Human Anatomy Part 1 - K. A. Dyubenko, A. K. Kolomiytsev, Yu. B. Chaykovsky 2002

Special Part
Splanchnology, splanchnologia [the study of viscera] - Major digestive glands
Extrahepatic bile ducts - Radiography of the gallbladder and biliary tract

The following extrahepatic ducts are distinguished:

- the common hepatic duct, which is formed by the union of the right and left hepatic ducts;

- the cystic duct, which drains Bile from the Gallbladder;

- the common bile duct, formed by the convergence of the common hepatic and cystic ducts (Fig. 262).

The common hepatic duct, ductus hepatis communis, is formed by the union of the right and left hepatic ducts, ductus hepatis dexter et sinister, in the right half of the porta hepatis, anterior to the bifurcation of the portal vein. In adults, the length of the common hepatic duct is 2.5–3.5 cm, and its diameter is 0.3–0.5 cm. It runs within the hepatoduodenal ligament, lig. hepatoduodenale, and joins the cystic duct to form the common bile duct, ductus choledochus [biliaris].

The cystic duct, ductus cysticus, originates from the neck of the gallbladder. Its length averages 4.5 cm, and its diameter is 0.3–0.5 cm. The duct runs from right to left, upward and forward, and merges with the common hepatic duct at an acute angle. The muscular coat of the cystic duct consists of two layers: longitudinal and circular. The mucous membrane forms a spiral fold, plica spiralis (Heisteri) (see Fig. 258B). The mutual arrangement of the cystic and common hepatic ducts varies considerably, which must be taken into account during biliary surgery (see Fig. 259).

The common bile duct, ductus choledochus [biliaris]¹ (see Figs. 257, 258, 262), is formed by the union of the cystic and common hepatic ducts and runs within the hepatoduodenal ligament, lig. hepatoduodenale, to the right of the proper hepatic artery. Its length is 6–8 cm. The common bile duct joins the pancreatic duct and opens on the posterior wall (middle third) of the descending part of the duodenum at the major duodenal papilla, papilla duodeni major (Vater) (see Fig. 262). At the junction of the ducts, a dilation is formed—the hepatopancreatic ampulla, ampulla hepatopancreatica [biliaropancreatica]. There are several types (variants) of the relationship between the common bile duct and the pancreatic duct at their sites of opening into the duodenum (Fig. 263). The ducts may open onto the major duodenal papilla without forming an ampulla (Fig. 263A) or, uniting, form an ampulla (Fig. 263B). Within the hepatopancreatic ampulla, There is a partial or complete septum (Fig. 263C, D). There are also variants where the common bile duct and the accessory pancreatic duct, ductus pancreaticus accessorius (Fig. 263E), open independently. These anatomical variations in the relationship between the common bile duct and the pancreatic duct are of great importance in disorders of BILE AND PANCREATIC juice outflow into the duodenum.

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Fig. 262. Extrahepatic bile ducts. Division of the common bile duct into segments (schematic) (after K. Dyubenko):

1 - supraduodenal segment; 2 - retroduodenal segment; 3 - retropancreatic segment; 4 - intramural segment

¹ Recently, there has been a tendency to omit the word "common" from this term (A. Ham, D. Cormack, 1983).

In the wall of the duct just before the ampulla lies the sphincter of the choledochus, m. sphincter ductus choledochi, or Boyden's sphincter (PNA), while in the wall of the hepatopancreatic ampulla lies the second sphincter, m. sphincter ampullae hepatopancreaticae s. sphincter (Oddi)¹.

