Metabolism
on-line - the virtual tutorial room
copyright © 2008 - 2015 David A Bender
Hyperammonaemic coma due to liver failure
Mr ABV has been jaundiced for several days, and has come to see his GP
What is the cause of the yellow pigmentation of the skin (and especially the whites of the eyes) in jaundice?
Jaundice
is due to accumulation of bilirubin the blood plasma, giving it and his skin
a yellow colour.
Jaundice can develop for two reasons:
when bilirubin arising from the catabolism of haem in old red blood cells is not conjugated in the liver
when the bile duct is obstructed (e.g. with gall stones) so that bilirubin cannot be excreted in the bile
The GP suspects that Mr ABV's problem is viral hepatitis, but also thinks that it may be due to alcoholic liver damage, because she can smell alcohol on his breath, and on abdominal examination his liver is palpable and firm. She takes blood samples for both standard liver function tests (measurement of liver enzymes in the blood plasma) and also immunology to test for viral hepatitis.
On questioning, Mr ABV says he only drinks a glass or two of whisky each evening, and the occasional glass of wine.
The immunology results come back negative. The liver function test results are shown in the table below.
| enzyme | Mr ABV | reference range |
| aspartate transaminase | 2500 units /L | < 40 units /L |
| alanine transaminase | 1000 units /L | < 50 units /L |
| gamma-glutamyl transpeptidase | 1200 units /L | < 60 units /L |
| alkaline phosphatase | 2500 units /L | < 120 units /L |
Why are the activities of these enzymes in plasma elevated in liver disease?
They have been released from dead and dying liver cells. They indicate the extent of liver damage, but have no function in the bloodstream.