4.7 BILIRUBIN AND UROBILINOGEN Flashcards
Identify the form of bilirubin that appears in the urine when liver disease disrupts the normal bilirubin degradation cycle.
Conjugated bilirubin
Identify the key factor that causes bilirubin to appear in the urine.
Disruption of the normal bilirubin degradation cycle due to bile duct obstruction or liver damage.
Identify the types of jaundice associated with bilirubinuria.
Posthepatic jaundice (bile duct obstruction) and hepatic jaundice (liver damage).
Identify the test method commonly used to detect bilirubin in urine
The diazo reaction with reagent strips.
Identify the chemical used in the diazo reaction for detecting bilirubin in urine.
2,4-dichloroaniline diazonium salt or 2,6-dichlorobenzene-diazonium-tetrafluoroborate.
Identify the common interferences that can cause a false-positive result in bilirubin testing
Urine pigments (e.g., phenazopyridine compounds), indican, and metabolites of Lodine
Identify the factor that commonly causes a false-negative result in bilirubin testing
Exposure of the specimen to light, which causes bilirubin to photo-oxidize into biliverdin
Identify the confirmatory test for bilirubin in urine.
The Ictotest
Identify the sensitivity of the Ictotest for bilirubin detection.
0.05 to 0.1 mg/dL of bilirubin.
Identify the key byproducts of bilirubin metabolism in the intestine
Urobilinogen and stercobilinogen
Identify the normal concentration range for urobilinogen in urine.
Less than 1 mg/dL (1 Ehrlich unit).
Identify the clinical conditions that cause an increase in urinary urobilinogen.
Liver disease and hemolytic disorders
Identify the reagent used in Multistix to detect urobilinogen
p-dimethylaminobenzaldehyde (Ehrlich reagent).
Identify the reagent used in Chemstrip to detect urobilinogen.
4-methoxybenzene-diazonium-tetrafluoroborate
Identify the potential interference that could cause false-positive results in the Multistix urobilinogen test.
Ehrlich-reactive compounds such as porphobilinogen, indican, and certain medications (e.g., sulfonamides, methyldopa)
Identify the condition in which the absence of urobilinogen in urine and feces is diagnostically significant.
Biliary obstruction.
Identify the main pigment responsible for the brown color of feces
Stercobilin
Identify the compound that is produced when urobilinogen is oxidized in the intestine.
Urobilin
Identify the liver condition that results in the leakage of conjugated bilirubin into the bloodstream, causing bilirubinuria.
Hepatitis or cirrhosis
Identify the condition that can cause the absence of bilirubin in the urine despite the presence of jaundice.
Hemolytic disease, where unconjugated bilirubin is present in the serum but not excreted in the urine.
Identify the type of jaundice caused by gallstones or cancer obstructing the bile duct
Posthepatic (biliary) jaundice
Identify the substance formed when bilirubin undergoes conjugation in the liver.
Bilirubin diglucuronide (conjugated bilirubin
Identify the main reason bilirubin is not normally found in the urine under healthy conditions
Conjugated bilirubin is excreted into the bile and passed into the intestine, not the urine
Identify the organ responsible for converting bilirubin into urobilinogen in the intestine
Intestinal bacteria.
Identify the substance that results from the oxidation of urobilinogen in the feces
Stercobilin
Identify the substance formed when urobilinogen is oxidized in the urine
Urobilin
Identify the testing procedure that uses p-nitrobenzenediazonium-p-toluenesulfonate for bilirubin detection.
Ictotest procedure
Identify the color change that indicates a positive result for bilirubin in the Ictotest
A blue-to-purple color
Identify the clinical significance of increased urinary urobilinogen in a patient with liver disease
Impaired liver function leads to decreased processing of recirculated urobilinogen, causing excess urobilinogen to be filtered by the kidneys and appear in the urine.
Identify the clinical significance of absent urobilinogen in the urine and pale stools.
Biliary obstruction preventing the normal passage of bilirubin into the intestine.
Identify the substance that causes a false-negative result in urobilinogen testing when specimens are improperly preserved
Photo-oxidation of urobilinogen to urobilin
Identify the test used for detecting urobilinogen in urine that produces a pink color with a positive result.
The Multistix test using the Ehrlich reaction
Identify the reagent used in the Ehrlich reaction for urobilinogen detection on Multistix.
p-dimethylaminobenzaldehyde (Ehrlich reagent).
Identify the type of chemical reaction used by Chemstrip to detect urobilinogen in urine
Azo-coupling (diazo) reaction
Identify the condition where urobilinogen can be elevated due to hemolysis
Hemolytic disorders, where increased unconjugated bilirubin leads to more urobilinogen production
