Gallbladder and Bile Ducts

and Ian A. D. Bouchier²

(1)

Bishop Auckland, UK

(2)

Edinburgh, Midlothian, UK

Gallbladder stones form the majority of biliary disease, and are conveniently detected by ultrasonography (US).

After cholecystectomy; where the bile ducts are of especial interest; and where pancreatic evaluation is needed, contrast magnetic resonance (MRCP) is the best non-invasive test. CT has a lesser role.

Where therapeutic intervention is planned ERCP comes into its own, enabling sphincterotomy, stone extraction and stenting.

If there is direct access to the biliary tree then iodine contrast radiology and choledochoscopy have a place in finding stones and strictures.

EUS allows both imaging of the bile ducts and pancreas, with the possibility of fine needle aspiration cytology (FNA) of the pancreas.

Other techniques such as oral cholecystography and infusion cholangiography have a more restricted role nowadays.

Serum biochemistry may support a diagnosis, but is usually nonspecific. Studies of biliary physiology have not found their way into routine clinical practice. Duodenal drainage with examination of bile-rich fluid is seldom used in making a diagnosis of gallbladder disease, though in gallstone disease cholesterol crystals indicate cholesterol-rich stones, and microspheroliths indicate mineral/pigment stones.

15.1 Ultrasonography (Figs. 15.1 and 15.2)

High-definition real-time ultrasonic scanning is very rapid and simple to perform, and yields a 96% accuracy for gallbladder gallstones.

Gallstones >3 mm in size can be detected as mobile structures within the gallbladder, the wall of which is often thickened. Stones >5 mm in diameter produce prominent acoustic shadows which assist interpretation. The presence of calcium in stones increases the ultrasonic definition.

The thickness of the gallbladder wall may be a clue to disease. It is no thicker than 2 mm in 97% of asymptomatic subjects without gallstones and >3 mm thick in 45% of those with gallstone disease. Large carcinomas of the gallbladder are readily seen, as are mucocoeles.

Failure to obtain an image of the gallbladder is uncommon, but may also be a sign of disease.

Ultrasonography is useful for measuring bile duct calibre but is not as accurate as MRCP for detecting duct stones. It readily defines choledochal cysts in children. Ultrasonography can be employed at laparotomy using a transducer held adjacent to bile ducts and pancreas. This could replace the operative cholangiogram. Ultrasonic gallbladder scanning is very useful for evaluation of the nonfunctioning gallbladder or after a failed cholecystogram. High-definition real-time scanning has largely replaced the oral cholecystogram as a first-line test but the techniques are complementary.

Real-time scanning is used to study gallbladder motility and may well prove to be of value in the definition and diagnosis of ‘biliary dyskinesia’.

Fig. 15.1

Abdominal ultrasound showing normal gallbladder

Fig. 15.2

Abdominal ultrasound showing gallstone as an echogenic focus with acoustic shadowing

15.2 Magnetic Resonance Cholangiography (MRCP) (Figs. 15.3 and 15.4)

MRCP with contrast enhancement is now the standard test for bile duct and pancreatic disease. It is accurate and non-invasive. It is however claustrophobic and noisy, and not always tolerated by patients, when EUS or CT with torus scanners may be a better option.

Fig. 15.3

MRCP Normal bile ducts and gallbladder.Normal proximal pancreatic duct

Fig. 15.4

MRCP Multiple stones in dilated bile ducts. Absent gallbladder. Normal pancreatic duct

15.3 Endosonography (EUS)

This technique is not freely available at present, but offers the chance of detecting common bile duct stones without introducing iodine contrast directly into the biliary system. Biliary tumours and strictures can also be identified. It can be used as a screen preliminary to therapeutic ERCP.

