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Jaundice or icterus describes the yellow staining of the tissues due to an
excess of bilirubin - unconjugated or conjugated. Normal serum bilirubin
is 3 to 17 micromol/l. Jaundice becomes clinically detectable at levels above
40 micromol/l. Good natural light is required to detect slight clinical jaundice.
Tissues which concentrate bilirubin best are those with a high content of elastic
tissue, i.e. skin, ocular sclera, and blood vessels. Raised bilirubin can
be the result of raised excretion or raised production: - raised production
can be the result of obstructive liver disease - however other liver enzymes (alkaline
phosphatase and gamma-GT) are usually increased
- in mechanical obstructive
liver disease more than 50% of the bilirubin is conjugated bilirubin (1)
Isolated
raised levels of bilirubin may be the result of a defect in conjugation of bilirubin
e.g. in Gilbert's disease. In Gilbert's disease there is an increase in levels
of unconjugated bilirubin. Other causes to consider if there is an isolated raised
unconjugated bilirubin level include haemolysis. If haemolysis is suspected then
this can be investigated via the reticulocyte count, blood film, haptoglobin measurement
and lactate dehydrogenase levels (1). Reference: - Doctor magazine
(January 27th 2007), 45.
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