Urobilinogen refers to a colorless matter that develops due to a decrease in bilirubin levels. Bilirubin is a yellow colored waste product that forms as a byproduct of the process of red blood cells degradation.
The liver is an important organ that carried out varied vital functions, including regulation of blood sugar levels in the body and manufacture of a digestive fluid known as bile. Bile fluid helps in digestion of foods eaten by a person.Decomposition and degradation of red blood cells also occurs in the liver. Thus, the liver is instrumental in bilirubin elimination from the body. Bilirubin gets removed from the body via feces and urine.
Most of urobilinogen that forms from bilirubin is also removed from the body. A minor percentage of urobilinogen is reabsorbed into the body and put back for circulation in the system. It gets eliminated at a later time in the form of urobilinogen in urine. This process is referred to as ‘enterohepatic urobilinogen cycle.’
Causes of urobilinogen in urine
Urobilinogen in urine, or its absence in urine, may occur due to the below listed causes:
- Increased levels of bilirubin may occur due to a process called hemolysis. This process can trigger the formation of increased amounts of urobilinogen growth in the intestines. Occurrence of different diseases in the liver, including conditions like hepatitis, cirrhosis, etc., may result in interruption of the ‘intrahepatic urobilinogen cycle.’ This can then result in excess urobilinogen levels in the body, which then gets converted into a yellowish matter known as urobilin. This substance eventually gets eliminated with urine, thereby causing urine to attain a yellowish hue.
- Reduced amounts of bilirubin production may occur due to certain obstructions in the varied ducts of the biliary system, thereby causing a reduction in the levels of urobilinogen. Subsequently, the amount of urobilinogen that is available for reabsorption by the body is also reduced. This can eventually lead to lower levels of urobilin removal in urine.
- Increased levels of urobilinogen can occur due to varied conditions such as liver cirrhosis, hemolytic anemia, excessive degradation of RBCs, restricted liver function, hepatic infection, and poisoning. Overuse or increased workload on the liver as well as elevated creation and re-absorption of urobilinogen by the body can also result in urobilinogen in urine.
- Increased levels of bilirubin present and circulating in the body tend to be eliminated from the body by the kidneys. This process along with anomalies that occur due to obstructions in the biliary system can trigger the removal of pale feces and yellowish urine with urobilinogen.
- Different kinds of antibiotics can destroy and kill the naturally occurring bacterial in the gut. Varied medications used to treat jaundice also have an adverse effect on gut function. These treatments prevent the easy passage of bilirubin across the bowels, thereby causing a reduction or nil occurrence of urobilinogen in the intestines. Eventually, the levels of urobilinogen removed via urine is also nil or significantly diminished.
- Low levels of urobilinogen in urine can also occur due to presence of disorders like congenital enzymatic jaundice. It can also be due to excessive acidic nature of urine, which in turn occurs due to the action of medicines like ascorbic acid or ammonium chloride.
- Oxidation of urobilinogen present in the bowels can trigger the formation of brown-colored stercobilin. This can change the color of stool and urine to the distinct yellowish hue.
Urobilinogen detection via urine tests
Urobilinogen in urine along with liver anomalies, varied types of jaundice, and bilirubin levels can be checked via a urinalysis or other urine tests.
- Urobilinogen urine test is carried out with paper strips containing stable diazonium salt. Contact with any urobilinogen content in urine causes the strip to produce a reddish azo compound.Checking the color of urine can also help detect the presence of urobilinogen in urine.
- The different combinations of varied colors in the paper test strips are evaluated to verify the urobilinogen concentration levels in urine. A lab technician will be better equipped to assess the test results.
- The normal rate of urobilinogen removal via urine is fixed at 1 mg urobilinogen/dL of urine. Urobilinogen concentration in urine is usually low at 2 to 1.0 mg/dL or at below 17 micromol/L.
- The absence of urobilinogen in urine, or when it is present in levels that is higher or lower than normal, then it is regarded as being pathological. It may however be noted that such paper test strips usually do not detect the absence of urobilinogen in a sample of urine.
Some points to remember when evaluating a urobilinogen urine test are listed below:
- Excessive formaldehyde concentration in the urine specimen may produce false or nil results.
- Long term exposure of the sample of urine to light can produce false negative or wrong results.
- False positive or higher than normal readings may be seen due to presence of therapeutic or diagnostic dyes in the urine sample.
- Excessive amounts of bilirubin can cause the urine to be increasingly yellow.
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