This has now been replaced in most centres by ultrasound. Oral iopanoic acid is absorbed from the gut, conjugated in the liver, secreted in bile and concentrated in the gallbladder, which opacifies homogeneously. A fatty meal is given to make the gall bladder contract. The dye is excreted by the liver via the same mechanism as bilirubin, so that non-visualization will occur in the jaundiced patient and in the patient with liver disease.
This has been replaced by ultrasound and endoscopic retrograde cholangiopancreatography. Radionuclide imaging – scintiscanning
TECHNETIUM-99M (99mTc) COLLOID SCAN. This colloid, when injected intravenously, is taken up by the reticuloendothelial cells of the liver and spleen. It can show space-occupying lesions and a generalized decrease in uptake is found in parenchymal disease of the liver. Since the introduction of ultrasound this technique is used less frequently, Currently its main uses are in:
ADVANCED CIRRHOSIS in which there is poor uptake in the liver and most of the colloid is taken up in the spleen and bone marrow
ALC0 H0 LIC HEPATITI S in which there is virtually no uptake in the liver owing to Kupffer cell damage by alcohol 99mTc-HIDA SCAN. 99mTc-HIDA (an imino-diacetic acid derivative) is taken up by the hepatocytes and excreted rapidly into the biliary system. Its main uses are in the diagnosis of:
• Acute cholecystitis
• Hepatitis due to biliary atresia in the neonatal period Endoscopy
This is used for the diagnosis and treatment of varices and for the detection of portal hypertensive gastropathy. Endoscopic retrograde cholangiopancreatography (ERCP)
This technique is used to outline the biliary and pancreatic ducts. It involves the passage of an endoscope into the second part of the duodenum and cannulation of the ampulla. Contrast is injected into both systems and the patient is screened radiologically. Contrast medium with a low iodine content of 1.5 mg ml ” is used for the common bile duct so that gallstones are not obscured; a higher iodine content of 2.8 mg mr ‘ is used for the pancreatic duct. In addition, other diagnostic and therapeutic procedures can be carried out:
REMOVAL OF COMMON BILE DUCT STONES after a diathermy cut to the sphincter has been performed to facilitate their withdrawal
DRAINING THE BILIARY SYSTEM by passing a tube (stent) through an obstruction
Complications include cholangitis, and broad-spectrum prophylactic antibiotics, e.g. i.v. cefotaxime 1 g 8-hourly, should be given to all patients with suspected biliary obstruction. A raised serum amylase is often seen and pancreatitis can occur. The presence of a pancreatic pseudocyst is a relative contraindication.
Percutaneous transhepatic cholangiography (PTC) Under a local anaesthetic a fine, flexible needle is passed into the liver. Contrast is injected slowly until a biliary radicle is identified and then further contrast is injected to outline the whole of the biliary tree. The main use of PTC is in jaundiced patients who have been shown to have dilated intrahepatic ducts demonstrated on ultrasound. The choice of ERCP or PTC often depends on local expertise. Sometimes the two techniques are performed together, PTC showing the biliary anatomy leading to an obstruction, while ERCP shows the more distal anatomy. If an obstruction in the bile ducts is seen, a bypass stent can sometimes be inserted either draining externally or, for long-term use, internally. Contraindications are as for liver biopsy (see below). The main complications are bleeding and cholangitis with septicaemia, and prophylactic antibiotics should be given as for ERCP.
This can be performed by selective catheterization of the coeliac axis and hepatic artery, and is useful for detecting the abnormal vasculature of hepatic tumours. The portal vein can be demonstrated with increased definition using subtraction techniques, and splenoportography (by direct splenic puncture) is now rarely performed. In digital vascular imaging (DVI), contrast given intravenously or intra-arterially can be detected in the portal system using computerized subtraction analysis. Attempted visualization of the hepatic veins by venography is particularly important in the diagnosis of the Budd-Chiari syndrome.
Hepatic venous cannulation also allows an indirect measurement of portal pressure to be made, although this has seldom been shown to be of any diagnostic or therapeutic value.
Histological examination of the liver is valuable in the differential diagnosis of diffuse or localized parenchymal disease. Liver biopsy can be performed either on a daycase or overnight-stay basis. The indications and contraindications are shown in Table 5.2. The mortality rate is less than 0.02% when performed by experienced operators. Liver biopsy is now often performed under ultrasound or CT control particularly when specific lesions need to be biopsied.
Laparoscopy with guided liver biopsy is performed through a small incision in the abdominal wall under local anaesthesia. General anaesthesia is preferred in some centres.
A transjugular approach is used when liver histology is essential for management but coagulation studies prevent the percutaneous approach.
Most complications occur within 24 hours usually in the first 2 hours. They are usually minor and include abdorninal or shoulder pain which settles with analgesics. Minor intraperitoneal bleeding is common but this settles spontaneously. Rare complications include major intraperitoneal bleeding, pleurisy and perihepatitis, biliary peritonitis, haemobilia and transient septicaemia. Haemobilia produces biliary colic, jaundice and melaena within 3 days of the biopsy.