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The presence of bile salts in urine can be detected by performing two popular tests, namely, Smith’s Test and Pettenkofer’s Test. In the smith’s test the presence of a green ring between layers will ensure the presence of bile salts in urine. However, in Pettenkofer’s Test, the presence of a red ring between layers will determine the presence of bile test in urine. Bile salts are one of the significant components of bile juice. They’re synthesised from cholesterol present in the liver. The deficiency of bile salts in the body can lead to diarrhoea, stomach cramps, bad-smelling gas, weight loss etc.
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Key Terms: Bile Salt, Bile Juice, Smith’s Reagent Test, Pettenkofer’s Test, Urine, Digestion, Fats, Fatty Acids, Absorption
What is Bile Salt?
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Bile salt is one of the components of bile juice which is a yellow-green fluid produced by the liver and stored in gallbladder. Bile juice is composed of bile pigments (bilirubin and bili-verdin), bile salts, cholesterol and phospholipids but no enzyme. They are composed of four different kinds of salts of free bile acids, namely, cholic acid, deoxycholic acid, chenodeoxycholic acid, and lithocholic acids.
Bile salts are produced by the liver and synthesised from cholesterol. It is an alkaline substance, so, when an alkaline substance meets an acid, it causes a neutralisation reaction. Bile salts play a significant role in breakdown of fats into fatty acids.
Bile Salt Structure
Role of Bile Salts
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Bile Salts help in the digestion of fats in ingested food. The primary functions of bile salt include breakdown of fats, digestion, absorption of important vitamins and elimination of toxins. Fats are insoluble in water and are present as large globules. They must be broken down for their digestion. The bile salts break these big globules into small particles called micelles. They’re then excreted from bile into the small intestine. From the small intestine, about 90% of bile salts are reabsorbed into the bloodstream. The liver takes out these bile salts from the blood and resecretes back into the bile juice. This cycle takes place about 10 to 12 times a day. Adult humans produce around 400 to 800 ml of bile daily.
Tests to Detect Bile Salts in Urine
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Two major tests for detecting bile salt in urine are as follows:
- Smith’s Reagent Test
- Pettenkofer’s Reagent Test
Smith’s Reagent Test
Aim: To test bile salt in urine using Smith reagent test
Material Required:
- Urine sample
- Test tube
- Dropper
- Measuring cylinder
- Smith’s reagent
Procedure:
- Take a clean and dried test tube.
- Measure 1 mL of Smith’s reagent in the test tube with the help of the measuring cylinder.
- Take a few drops of collected urine samples into the dropper.
- Hold the test tube in an inclined position and slowly add dropwise urine into the test tube.
- Observe the changes occured and keep a note of the same.
Result:
The formation of green rings at the intersection of both the layers (urine and smith reagent) will indicate the presence of bile salt in urine.
Pettenkofer’s Reagent Test
Aim: To test bile salt in urine using Pettenkofer’s Test
Material Required:
- Test tube
- Spatula
- Dropper
- Sucrose
- Urine sample
- Measuring cylinder
- Concentrated H2SO4
Procedure:
- Take a clean and dried test tube.
- Measure 2 mL of urine sample in measuring cylinder and add it into the test tube.
- Add some sucrose with the help of a spatula into the test tube containing urine.
- Now measure 2 mL of concentrated H2SO4 in the measuring cylinder.
- Hold the test tube in an inclined position and slowly add the concentrated H2SO4 into the test tube.
- Observe the changes occured and keep a note of the same.
Result:
The formation of red rings at the intersection of both the layers (urine and smith reagent) will indicate the presence of bile salt in urine.
Things to Remember
- Bile salts are the components of bile juice which include cholate and chenodeoxycholate. They’re synthesised from cholesterol in the liver.
- The bile salt levels get elevated in patients with obstructive jaundice or cholestasis and can cause bile acid malabsorption (BAM). They include watery stool, urgency and faecal incontinence etc.
- The deficiency of bile salt can lead to Crohn’s disease, diarrhoea, stomach cramps, bad-smelling gas, weight loss etc.
- The increase in bile salt in the body will increase the bile acids in blood. These bile acids then enter the colon and can cause various diseases.
- The presence or absence of bile salt in urine can be tested by two main tests, namely, Smith’s Test and Pettenkofer’s test. In both tests, we collect urine samples in a test tube and add the respective reagents. In the smith test, the appearance of the green ring ensures the presence of bile salt whereas in Pettenkofer’s Test, the appearance of the red ring determines the presence of bile salt.
