Percutaneous transhepatic cholangiography

A 22-gauge flexible Chiba needle is advanced through the skin and well into the liver under local anaesthesia and antibiotic cover. Blood coagulation must be normal. Contrast medium is gently injected as the needle is slowly withdrawn. The procedure is watched on an image intensifier: when contrast medium enters a bile duct withdrawal is stopped. Contrast medium is then injected to fill the whole biliary tree (Fig. 12) 1235. In skilled hands this can always be achieved if the bile ducts are dilated, and is also possible in about two-thirds of patients in whom the ducts are normal in size. It may be necessary to puncture both the right and the left hepatic systems to outline all the ducts. Bile leakage into the peritoneum, cholangitis, and haemorrhage are the major complications, occuring in about 4 per cent of patients. For this reason it is still best to plan to relieve any obstruction, either surgically or by the percutaneous insertion of a drain or stent, during or fairly soon after the examination. The mortality rate associated with the procedure is about 0.5 per cent.

 

Endoscopic retrograde cholangiopancreatography

A full description of this technique is given in Section 27.2 166. The ability to outline the biliary tree and the pancreatic duct as well as to inspect the ampulla of Vater has completely revolutionized the management of many benign biliary problems. Not only has diagnosis been improved (Fig. 13) 1236 but therapeutic techniques have been developed which have improved patient care significantly. Endoscopic retrograde cholangiopancreatography (ERCP) requires technical skill and sophisticated imaging, and is not as widely available as the percutaneous approach. The endoscopic route is preferred initially since it does not transgress the peritoneum, but there are occasions when it is essential to outline the bile ducts from above as well as from below.

 

Computed tomography

Computed tomography (CT) is useful in the diagnosis of biliary tract disease although the evidence is usually indirect. It is easier to identify pathology in the liver, the pancreas, and the gallbladder than the bile duct itself, although the ducts are easily seen when they are dilated (Fig. 14) 1237. CT is probably superior to ultrasonography in identifying the level and the cause of biliary obstruction, but the latter is cheaper, simpler, and safer.

 

Malignant disease in or around the biliary tree can best be staged by CT; this may also be needed to allow a biopsy to be undertaken. It is not of great value in the management of the common inflammatory conditions, where ultrasound is of greater use. However ultrasound and CT should be regarded as complementary investigations and in difficult cases it is common to use both.

 

Other imaging techniques

A variety of other imaging techniques may be of value. Intravenous cholangiography, where the bile ducts are outlined directly following intravenous administration of contrast medium, has largely been superseded by ERCP and percutaneous transhepatic cholangiography, which provide better detail.

 

Isotopic scanning of the gallbladder may be useful in the diagnosis of acute cholecystitis. A technetium-labelled derivative of iminodiacetic acid (HIDA, PIPIDA) is administered intravenously and images are then recorded by a gamma-camera (Fig. 15) 1238. In acute cholecystitis the cystic duct is occluded and so the gallbladder will not opacify; opacification excludes acute cholecystitis. A HIDA scan is particularly useful in the diagnosis of acute acalculous cholecystitis. False positive results may occur in patients with alcoholic liver disease and in those maintained on total parenteral nutrition, in whom the gallbladder is atonic. The isotope may fail to enter the gallbladder despite a patent cystic duct.

 

Arteriography is essential before any major operation on the biliary system because of the wide variation in biliary arterial anatomy (Fig. 16) 1239. The liver, gallbladder, and pancreas can all be imaged by magnetic resonance (MRI), but the information currently provided is no better than that obtained from CT.

 

Liver function tests

Biochemical measures of liver function abound. In a surgical context interest has focused on bilirubin, alkaline phosphatase, which is excreted by liver cells, and transferase enzymes, which are predominantly located within liver cells. Changes in these three parameters have traditionally been used to differentiate between intra- and extrahepatic causes of jaundice. A rise in alkaline phosphatase signifies an extrahepatic obstruction while changes in enzyme levels indicate disease within the liver cells themselves. These changes are never totally reliable and they have been superseded by ultrasound and the demonstration of dilatation of the bile ducts. They are, however, useful indicators of disease severity, and their main use is to monitor the effects of treatment. Prothrombin time is also a useful measure of liver function, since it depends on the synthetic functions of the liver. Prolongation of the prothrombin time, which might lead to excessive haemorrhage, must be corrected by the administration of Vitamin K or fresh frozen plasma before embarking on any surgical procedure.

 

Biliary manometry

Biliary manometry is used to assess the function of the sphincter of Oddi. Pressure traces can be obtained either by placing a special perfusion catheter across the sphincter from below at ERCP or from above during surgical exploration of the common bile duct. The former is used to detect stenosis and dyskinesia of the sphincter of Oddi in patients with persistent pain following a cholecystectomy. Sphincter stenosis is diagnosed by an elevated basal sphincter pressure, and these patients are often cured of their symptoms by an endoscopic sphincterotomy. Other manometric abnormalities have been identified, such as rapid phasic contractions, excessive retrograde contractions, and a paradoxical response to cholecystokinin, but their clinical relevance is not yet clear. Manometry in conjunction with peroperative cholangiography can detect small stones in the bile duct, but the technique is time-consuming and difficult to perform accurately. It is not much used.

 

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