Chemical Tests for Urine

Heat and Acetic Acid Test

(Protein)

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)

• 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.

Test for Sugar(Benedict’s Test)

• 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.

Test For Bilirubin

(Foam Test)

• 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.*

Test For Blood(Benzidine Test)

• 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)

Test For Chlorides(Fantus Test)

• 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.

• 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.

Feces• Are food materials which escaped the digestive process and are passed through the large intestine to the outside.

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.

Physical Characteristics

• Color– Adult fecal material is normally brown in

color.

– Thus this attributed to hydrobilirubin (reduced) and storcobilin (from bile pigments).

– 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

• 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.

• 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.*

• 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

• 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.

– 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).

• 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.

Chemical Tests