15.4 Plain Radiology

Ten to twenty percent of gallstones are sufficiently calcified to be visible on the upper right side of the abdomen. Sometimes the calcification is homogeneous, but often it shows an internal laminar pattern which is helpful in diagnosis. Gallstones may either have rounded contours, or straight edges if they have been pressed against other stones. Multiple small irregular calcified stones are frequently composed of calcium bilirubinate. Pure cholesterol stones are radiolucent. Occasionally large gallstones show internal fractures with hyperlucent lines radiating from the centre. This is called the tri-fin or Mercedes-Benz sign and can be detected even in the absence of calcification. The position of gallstones usually requires confirmation by supplementary procedures.

Calcium deposits are occasionally seen in the gallbladder wall: the ‘porcelain gallbladder’. Even less frequently, bile contains a large amount of calcium salts in suspension: ‘limy’ or ‘milk of calcium’ bile, which outlines the biliary tree. Gas in the biliary tree occurs in infections with gas-forming organisms, called emphysematous cholecystitis. It also occurs when there is a fistula between the intestine and gallbladder or bile ducts and after some operations to the biliary tree.

Gas can also occur when there is an incompetent sphincter of Oddi, which may result from sphincteroplasty.

15.5 Oral Cholecystography (Figs. 15.5 and 15.6)

This remains a method of demonstrating gallstones in a functioning gallbladder, although it has now been superseded by ultrasonography. Oral cholecystography is less useful in acute cholecystitis when cystic duct obstruction occurs. Good results are obtained by experienced radiographers and the technique is economical of radiologists’ time.

15.5.1 Method

A plain radiograph of the abdomen is taken prior to oral administration of an opaque contrast medium. This is absorbed from the intestinal tract, excreted by the liver, concentrated in the gallbladder and discharged via the bile ducts into the intestine. A variety of tri-iodo organic iodine compounds may be used for this purpose: a popular agent is iopanic acid, six 500 mg tablets being with a normal evening meal. The patient then fasts until the radiographic examination the following day.

An alternative technique is to administer 6 g iopanic acid over 1–2 days prior to the examination. This may yield a higher proportion of positive results at the first examination.

Fig. 15.5

Oral cholecystogram showing floating gallstones

Fig. 15.6

Oral cholecystogram showing radiolucent gallstones

Some departments routinely administer a laxative with the preparation. As this may interfere with the absorption of the contrast medium, and as intestinal gas causes much more difficulty with interpretation than faeces, it cannot be recommended.

Radiographic films of the full gallbladder are obtained between 12 and 16 h after the ingestion of the opaque medium, in both erect and horizontal postures. If opacification is poor tomography is helpful. Gallbladder contraction is then stimulated by either a physiological stimulus such as eating two eggs, a cheese roll or a bar of chocolate, or by slow IV injection of cholecystokinin (CCK) 33 units. Larger doses of cholecystokinin and proprietary emulsions should not be used as they tend to cause abdominal distress and vomiting. Caerulin is an alternative pharmaceutical preparation but has no definite practical advantages. Further radiographic films are taken after gallbladder contraction, which occurs 30–60 min after an oral stimuli and 10–20 min after IV CCK.

Contraction films may show calculi which were not visible in the filled gallbladder, and at this stage it may be possible to visualize the cystic duct. The common bile duct is delineated clearly by oral cholecystography only occasionally. Failure of gallbladder function on cholecystography is not certain evidence for disease, and it is advisable to repeat the examination at least once. This may be undertaken conveniently after an initial series of films following a 3 g dose of iopanic acid by giving a further dose of 3 g iopanic acid on the day of the unsatisfactory examination and repeating the films the next day. Alternatively, some other test such as ultrasonography or infusion cholangiography should be undertaken.

15.5.2 Interpretation

Two definite appearances on oral cholecystogram provide unequivocal evidence of organic gallbladder disease. One is when there are gallbladder stones, and the other is the presence of contrast in the bile ducts but no gallbladder filling. Five percent of examinations yield evidence of some abnormality of the gallbladder wall such as cholesterolosis, adenomyomatosis, papillomas, prominent spiral valves and a Phrygian cap. These occur independently of gallstones and cholecystitis, and are not proof of symptomatic biliary disease.

