Chapter 7 Liver, biliary tract and pancreatic disease
The liver
Structure of the liver and biliary system
The liver
The hepatic artery, a branch of the coeliac axis, supplies 25% of the hepatic blood flow. The hepatic artery autoregulates flow ensuring a constant total blood flow.
The portal vein drains most of the gastrointestinal tract and the spleen. It supplies 75% of hepatic blood flow. The normal portal pressure is 5–8 mmHg; flow increases after meals.
Functions of the liver
Formation of bile
Bile secretion and bile acid metabolism
The bile acids are excreted into bile and then pass via the common bile duct into the duodenum. The two primary bile acids – cholic acid and chenodeoxycholic acid (Fig. 7.4) – are conjugated with glycine or taurine, which increases their solubility. Intestinal bacteria convert these acids into secondary bile acids, deoxycholic and lithocholic acid. Figure 7.5 shows the enterohepatic circulation of bile acids.
Hormone and drug inactivation
The liver catabolizes hormones such as insulin, glucagon, oestrogens, growth hormone, glucocorticoids and parathyroid hormone. It is also the prime target organ for many hormones (e.g. insulin). It is the major site for the metabolism of drugs (see p. 348) and alcohol (see p. 225). Fat-soluble drugs are converted to water-soluble substances that facilitate their excretion in the bile or urine. Cholecalciferol is converted to 25-hydroxycholecalciferol.
Investigations
Investigative tests can be divided into:
Urine tests – for bilirubin and urobilinogen
Imaging techniques – to define gross anatomy
Blood tests
Useful blood tests for certain liver diseases are shown in Table 7.1.
Table 7.1 Useful blood and urine tests for certain liver diseases
Test | Disease |
---|---|
Anti-mitochondrial antibody | Primary biliary cirrhosis |
Anti-nuclear, smooth muscle (actin), liver/kidney microsomal antibody | Autoimmune hepatitis |
Raised serum immunoglobulins: |
|
IgG | Autoimmune hepatitis |
IgM | Primary biliary cirrhosis |
Viral markers | Hepatitis A, B, C, D, E and others |
α-Fetoprotein | Hepatocellular carcinoma |
Serum iron, transferrin saturation, serum ferritin | Hereditary haemochromatosis |
Serum and urinary copper, serum caeruloplasmin | Wilson’s disease |
α1-Antitrypsin | Cirrhosis (± emphysema) |
Anti-nuclear cytoplasmic antibodies | Primary sclerosing cholangitis |
Markers of liver fibrosis | Non-alcoholic fatty liver disease |
| Hepatitis C |
Genetic analyses | e.g. HFE gene (hereditary haemochromatosis) |
Liver biochemistry
Aspartate aminotransferase (AST) is primarily a mitochondrial enzyme (80%; 20% in cytoplasm) and is also present in heart, muscle, kidney and brain. High levels are seen in hepatic necrosis, myocardial infarction, muscle injury and congestive cardiac failure.
Alanine aminotransferase (ALT) is a cytosol enzyme, more specific to the liver so that a rise only occurs with liver disease.
Additional blood investigations
Haematological
Bleeding produces a hypochromic, microcytic picture.
Alcohol causes macrocytosis, sometimes with leucopenia and thrombocytopenia.
Hypersplenism results in pancytopenia.
Cholestasis can often produce abnormal-shaped cells, and also deficiency of vitamin K.
Haemolysis may accompany acute liver failure and jaundice.
Aplastic anaemia occurs in up to 2% of patients with acute viral hepatitis.
A raised serum ferritin with transferrin saturation (>60%) is seen in hereditary haemochromatosis.
Biochemical
a1-Antitrypsin. A deficiency of this enzyme can produce cirrhosis.
α-Fetoprotein. This is normally produced by the fetal liver. Its reappearance in increasing and high concentrations in adults indicates hepatocellular carcinoma. Increased concentrations in pregnancy in blood and amniotic fluid suggest fetal neural tube defects. Blood levels are also slightly raised with regenerative liver tissue in patients with hepatitis, chronic liver disease and also in teratomas.
Raised urinary copper, and low serum cooper and caeruloplasmin in Wilson’s disease (see p. 341).
Immunological tests
Anti-mitochondrial antibody (AMA) in serum is found in over 95% of patients with primary biliary cirrhosis (PBC) (p. 338). Several different AMA subtypes are described, depending on their antigen specificity, and are also found in autoimmune hepatitis and other autoimmune diseases. AMA is demonstrated by an immunofluorescent technique and is neither organ- nor species-specific. M2 subtype is specific for PBC.
Nucleic, smooth muscle (actin), liver/kidney microsomal antibodies can be found in serum, often in high titre, in patients with autoimmune hepatitis. These serum antibodies can also be found in other autoimmune conditions and other liver diseases.
Anti-nuclear cytoplasmic antibodies (ANCA) can be found in serum of patients with primary sclerosing cholangitis.
Imaging techniques
Ultrasound examination
the detection of gallstones (Fig. 7.6)
focal liver disease – lesions >1 cm
general parenchymal liver disease
assessing portal and hepatic vein patency
Other abdominal masses can be delineated and biopsies obtained under ultrasonic guidance.
Endoscopic retrograde cholangiopancreatography (ERCP)
Common bile duct stones can be removed after performing a diathermy cut of the sphincter to facilitate their withdrawal. Sphincterotomy has a morbidity rate of 3–5%: acute pancreatitis is the commonest, severe haemorrhage is rare. There is an overall mortality of 0.4%.
The biliary system can be drained by passing a tube (stent) through an obstruction, or placement of a nasobiliary drain.
Brachytherapy can be administered after placement at ERCP for therapy of cholangiocarcinoma.
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