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TABLE 19.10 Testing and classifying liver function 269,273

Blood test Normal value Description
Alanine aminotransferase ALT: <35 U/L ● ALT and AST are enzymes that indicate liver cell damage; they are produced within the liver
(ALT) and aspartate AST: <40 U/L cells (hepatocytes) and leak out into the general circulation when the liver cells are damaged.
aminotransferase (AST) ● ALT is a more specific indication of liver inflammation.
● In acute liver injury, ALT and AST may be elevated to the high 100s, even 1000s, U/L.
● In chronic liver damage such as hepatitis or cirrhosis, there may be mild to moderate
elevation (100–300 U/L).
● ALT and AST are commonly used to measure the course of chronic hepatitis and the
response to treatments.
Alkaline phosphatase ALP: 25– ● These are enzymes that indicate obstruction to the biliary system.
(ALP) and gamma- 100 U/L ● They are produced in the liver, or within the larger bile channels outside the liver.
glutamyl-transpeptidase GGT: Males ● The GGT is used as the supplementary test to be sure that a rise in ALP is indeed coming
(GGT) <50 U/L from the liver or biliary tree.
Females
<30 U/L ● A rise in GGT but normal ALP may indicate liver enzyme changes induced by alcohol or
medications, causing no injury to the liver.
● ALP and GGT are commonly used to measure bile flow obstructions due to disorders such as
gallstones, a tumour blocking the common bile duct, biliary tree damage, alcoholic liver
disease or drug-induced hepatitis.
Bilirubin < 20 µmol/L Results from the breakdown of red blood cells. Thus bilirubin is protein-bound and circulates in
the blood in an unconjugated form. The liver processes bilirubin to a water-soluble
conjugated form that is excreted in the urine and faeces.
● Liver injury or cholestasis results in an elevated bilirubin level.
● Raised unconjugated bilirubin without an accompanying rise in conjugated bilirubin is
consistent with red blood cell destruction (haemolysis).
● Raised bilirubin levels result in jaundice.
● In cases of chronic liver disease, bilirubin levels usually remain normal until significant
damage occurs and cirrhosis develops.
● In cases of ALF, bilirubin levels will rise rapidly and result in marked jaundice; the degree of
rise is indicative of the severity of illness.
Albumin 32–45 g/L ● Albumin is a major protein formed by the liver; it provides a gauge of liver synthetic function
(i.e. albumin levels are lowered in liver disease).
Clinical assessment: Model Developed to predict mortality risk and assess disease severity in patients with cirrhosis. The
for end-stage liver score is calculated from a mathematical model using values of bilirubin, INR, creatinine, and
disease (MELD) score aetiology (whether cholestatic or alcoholic).

oedema and raised intracranial pressure due to ALF are Transplantation). 270,271 These tests have been summarised
managed primarily as patients with acute head injury in Table 19.10. 253,272
(see Chapter 17).
Treatment
COLLABORATIVE PRACTICE ALF or AoCLF therapy often involves the support and

The collaborative management of ALF focuses on provid- treatment of the consequences of liver failure, such as
ing interim support until either hepatic recovery occurs sepsis, encephalopathy, renal failure and coagulopathy
or liver transplantation is undertaken. (see Table 19.11). One specific support therapy that may
be used to prevent further liver cell injury is administra-
Assessment of Liver Function tion of N-acetylcysteine (NAC), a glutathione donor that
Patients presenting with ALF require a careful history to acts to replenish liver cellular stores of this scavenger of
establish the cause of liver injury. The well-known signs toxic oxygen free-radicals. Inflammation, the accumula-
of chronic liver disease (e.g. palmar erythema, spider tion of bile acids, and ischaemia/reperfusion results in
naevi and ascites) may not be present. Biochemical and the build-up of oxygen free-radicals, which can induce
237
haematological tests determine whether liver cell injury hepatic necrosis if not controlled.
is occurring, with liver synthesis and clearance functions Oesophageal balloon tamponade and
assessed by albumin level and prothrombin time, and
bilirubin level respectively. 269 These measures have been transjugular intrahepatic portosystemic
incorporated into a scoring system to determine stent/shunt
liver dysfunction and prognostic information for liver There are two types of balloon tamponade devices available
transplantation suitability (model for end-stage liver on the market: the Sengstaken-Blakemore tube (see Figure
disease [MELD], see later in this chapter under 19.1) and the Linton tube. The Sengstaken-Blakemore is a