Fig. 263. Variations in the opening of the common bile duct and pancreatic duct into the duodenum (after Testut with additions) (A - E):

1 - duodenal mucosa; 2 - ductus choledochus; 3 - ductus pancreaticus; 4 - caput pancreatis; 5 - papilla duodeni major; 6 - papilla duodeni minor; 7 - sphincter Oddi; 8 - ampulla hepatopancreaticae

Contraction of the powerful Boyden's sphincter, which restricts the pre-ampullary part of the common bile duct, blocks the outflow of bile into the duodenum, causing bile to flow through the cystic duct into the gallbladder. The sphincters are under METABOLISM/18.html">The Influence of autonomic innervation and regulate the passage of bile (hepatic or cystic) and pancreatic juice into the duodenum. Digestive Hormones (cholecystokinin-pancreozymin), produced in the mucosa of The Stomach and Large Intestine, also participate in The regulation of bile excretion. Along with the Anatomical Features of the extrahepatic bile ducts, The sequence of bile discharge into the duodenum is of great importance. It is known that when the sphincter of the common bile duct relaxes, bile from the gallbladder (cystic bile) is discharged first, followed by lighter bile (hepatic bile) that filled the biliary ducts. The sequence of bile outflow underlies the Diagnosis and Treatment (duodenal sounding) of inflammatory processes in the bile ducts. In clinical (surgical) practice, the common bile duct is divided into four parts (segments) (see Fig. 262): supraduodenal (located above the duodenum in the lig. hepatoduodenale); retroduodenal (located behind the superior part of the duodenum, pars superior duodeni); retropancreatic — 2.9 cm (located behind the HEAD of the Pancreas², and sometimes within its parenchyma); and intramural (located in the posterior wall of the pars descendens duodeni).

X-ray Anatomy of the Liver. During radiological examination, the liver is visualized as a shadow corresponding to its position. Nowadays, ultrasound (US) and X-ray Computed Tomography (CT) make it possible to determine the size, shape, and Structure of these Organs. In clinical practice, cholangiography (using contrast agents) is used to visualize the biliary tract, gallbladder, and the presence of calculi within them.

On radiographs, the liver presents a dense, homogeneous shadow. The contour of the diaphragmatic surface of the liver merges with the shadow of the right dome of the Diaphragm. The outer and anterior contours of the right lobe of the liver are smooth and sharp. The inferior contour of the liver corresponds to its anterior margin — it extends downward and outward from the shadow of THE Vertebral Column, showing an indentation in the region of the porta hepatis and the gallbladder fossa. The inferior contour forms an acute angle not exceeding 60°.

In adults, the left lobe of the liver is projected onto the shadow of the Vertebral Column and is therefore visible mainly in the left lateral projection, where the shadow has a triangular shape with its base facing the anterior slope of the diaphragm, one side facing the anterior abdominal wall, and the other facing the anterior wall of the stomach. In children, the left lobe of the liver is large, and its shadow lies to the left of the vertebral column image.

¹ R. Oddi (Oddi R; 1864–1913) was an Italian surgeon who worked at the Department of Physiology at the University of Perugia.

² The retropancreatic part of the ductus choledochus can be compressed by a malignant tumor (Cancer of the head of the pancreas) and typically leads to obstructive jaundice (O. O. Shalimov).

Images of the liver in a plane perpendicular to the longitudinal axis of the body are obtained using computed tomography (see "Computed Tomography").

Ultrasound examination (US) of the liver. Ultrasound examination of the liver is performed by sequential scans (slices) in various planes. Since the greater part of the liver is covered by the Ribs, the examination is carried out through ultrasound-accessible "windows". These are primarily the right hypochondriac and epigastric regions.

Echo-anatomically, the liver is divided into two lobes: the right, which is larger, and the left, which is smaller. The falciform ligament serves as the boundary between the right and left lobes. On sonograms, it appears as a narrow echopositive band. In its anterior part lies a fibrous cord — the round ligament of the liver, which appears on sonograms as a hyperechoic oval or round structure. On horizontal slices, the liver is wedge-shaped. Its superior surface corresponds to the diaphragmatic dome, and its inferior surface is slightly concave. On the Inferior surface of the liver, There are two longitudinal grooves and one transverse groove. According to S. L. Hagen-Ansert (1976), the true dimensions of the liver are: transverse — 20–22.5 cm; vertical of the right lobe — 15–17.5 cm; anteroposterior (at the level of the upper pole of the right Kidney) — 10–12.5 cm.

