The reliability and clinical limitations of sonographic scanning of the biliary ducts

Sonographic scanning of the biliary ducts has been successfully used as a screening test to distinguish between patients with surgical and medical jaundice, with an accuracy of 90%. However, there is no consensus in the literature on what numerically defines a dilated biliary duct. To clarify this problem a prospective study of 102 consecutive patients was initiated to determine the sonographic size range of bile ducts in patients with and without extrahepatic ductal obstruction. The ultrasonic measurements were compared with direct measurements of the common bile duct, at surgery. The extrahepatic ductal system was visualized sonographically in 62% of the patients, while the intrahepatic ducts were found in 81% of the population. Direct measurements at operation agreed with the ultrasonic measurements in 84% of the patients. Analysis of the size range of the biliary ducts in patients with and without extrahepatic obstruction, by chi square analysis and the Student's t-test, allowed the following guidelines to be established. Extrahepatic bile duct obstruction was present if the extrahepatic bile ducts was 1 cm or wider (p less than 0.001) or if the intrahepatic bile duct was in excess of 0.5 cm (p less than 0.001). Similarly if the extrahepatic bile duct measured less than 0.8 cm sonographically, and the intrahepatic bile duct was 0.4 cm or less than bile duct, obstruction was not present (p less than 0.001).

Measurement of the endoscopic retrograde cholangiogram

The diameters of the common hepatic and bile ducts were measured in 100 endoscopic retrograde cholangiograms, and the effect of magnification was determined. Duct diameters were magnified by up to 48%. They were increased in some patients with chronic pancreatitis and after cholecystectomy, but were sometimes normal in patients with extrahepatic biliary obstruction.

The discrepancy between radiographic and sonographic bile-duct measurements

The upper limit of the normal bile-duct diameter is significantly smaller by ultrasound than that generally accepted for radiographic techniques. This appears to be due to (a) radiographic magnification, (b) ultrasonic underestimation, (c) a possible choleretic effect of radiographic contrast material, and (d) the fact that different regions are measured with different techniques. The diameter of the common hepatic duct was measured by ultrasound in 30 patients prior to and during intravenous cholangiography, and these measurements were correlated with each other and with the radiographic measurement. In vitro studies were also performed. It was found that the choleretic effect significantly increased duct size in a small percentage of cases. The radiographic magnification was a factor of 1.3, and the ultrasonic diameter was about 1.5-2.0 mm too small. Perhaps the most important cause of the discrepancy was measurement of different regions with different techniques.

Visualization of normal biliary ducts with ultrasound

Portions of the normal biliary ducts, the main left and right hepatic ducts, common hepatic duct and the common bile duct can be regularly demonstrated with static ultrasound equipment. This was achieved in 94% of patients in this series, when a positive search was made for the ducts. The normal common duct measured between 2 mm and 5 mm in 126 patients in this series in whom it was visualized.

The size of the normal common hepatic duct following cholecystectomy: an ultrasonographic study

Sixty-seven asymptomatic patients underwent repeat ultrasonography four to 16 months following cholecystectomy with or without common bile duct exploration. Fifty-six patients (84%) had common hepatic ducts with a normal internal diameter of 4 mm or less. Four patients had common hepatic ducts measuring 5 mm, and seven patients had common hepatic ducts measuring 6 to 10 mm. It is concluded that, although the common hepatic duct generally is not dilated following cholecystectomy, there is a significant minority (16%) of asymptomatic patients who have common hepatic ducts larger than 4 mm, and in these patients the duct may measure up to 10 mm.

Demonstration of the normal extrahepatic biliary tract with computed tomography

When optimum computed tomography (CT) technique and computed angiotomography are utilized, the normal extrahepatic biliary ducts (equal to or less than 6 mm in diameter in patients without cholecystectomy) can be demonstrated in approximately 30% of clinical scans. Measurement of the anteroposterior diameter of the bile duct is more accurate than recording the transverse diameter, since the apparent transverse dimension will vary depending on the orientation of the duct in the plane of section. Phantom studies indicate that the absolute error of measurement is approximately one pixel diameter irrespective of duct diameter. The normal and abnormally dilated extrahepatic biliary ducts should be distinguished with CT.

