.• Offensive odor is accentuated by a diet
consisting largely of meat.• Very foul odor may suggest ulceration in the
intestines or rectum. Also observed in cancer, syphilis and gangrenous dysentery.*
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• Reaction– Normal reaction is slightly acidic or
slightly alkaline– It is acidic when there is predominance
of carbohydrate food in the diet; alkaline when there excess of protein material.
– This reaction can be tested with litmus paper or alizarin indicator
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• Form and consistency– These vary from a thin pastry discharge
to a firmly formed stools.– However, these again may vary
depending upon the condition of the individual and his diet.
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– Variations in the form and consistency which are pathological includes:• Soft or watery stools- indicates diarrhea or
administration of cathartics• Very hard- indicates constipation• Hard Rounded Scybalous- Atony of the colon
as in infection of the appendix.• Flattened ribbon-like stools- obstruction of
the colon. (may indicate colon cancer).
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• Amount– About 80 to 200 grams per day are
eliminated– Usually it is eliminated together with
variable amounts of gases such as:• Hydrogen- when milk predominates the diet• Methane- vegetable diet• Nitrogen- meat or mixed diet
• In all cases CO2 and H2S are present
– The bulk increases if large amounts of vegetable is present in the diet.
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Chemical Tests