The biliary tract

Pathological conditions

 

Gallbladder

Gallstone disease

Stones or concretions frequently occur in the gallbladder. Clinically the stones do not occur in isolation, but form part of an entity, gallstone disease. Stones occur about twice as frequently in women as in men. The majority of stones are cholesterol stones and less than 10% are pigment stones. Approximately 15-20% of calculi contains calcium and can be seen on a plain radiograph (Fig. 22). US is the primary method for identifying gallstones. A stone is seen as a rounded, echodense structure, with a typical acoustic shadow behind it (Fig. 23). Sometimes, especially if the gallbladder is small and deformed, only the acoustic shadow is seen, the stone itself being difficult to visualize. There are a multitude of US features associated with the presence of gallbladder stones and the accuracy of detection of stones on US is very high, approximately 95-98%. In contrast, stones in the extrahepatic bile ducts may be difficult to visualize on US, bowel gas often interfering with interpretation. Oral cholecystography has traditionally been regarded as one of the most accurate radiological methods so far as the diagnosis of gallstones is concerned but its accuracy is only 85-90%. Gallstones are seen in the contrast-filled gallbladder as dark filling defects (Fig. 24). The drawback with

	Figure 22. Gallstones containing calcium may be seen on a plain film, without contrast medium. Here several gallstones are seen as a row of white circles on an abdominal overview roentgenogram.
	Figure 23. US of a gallstone. The gallbladder (gb) is seen as a dark, echo-free cystic structure. It contains a stone (arrow) giving distal acoustic shadow ing (arrowheads).

cholecystography is that a diseased gallbladder does not concentrate contrast medium, which means that in circumstances in which the gallbladder wall is inflamed or fibrotic, or the cystic duct obliterated, the organ

	Figure 24. Cholecystogram showing multiple gallstones, which are seen as filling defects in the contrast-filled gallbladder.
	Figure 25. Floating gallstones, seen as a layer of filling defects in the contrast-filled gallbladder with the patient erect.

remains unopacified. Ultrasound is not dependent upon contrast medium concentration and demonstrates calculi irrespective of the presence of other gallbladder disorders. Plain film or CT scanning may give some clues as to the likely composition of stones. Cholesterol stones are usually uncalcified but if calcium is present it often occurs as a ring-like structure in the stone. In pigment stones the calcium is usually centrally located. Cholesterol stones may be lighter than the contrast-filled bile

Figure 26. US of acute cholecystitis. The gallbladder (arrows) is filled with echogenic biliary sludge, and there is a stone (arrowhead) giving an acoustic shadow.

and may thus be "floating" on oral cholecystography; they may also form a layer in the contrast-filled gallbladder, which is seen when a film is exposed with the patient in the upright position (Fig. 25). In cholesterol stones gas- filled fissures may be seen as dark linear structures - the so-called Mercedes- Benz sign.

Cholecystitis
Cholecystitis may be acute or chronic. Acute cholecystitis used to be a diagnosis in which imaging was unhelpful. Peroral cholecystography could only show that the gallbladder was "non-functioning" as the inflamed organ does not concentrate oral contrast medium. Fortunately, the situation is now very different.

Ultrasound has become the primary method for imaging acute cholecystitis, because the technique demonstrates not only the gallbladder wall and its contents, but also the adjacent tissues (Fig. 26). On US an inflamed gallbladder wall appears thicker than normal (over 3 mm) and with good technique even the various layers of the wall may be identified. Other diseases such as pancreatitis and liver disease, however, may also cause thickening of the bladder wall. Changes in the surrounding tissues may include oedema or fluid collections. On US the organ can be palpated under visual control, and may be tender, the so-called "ultrasound Murphy's sign". The gallbladder often contains gallstones (present in 90-95 % of cases) or sedimentation of its contents ("sludge"), but

	Figure 27. Porcelain gallbladder. The walls of the gallbladder are calcified, and visible on the plain film without contrast medium; this phenomenon may be seen as a sequela to chronic cholecystitis.
	Figure 28. Limey-bile. As a sequel of chronic cholecystitis, the gallbladder may contain calcified biliary "sludge", which is here visible on a plain film, without the patient having taken contrast medium.

these are non-specific findings which may occur in the absence of cholecystitis. Conversely, in so-called acalculous cholecystitis, stones are not present although the other signs of acute cholecystitis described above are often present. CT may show the same findings as US and though the information given by CT is often not as detailed and precise as that given by ultrasound, any changes present in the surrounding tissues may be

Figure 29. US of the gallbladder. The gallbladder wall is thicker than normal and slightly uneven. There are several rounded polypoid structures (arrows) arising from the bladder wall and protruding into the bladder lumen. These structures do not show any acoustic echo. The findings are compatible with hyperplastic cholecystosis.

better shown on CT. A radionuclide study performed with 99m Tc-HIDA may show non-activity over the gallbladder, as a sign of cystic duct obstruction.
As a sequela to chronic cholecystitis, the gallbladder wall may calcify and appear on the plain film as a so-called "porcelain gallbladder" (Fig. 27). For the same reason the organ may contain calcified "sludge" which is also visible on the plain film, i.e. "limey bile" (Fig. 28).