Normally, the liver contour is sharp and smooth. Its anterior surface is convex, and the posterior is concave. The hepatic parenchyma is normally homogeneous, well-conducting to sound, and contains numerous fine- and medium-sized echo structures generated by Blood Vessels, ligaments, and large bile ducts. The Branches of the portal vein are always clearly visualized and run parallel to the anterior abdominal wall. The hepatic Veins are arranged fan-like at an angle to the anterior abdominal wall. The hepatic Arteries are identified over a short segment, directly near the porta hepatis. They appear as small tubular structures with a diameter of 1–1.5 mm, running parallel to the right and left branches of the portal system. Intrahepatic ducts are normally not visualized, except in the region of the porta, where the right and left hepatic ducts converge.

Computed tomography (CT) of the liver. CT of the liver allows for the visualization of the entire organ from its upper boundary (the diaphragmatic dome) to the tip of the caudate lobe. Scans are performed following the administration of a contrast agent. Computed tomography makes it possible to determine the liver's size and contour, visualize its blood vessels, and generate three-dimensional reconstructions essential for examining complex anatomical regions, such as the porta hepatis.

On computed tomograms, the liver exhibits distinct contours and a homogeneous structure (Fig. 264). Blood vessels appear as areas with a low attenuation coefficient compared to the hepatic parenchyma. The right and left lobes are clearly demarcated. The shape of the liver varies depending on the slice level on the tomogram. At the Th XII level, the liver has an indefinite shape, with the bulk of the organ represented by the right lobe. It occupies the greater part of the Abdominal cavity; its right contour is convex, while its inferior contour is concave and irregular. In the anterior sections of the scan, to the left of the midline, the gastric fundus is identified, located beneath the left dome of the diaphragm. At the Th X–XI level, the left lobe of the liver begins to appear, separated from the right lobe by the falciform ligament. The upper boundary of the liver passes through the right diaphragmatic dome and corresponds to THE POSITION OF the IX–X thoracic vertebrae. Most blood vessels are represented by the hepatic veins and branches of the portal vein, which is identified at the Th XII–L I level. A cross-section of the INFERIOR VENA CAVA is visible along the posterior edge of the liver. In most cases, the gallbladder is clearly visualized on tomograms as a round or oval low-density structure. Normally, the bile ducts are not visualized on tomograms.

Fig. 264. Computed tomogram of the abdominal cavity at the level of the liver, stomach, and Spleen (according to O. Ivankov):

1 - right hepatic lobe; 2 - left hepatic lobe; 3 - gastric fundus; 4 - caudate lobe of the liver; 5 - stomach; 6 - Abdominal Aorta; 7 - spleen; 8 - twelfth thoracic vertebra

Currently, special artificial diagnostic Methods—cholecystography and cholangiocholecystography (cholecystography)—are used to evaluate the functional state of the gallbladder and the patency of the bile ducts. In these Procedures, contrast agents (iodine compounds such as biliotrast, bilignost, biligrafin, etc.) are administered orally, intravenously, or introduced via a fibroscope into the orifice of the common bile duct through the major duodenal papilla (ampulla of Vater) to achieve duct opacification. Intravenous administration relies on the liver's ability to excrete iodine-containing compounds from the bloodstream into the bile; this method is known as excretory cholecystography. The oral method is based on the capacity of The Liver and gallbladder to uptake and concentrate the administered contrast agents.

Radiographs taken after cholecystography are used to examine the position, shape, contours, and STRUCTURE OF THE gallbladder shadow (Fig. 265). To assess the functional state of the gallbladder, its distensibility and motility are evaluated by comparing its dimensions on images taken before and after a cholecystokinetic stimulus.