Sample Questions
Ques. Are bile salt and bile juice the same? Where are they stored? (2 marks)
Ans. No, bile salts are not a bile juice, rather it is a component of bile juice. These terms are used interchangeably most of the time, but technically they are different. Bile salts are formed when bile acid is combined with amino acids like glycine or taurine. So, bile acid turns into bile salts when conjugated with these amino acids. Bile juice consists of bile pigments (bilirubin and bili-verdin), bile salts, cholesterol, and phospholipids but no enzyme. They are temporarily stored in the gallbladder. When it is required, it gets released from the gallbladder for the digestion of fat in the small intestine.
Ques. Bile salt helps in elimination of bilirubin. Elaborate. (3 marks)
Ans. Yes, Bile salt helps in elimination of bilirubin. Bilirubin is a yellow pigment which is formed during the normal breakdown of red blood cells. It goes through the liver and is eventually excreted out of the body. The high bilirubin levels may indicate different types of liver or bile duct problems. Presence of too much bilirubin in the skin and mucous membranes can lead to jaundice, a condition in which the skin and whites of eyes become yellow, urine becomes darker, and the colour of stool becomes lighter.
Ques. What if bile salts decrease in the body? (2 marks)
Ans. There should be an optimum level of bile salts in the body. If due to some reason, the body gets deficient, then it can cause Crohn’s disease, diarrhoea, stomach cramps, bad-smelling gas, weight loss etc. In severe cases, if remains untreated for a long time may increase risk of forming kidney stones and gallstones. They’re also responsible for Crohn’s disease.
Ques. What are the major functions of bile salts? (3 marks)
Ans. The major functions of bile salts are as follows:
- Help in digestion of fats.
- They fight against infections
- Remove cholesterol and other toxic compounds
- Dissolve gallstones
- Promote liver and gallbladder function
- Digestion and absorption of nutrients
- Control blood sugar
- Eliminate bilirubin
- Trigger release of glutathione etc.
Ques. Do bile salts help in gallbladder and liver function? (2 marks)
Ans. Yes, bile salts help in gallbladder and liver function. They help in gallbladder function by reducing inflammation of the bile ducts and thus normalise the flow of blood. They help in liver function by improving the symptoms of disease affecting the liver, by removing toxic substances and pathogens from the body.
Ques. How bile salts help in removing cholesterol? (2 marks)
Ans. Cholesterol is a fatty substance and too much cholesterol can accumulate plaque in your arteries which can lead to heart disease and stroke. Cholesterol is secreted into bile. Cholesterol is insoluble in water-based solutions, but when it combines with bile, it gets solubilized by bile salts present in bile juice. Now this cholesterol can be transported and removed from the body through digestion. About 500 milligrams of cholesterol is eliminated in our bile every day.
Ques. Mistakenly Renu has used concentrated sulphuric acid instead of smith reagent and added some sucrose in urine samples. She saw a red ring instead of green. What can be the possible reason? (2 marks)
Ans. Renu has used Pettenkofer’s test for testing bile salt in urine. In this test, a urine sample is added into the test tube. Then, some sucrose was added along with concentrated sulphuric acid through the sides of the test tube. The appearance of a red ring at the intersection of both the layers (urine and smith reagent) indicates the presence of bile salt in urine.
Ques. Are bile salts amphipathic? How do they help in cholesterol regulation? (2 marks)
Ans. Yes, bile salts are amphipathic. They mean that they have both a water- and fat-soluble region. They help in emulsification of fat which causes the breakdown of large fat globules into minute fat droplets (micelles). Emulsification increases the surface area of fat which allows easy digestion by lipases, which cannot access the inside of lipid droplets. They solubilize the micelles which remain suspended in water.
Ques. How bile salts work as a defence mechanism of the body? (2 marks)
Ans. Bile acids or salts work as a defence mechanism by fighting against infectious agents and toxins. These agents are responsible for causing several diseases like sepsis, herpes and parvovirus etc. As per recent research, such a type of defence mechanism is called a “physico-chemical defence system,”. This mechanism is only effective if the body has an optimum level of bile salts in the body.
Ques. Which bile salt supplements can be taken to avoid deficiency of bile salt in the body? (2 marks)
Ans. To get rid of deficiency of bile salt, a person can stay well-hydrated. This is because about 85% of bile is made up of water. In addition to this, intake of beets and beets greens can also be increased in diet. This is because they are a house of bulk nutrients and help in the detoxification of the liver.
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