Hyperplastic cholecystoses

Cholesterolosis and adenomyomatosis belong to a group of disorders termed the hyperplastic cholecystoses, which share the feature of polypoid lesions of the gallbladder wall. The term cholesterolosis implies the presence of polypoid deposits of cholesterol in the bladder mucosa ("strawberry gallbladder"). In adenomyomatosis there are epithelial mucosal sinuses ("Rokitansky-Aschoff sinuses") extending between polypoid formations of localized muscular hypertrophy; these sinuses may vary greatly in size from the minute to the very large. If the polyps are bigger than 1 mm, they will show on both ultrasound and peroral cholecystography as typical lesions protruding from the surface of the wall into the bladder lumen (Fig. 29). Larger polyps may be difficult to distinguish from stones, but stones usually move with changes in posture

a

Figure 30. Gallbladder carcinoma. (a) US of the gallbladder. There is an exophytic growth of a lobulated tumour (*) into the gallbladder (gb), with infiltration of the tumour beyond the gallbladder wall. This tumour did not move with changes in posture. These features are suggestive of gallbladder carcinoma. (b) CT of the same patient shows the tumour (arrow) extending into the gallbladder. Possible tumour infiltration into the surrounding liver cannot be visualized even on this contrast-enhanced CT scan.

b

whereas polyps do not. Furthermore, on US there is no acoustic shadow behind a polyp.

Gallbladder carcinoma

Gallbladder carcinoma is relatively rare, seen in approximately 0.1 % of
patients with gallstones. On US a carcinoma may be seen as a space-occupying lesion in the gallbladder area, as a hypo-echoic mass within the gallbladder, or as a generalised thickening of the bladder wall (Fig. 30). It is important to note any extension of the tumour into the surrounding

Figure 31. Intravenous eholangiography (tomography) shows dilated extrahepatie biliary duets. Distally in the eholedoehal duet an obstrueting eoneretion is seen as a filling defeet (arrows).

tissues but this may be difficult to define on US. Peroral cholecystography is not usually helpful, because of non-visualization of the gallbladder. CT may show similar changes to ultrasound but usually demonstrates the extent of the tumour better than the latter technique and should always be obtained in order to assess the potential operability of the lesion.

Biliary duct disease

Gallstones in the extra-hepatic biliary ducts are difficult to evaluate by US, which has an accuracy of 20-50% in this examination. The biliary tree is difficult to visualize throughout its length and the common bile duct in particular may be obscured by bowel contents and gas. A sto ne in a normal duct, under 6 mm, may be difficult to discem, whereas a stone in a dilated duct is easier to see. In non-diagnostic or doubtful cases contrast media studies such as intravenous cholangiography (Fig. 31), ERC or PTC should be undertaken. Thin-slice computed tomography may also be helpful but without oral contrast medium (which may obscure a calculus in the lower common bile duct).

Peroperative and postoperative cholangiography is performed to rule out or diagnose residual stones in the biliary ducts (Fig. 32). Stenosis or obstruction of the extrahepatic ducts is sometimes seen as a consequence of trauma occurring during abdominal operations involving the biliary

a	Figure 32. (a)Peroperative needle cholangiography reveals multiple sto nes in the extrahepatic  biliary ducts, seen as roundedfilling defects. The needle is marked by arrows. (b)Postoperative T-tube cholangiography reveals several residual sto nes in the intra  and extrahepatic biliary ducts (arrows). The T-tube is marked by arrowheads.
b

tree, such as a cholecystectomy (Figs. 33,34). Most obstrueting lesions are, however, tumours (fig. 35), principally carcinoma of the head of the panereas. Sclerosing cholangitis causes multiple strietures in both the intra- and extrahepatic ducts (Fig. 36). In Caroli's disease there are ectatic dilatations ofthe intrahepatic ducts. A choledochal cyst shows as an area of dilatation of the distal choledochal duct (Fig. 37). All these changes are best shown on endoscopic or percutaneous cholangiography.

Figure 33. Endoscopic retrograde cholangiography. Contrast medium has been introduced in a retrograde fashion through cannulation of the papilla of Vater. The endoscope is seen in the picture. There is a post-operative stricture in the hepatic duct (arrow) and a stone (arrowheads) is seen as a filling defect in the dilated biliary ducts above the stricture.

a	Figure 34. A patient who had undergone a previous transduodenal papillotomy, presented with jaundice and epigastric pain. (a) Ultrasonogram, showing dilated intrahepatic biliary ducts, seen as dark, branching streaks in the liver parenchyma. (b) Endoscopic retrograde cholangiography demonstrates dilated intra- and extrahepatic biliary ducts and a very tight narrowing of the distal sphincter area. At autopsy purulent cholangitis was diagnosed, the common bile duct measured 3 cm in diameter and had a fibrotic narrowing at its distal end, extending for 3 cm above the papilla of Vater.
b

David J. Allison and Carl-Gustaf Standertskjold-Nordenstam