Fig. 265. Retrograde cholangiopancreatography (according to O. O. Shalimov)

Cholecystography helps detect gallbladder anomalies (regarding position, number, shape, and structure). Positional Anomalies of the gallbladder are diverse; it may be located on the inferior surface of the left lobe of the liver, in the transverse fissure, or at the site of the round ligament. The most frequent shape anomalies include septations and kinks; occasionally, it resembles a "Phrygian cap" (M. D. Syomiy).

Radiographs obtained following intravenous excretory cholangiopancreatography (cholecystography) allow for the Determination of the position, shape, diameter, contours, and structure of the intra- and extrahepatic bile ducts (Fig. 266). Subsequently, the time of appearance of contrast-enhanced bile in the gallbladder neck is determined. Tomography of the bile ducts is often utilized during cholecystography to precisely determine the diameter, shape, and condition of the distal common bile duct, as well as the presence of calculi.

Fig. 265. Retrograde cholangiopancreatography (according to S. O. Shalimov) (Continued)

Fig. 266. Retrograde cholangiopancreatography (according to O. O. Shalimov)

Cholecystography can reveal various anomalies in the position of the bile ducts and the cystic duct. The number of bile ducts is also subject to variation (L. D. Lindenbraten, 1980).

Ultrasound examination (Ultrasonography) of the gallbladder. Longitudinal scanning of the gallbladder is performed at an angle of 20–30° relative to the sagittal axis of the body. Transverse scanning is carried out by moving the transducer from the xiphoid process of the Sternum toward the umbilicus. Normally, on a longitudinal scan, the gallbladder appears as a sharply contoured echo-negative structure free of internal echoes. It may be pear-shaped (pyriform), ovoid, or cylindrical, and is located in the right upper quadrant of the abdomen (right hypochondriac region). On transverse and oblique scans, the gallbladder appears round or ovoid. The fundus, which is its widest part, lies anterior and lateral to the neck.

Fig. 266. Retrograde cholangiopancreatography (according to O. O. Shalimov)

The neck is directed toward the porta hepatis—that is, posteriorly and medially. A distinct bend is typically observed at the junction of the body and the neck. Gallbladder dimensions vary across a wide range: length spans from 5 to 12 cm, width from 2 to 3.5 cm, and wall thickness is approximately 2 mm. In children, the Cytology/practical/108.html">Fundus of the gallbladder rarely extends beyond the inferior edge of the liver. In adults and the elderly, it may be positioned 1–4 cm lower, and in advanced age, it can project by up to 6 cm (I. S. Petrova, 1965). Ultrasonography of the gallbladder is performed to detect Developmental Anomalies and diagnose various pathologies (such as cholelithiasis, empyema, and cholesterosis). According to David J. Allison et al., ultrasound evaluation of the gallbladder yields an accuracy of 90–95%.

Computed Tomography (CT) of the Gallbladder and Bile Ducts

Computed tomography allows for the Differentiation of the gallbladder and the biliary tree without prior administration of radiopaque contrast agents. The gallbladder is visualized as a rounded or oval structure located adjacent to the medial margin of the right hepatic lobe or embedded within the parenchyma of the right lobe along its medial border. The cystic duct is identified only fragmentarily, which precludes a precise determination of its junction with the common bile duct. In less than 30% of healthy individuals, CT can visualize portions of the intra- and extrahepatic bile ducts. Extrahepatic bile ducts appear on tomograms as round or oval cross-sections with a diameter of 7 mm.

Blood supply to the extrahepatic bile ducts is provided by numerous branches of the proper hepatic artery. Venous drainage from the duct walls occurs into the portal vein.

Lymphatic drainage from the bile ducts proceeds via Lymphatic vessels running alongside the ducts and empties into the hepatic Lymph Nodes situated along the portal vein.

Innervation of the bile ducts is supplied by branches of the hepatic plexus (plexus hepaticus).