Cholesterolosis of the gallbladder is suspected when there is an uneven mucosal contour with single or multiple filling defects. Adenomyomatosis of the gallbladder may show as a solitary filling defect, as a segmental stricture which must be distinguished from a ‘Phrygian cap’ (in which the septum is thinner and the distal segment contracts proportionately with the proximal segment) or as a diffuse condition which can be recognized by the contrast-filled Rokitansky-Aschoff sinuses. The gallbladder affected by cancer usually shows no function and generally contains stones.

A meticulous radiological technique is required for oral cholecystography: if this is achieved it is one of the most accurate of radiological investigations, detecting abnormalities with an accuracy of 95–99%. Positive evidence of gallstones is obtained in 70% of cases, and presumptive evidence is obtained in 98–99%. It probably detects 95% of significant cholecystitis.

Failure to outline the gallbladder also occurs if absorption of the contrast medium is impaired. This may result from vomiting, delayed gastric emptying and diarrhoea. In such circumstances no conclusions can be drawn regarding gallbladder function. Oral cholecystography is not undertaken when there is liver cell dysfunction, because no satisfactory excretion of the dye is obtained when the serum conjugated bilirubin concentration is >50μmol/I. Difficulty may also be encountered in anicteric patients with cholestasis. In the absence of parenchymal liver disease or hypermotility of the gut the failure to visualize the gallbladder after two attempts at cholecystography (the second being with a double dose of the contrast agent) may be accepted as evidence that the organ is diseased. The technique should be avoided in patients with renal failure, in whom it is often ineffective and also hazardous.

A problem which is sometimes encountered is the patient with classical biliary colic or acute relapsing pancreatitis in whom the oral cholecystogram is normal. In some of these cases ultrasonography (or repeat cholecystography) reveals stones. In cholecystitis without demonstration of gallstones on cholecystography, hyperlucent fat in the gallbladder wall may provide a clue to the diagnosis in about 50% of cases.

15.6 Operative Cholangiography

At the time of cholecystectomy the cystic duct is cannulated and iodine contrast such as diatrizoate is injected. Good images of the common duct and both hepatic ducts are obtained. This procedure eliminates the risk of unsuspected retained stones, which occur in up to 4% of patients after cholecystectomy. It also detects the rare hepatic and bile duct carcinomas. At present the consensus view is that operative cholangiography should be considered in all patients undergoing cholecystectomy for gallstones unless there has been careful pre-operative screening with MRCP. Digital subtraction techniques improve image quality. Both flexible and rigid choledochoscopes (cholangioscopes) are available for the same purpose; these usually require the common duct to be opened for their insertion and do not offer entirely satisfactory views of the distal common bile duct. Direct ultrasonography is another option.

Where duct stones have been removed it is usual to leave a T-tube in place and to confirm clearing of calculi by repeating the cholangiogram through the tube immediately before it is removed.

15.7 Percutaneous Transhepatic Cholangiography (PTC) (Figs. 15.7, 15.8, and 15.9)

This procedure can allow for precise localization of the cause of extrahepatic obstruction before abdominal surgery is undertaken. However, ultrasonography, EUS, MRCP and CT can often provide similar information and are less potentially hazardous.

15.7.1 Method

The patient is prepared as for a liver biopsy. It is important that a surgeon is informed when the procedure is to take place so that a laparotomy, if needed, can be performed without undue delay. Bile leakage and septicaemia may occur, even with the fine Chiba needle, and antibiotic cover starting immediately before the procedure is prudent. Gentamicin 80 mg IV is commonly used. Studies of blood haemostasis should be normal, as for liver biopsy.

The patient is placed supine on the radiology table and the procedure is carried out under fluoroscopy. The needle is 15 cm long, 0.7 mm external diameter and fitted with a stylet (Fig. 15.7). It is flexible so that the patient can breathe normally when it is in position.

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