Bile Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Bile and links to relevant pages within the course.
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| Bilirubin Characterization Bilirubin, a product of hemoglobin breakdown, is characterized by its yellow pigment. The presence of bilirubin in urine is always abnormal. It is important to note that unconjugated bilirubin cannot be excreted by the kidneys because it is bound to albumin and is not soluble in water. In the liver, bilirubin combines with glucuronic acid through the action of a glucuronyl transferase to form water soluble bilirubin diglucuronide. Under normal circumstances, conjugated bilirubin passes from the bile duct and then to the intestinal tract. Intestinal bacteria reduce conjugated bilirubin to urobilinogen. Approximately half of the urobilinogen is excreted in the feces; most of the other half is recirculated through the liver. A small amount of urobilinogen bypasses the liver and is excreted in the urine. | View Page |
| Test for Bilirubin The test for bilirubin on the urine reagent strip is based on the formation of an azobilirubin compound resulting from a reaction of bilirubin in an acid medium with diazotized 2, 4 dichloroaniline. The color of this compound ranges through various shades of tan. Some sources describe the colors produced as shades of tan-to-pink-to-violet. Since other pigments in the urine may influence the test results, this test strip is more difficult to interpret than the others. Colors which are unlike either the positive or negative color blocks on the color chart may be due to the presence of bilirubin -derived bile pigments. Any urine which demonstrates an atypical color on the bilirubin test strip should be tested further. Even a slight change in color should be considered significant since bilirubin is never present in normal urine. | View Page |
| Confirmatory Testing Confirmatory testing using an alternative method such as Ictotest reagent tablets can be performed when positive results are seen on the dipstick strip, when a red color forms on the strip, or when atypical color changes occur that are the result of bilirubin-derived bile pigments in the urine masking the bilirubin reaction. | View Page |
| Clinical Significance Liver damage or an obstructed bile duct allows conjugated bilirubin to enter the circulation and ultimately to appear in the urine. Patients with clinical jaundice due to hepatitis or cirrhosis will have bilirubinuria. If the jaundice is due to red cell destruction, there is an increase in unconjugated bilirubin which the kidneys cannot excrete. | View Page |
| When a patient has a bile duct obstruction, the bilirubin test portion of the reagent strip is: | View Page |
| Urobilinogen Urobilinogen is a byproduct of hemoglobin breakdown. It is produced in the intestinal tract as a result of the action of bacteria on bilirubin. Almost half of the urobilinogen produced recirculates through the liver and then returns to the intestines through the bile duct. Urobilinogen is then excreted in the feces where it is converted to urobilin. As the urobilinogen circulates in the blood to the liver, a portion of it is diverted to the kidneys and appears as urinary urobilinogen. Up to 1 mg/dL or Ehrlich unit of urobilinogen is present in normal urine. A result of 2.0 mg/dL represents the transition from normal to abnormal and the patient should be evaluated further. It is important to note that the reagent strip cannot determine the absence of urobilinogen. | View Page |
| Elevation in conjugated bilirubin is most likely to be found in which of the following conditions: | View Page |
| Match the differential/ selective enteric medium with its characteristic indicator, fermentable, and bacteriostatic. | View Page |
| Group A beta-hemolytic streptococci are best characterized by which of the following: | View Page |
| Which of the following streptococcus exhibits a positive bile solubility test: | View Page |
| MacConkey agar contains all of the following except : | View Page |
| Urine Bilirubin Bilirubin is formed as a result of the breakdown of hemoglobin from erythrocytes in the reticuloendothelial system. It becomes bound to albumin and transported through the blood to the liver. This free or unconjugated bilirubin is insoluble in water and cannot be filtered through the glomerulus of the kidney. In the liver, bilirubin becomes conjugated with glucuronic acid to form bilirubin diglucuronide. This conjugated bilirubin, which is also called direct bilirubin, is water soluble and is excreted by the liver through the bile duct and into the duodenum. | View Page |
| Urine Bilirubin Normally, small amounts of conjugated bilirubin, regurgitate back from the bile duct and enter the blood stream, so small amounts of conjugated bilirubin can be found in the plasma. Since conjugated bilirubin is not bound to protein, it is easily filtered through the glomerulus and excreted in the urine whenever the plasma level is increased. Normally, no detectable amount of bilirubin (sometimes referred to as “bile”) is found in the urine. | View Page |
| The name of the rapid test as illustrated in this photograph, often used to differentiate S. pneumoniae from viridans streptococci, in which a drop of 10% deoxycholate was placed on an area of growth, is: | View Page |
| The colonies shown in the blood agar (upper) and MacConkey agar (lower) biplate are a 24 hour growth from an aerobic blood culture bottle that became positive at 12 hours after inoculation. The appearance of the colonies on MacConkey agar rules out the following two bacterial species: | View Page |
| Enterococcus ID Illustrated in this composite photograph is the gram stain of Enterococcus species (upper), illustrating gram positive cocci arranged in pairs and short chains.The viridans streptococci generally form gram positive cocci in long chains; the gram-positive cells of S. pneumoniae, on the other hand, may appear similar in gram stain.In the lower right is shown a 6.5% NaCl tube. The turbidity indicates growth, a unique characteristic for Enterococcus species.In the lower left frame is a picture of a bile esculin hydrolysis slant, showing a positive reaction (black pigment) characteristic of Enterococcus species. The streptococci are uniformly negative.Some strains of Leuconostoc species and Pediococcus species can grow in 6.5% NaCl and are bile-esculin positive; however, they should be ruled out because of the negative PYR reaction. | View Page |