Subsegmentation of the human liver

Subsegmental patterns in 85 human livers have been studied after preparing corrosion casts of the hepatic duct, hepatic artery and portal vein by injecting coloured butyl butyrate solution. A subsegment was identified by the independence of its vessels and ducts from those of its neighbours. In the present study nine hepatic subsegments have been observed: (1) posterior superior, (2) posterior inferior, (3) anterior superior, (4) anterior inferior, (5) medial superior, (6) medial inferior, (7) lateral superior, (8) lateral inferior, (9) caudate (the caudate lobe and process form a spearate subsegment on the basis of the pattern of their blood supply and biliary drainage). The sizes of the subsegments were very similar in 41 cases (48.23%). In the others, some increase or decrease in the size of one or more subsegments at the expense of neighbouring subsegments was observed. These variations are illustrated.

Measurement of biliary tract size and drainage time. Comparison of endoscopic and intravenous cholangiography

Measurements of biliary tract size and drainage time were made in 23 patients following endoscopic retrograde cholangiopancreatography (ERCP) and intravenous cholangiography (IVC). The extrahepatic biliary tree appeared approximately 3 mm larger on ERCP than on IVC. Serial measurements of the biliary tree comparing IVC with ERCP are subject to this difference. Comments regarding increasing dilatation of the biliary tree could be erroneous if these differences in technique are ignored. The biliary tract should be free of contrast medium 45 minutes after filling on ERCP; if not, an abnormality may be present at the sphincter of Oddi, even in the absence of other gross radiological biliary tract pathology.

Intrahepatic vascular division in the pig: basis for partial hepatectomies

Transplantation of resected hepatic fragments, with the attendant vascular and biliary tract reconstruction, presents difficulties. We have studied the intraparenchymal vascular division in the pig with a view to performing partial hepatectomies with the greastest possible anatomical support. Forty-six molds of the various vascular territories were obtained from the 31 porcine livers. Each segment of the median lobe is dependent on the adjacent lateral lobe. Its intersegmental fissure is the obligatory site for parenchymal section to be continued through horizontal portion of portal vein, hepatic artery, and left hepatic duct. A right hemihepatectomy unfailingly results in the devitalization of the left side of the liver. If the goal of a hepatectomy is the transplantation of the resected fragment, it is recommended that the right side of the liver be utilized, as its more convenient extrahepatic vascular and biliary calibre will permit pedicular conservation and anastomosis.

[Surgical importance of the topography of the vessels and bile ducts in the hepatic portal in case of their atypical branching and formation]

The portal triad was studied on 100 specimens of porta hepatis, using the methods of preparation, roentgenography and corrosion. An unusual origin of hepatic arteries was observed in 36%, atypical formation of bile ducts--in 33%, and a specific branching of the portal vein--in 15%. Different variants of vessels and bile ducts related with their specific development can be intercombined. Due to it, during surgical procedures in the region of porta hepatis it is necessary to bear in mind not only an atypical structure of each element of the Glisson system, but also the possibility of frequent combination of their different variants.

Lesions of the segmental and lobar hepatic ducts

Despite reports to the contrary, unobstructed drainage of 50% of an otherwise normal liver through either the right or left uninfected hepatic duct is adequate to restore normal liver function, even if the obstructed lobe remains in place. An undrained liver lobe, if present, may require no further treatment. As long as it is completely obstructed and uninfected, it will undergo a progressive asymptomatic atrophy. Cholangitis invariably develops behind a partial lobar ductal obstruction, producing jaundice, pruritus, and fever. Unless unobstructed, uninfected biliary flow can be achieved through a segmental or lobar duct, it is better that the duct be completely obstructed and the affected liver parenchyma allowed to atrophy, provided there is normal biliary flow from the residual 50% of liver. This concept is important in the management of injured anomalous segmental or lobar hepatic duct and in the palliative treatment of bile duct carcinoma. Localized intrahepatic infections communicating with abnormal biliary ducts will require hepatic resection of the infected parenchyma and ducts for cure. The abnormality may be saccular dilatation of the intrahepatic ductal system with abscess formation or intrahepatic abscess associated with stenosis of the ductal system from trauma to the duct, to the duct and liver, or to retained intrahepatic stones. Diffusely situated intrahepatic abscesses secondary to ductal abnormalities can be treated with systemic antibiotics, local drainage of a dmoninant abscess, and efforts to improve biliary drainage.

Carcinoma of the extrahepatic biliary tract

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