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ANATOMICAL ABNORMALITIES OF THE LIVER

These are being increasingly diagnosed with more widespread use of CT and ultrasound scanning.
Accessory lobes. The livers of the pig, dog and camel are divided into distinct and separate lobes by strands of connective tissue. Occasionally, the human liver may show this reversion and up to 16 lobes have been reported. This abnormality is rare and without clinical significance. The lobes are small and usually on the undersurface of the liver so that they are not detected clinically but are noted incidentally at scanning, operation or necropsy. Rarely they are intrathoracic. An accessory lobe may have its own mesentery containing hepatic artery, portal vein, bile duct and hepatic vein.

This may twist and demand surgical intervention. Ectopic liver. Small nodules of normal liver derived from the embryologic hepatic bud may be found in less than 1% of laparoscopies and autopsies near the gallbladder, hepatic ligaments, gastrorenal ligament, omentum, retroperitorneum
and thorax. These may give rise to hepatocellular carcinoma.

Riedel’s lobe. This is fairly common and is a downward tongue - like projection of the right lobe of the liver.



It is a simple anatomical variation; it is not a true accessory lobe. The condition is more frequent in women. It is detected as a mobile tumour on the right side of the abdomen which descends with the diaphragm on inspiration. It may come down as low as the right iliac region. It is easily mistaken for other tumours in this area, especially a visceroptotic right kidney. It does not cause symptoms and treatment is not required. Rarely, it is a site for metastasis or primary hepatocellular carcinoma.

Scanning may be used to identify Riedel’s lobe and other anatomical abnormalities.
Cough furrows on the liver. These are vertical grooves on the convexity of the right lobe. They are one to six in number and run anteroposteriorly, being deeper posteriorly.

These represent diaphragmatic sulci and fissures produced by pressure exerted by diaphragmatic
muscle on peripheral structurally weak liver parenchymal zones associated with watershed vascular distribution. Chronic cough produces such pressure.

Corset liver. This is a horizontal fi brotic furrow or pedicle on the anterior surface of one or both lobes of the liver just below the costal margin. The mechanism is unknown, but it affects elderly women who have worn corsets for many years. It presents as an abdominal mass in front of and below the liver and is isodense with the liver. It may be confused with a hepatic tumour.

Lobar a trophy. Interference with the portal supply or biliary drainage of a lobe may cause atrophy. There is usually hypertrophy of the opposite lobe. Left lobe atrophy found at post - mortem or during scanning is not uncommon and is probably related to reduced blood supply via the left branch of the portal vein. The lobe is decreased in size with thickening of the capsule, fibrosis and prominent biliary and vascular markings. The vascular problem may date from the time of birth. Loss of
left lobe parenchyma in this instance develops by the process of ischaemic extinction due to impaired flow from the affected large portal vein branch. Replacement fibrosis ensues. This large vessel extinction process should be distinguished from cirrhosis in which the entire liver is affected by numerous intrahepatic and discrete extinction lesions, which affect small hepatic veins and portal vein branches during the course of inflammation and fibrosis. Hence, in cirrhosis the entire
liver surface is diffusely converted to regenerative parenchymal nodules surrounded by fibrosis.

Obstruction to the right or left hepatic bile duct by benign stricture or cholangiocarcinoma is now the most common cause of lobar atrophy. The alkaline phosphatase is usually elevated. The bile duct may not be dilated within the atrophied lobe. Relief of obstruction may reverse the changes if cirrhosis has not developed.

Distinction between a biliary and portal venous aetiology may be made using technetium - labelled iminodiacetic acid (IDA) and colloid scintiscans. A small lobe with normal uptake of IDA and colloid is compatible with a portal aetiology. Reduced or absent uptake of both isotopes favours biliary disease. Agenesis of the r ight l obe. This rare lesion may be an incidental finding associated, probably coincidentally, with biliary tract disease and also with other congenital abnormalities. It can cause presinusoidal portal hypertension. The other liver segments undergo compensatory
hypertrophy. It must be distinguished from lobar atrophy due to cirrhosis or hilar cholangiocarcinoma. Situs i nversus ( SI ). In the exceedingly rare SI totalis or abdominalis the liver is located in the left hypochondrium and may be associated with other anomalies including biliary atresia, polysplenia syndrome, aberrant hepatic artery anatomy and absent portal vein.
Hepatic surgery (partial hepatectomy, liver transplantation) is feasible, but complex. Other conditions associated with displacement of the liver from its location in surgeon planning a liver resection. There are wide variations in portal and hepatic vessel anatomy which can be demonstrated by spiral computed tomography (CT) and magnetic resonance imaging (MRI) reconstruction.

These are being increasingly diagnosed with more widespread use of CT and ultrasound scanning.
Accessory l obes. The livers of the pig, dog and camel are divided into distinct and separate lobes by strands of connective tissue. Occasionally, the human liver may show this reversion and up to 16 lobes have been reported. This abnormality is rare and without clinical signifi cance. The lobes are small and usually on the undersurface of the liver so that they are not detected clinically but are noted incidentally at scanning, operation or necropsy. Rarely they are intrathoracic. An accessory lobe may have its own mesentery containing hepatic artery, portal vein, bile duct and hepatic vein.
This may twist and demand surgical intervention. Ectopic l iver. Small nodules of normal liver derived from the embryologic hepatic bud may be found in less than 1% of laparoscopies and autopsies near the gallbladder, hepatic ligaments, gastrorenal ligament, omentum, retroperitorneum
and thorax. These may give rise to hepatocellular carcinoma.

Riedel’s l obe. This is fairly common and is a downward tongue - like projection of the right lobe of the liver.

It is a simple anatomical variation; it is not a true accessory lobe. The condition is more frequent in women. It is detected as a mobile tumour on the right side of the abdomen which descends with the diaphragm on inspiration. It may come down as low as the right iliac region. It is easily mistaken for other tumours in this area, especially a visceroptotic right kidney. It does not cause symptoms and treatment is not required. Rarely, it is a site for metastasis or primary hepatocellular carcinoma.
Scanning may be used to identify Riedel’s lobe and other anatomical abnormalities.

Cough f urrows on the l iver. These are vertical grooves on the convexity of the right lobe. They are one to six in number and run anteroposteriorly, being deeper posteriorly.

These represent diaphragmatic sulci and fissures produced by pressure exerted by diaphragmatic
muscle on peripheral structurally weak liver parenchymal zones associated with watershed vascular distribution. Chronic cough produces such pressure.

Corset liver. This is a horizontal fi brotic furrow or pedicle on the anterior surface of one or both lobes of the liver Anatomy and Function 5 less than 11 mm, although after cholecystectomy it may
be more in the absence of obstruction.

The duodenal portion of the common bile duct is surrounded by a thickening of both longitudinal and circular muscle fi bres derived from the intestine. This is called the sphincter of Oddi ( c . 1887).
The gallbladder is a pear - shaped bag 9 cm long with a capacity of about 50 mL. It always lies above the transverse colon, and is usually next to the duodenal cap overlying, but well anterior to, the right renal shadow. The fundus is the wider end and is directed anteriorly; this is the part palpated when the abdomen is examined. The body extends into a narrow neck which continues into the cystic duct. The valves of Heister are spiral folds of mucous membrane in the wall of the cystic duct and
neck of the gallbladder. Hartmann’s pouch is a sacculation at the neck of the gallbladder; this is a common site for a gallstone to lodge.

The mucosa is in delicate, closely woven folds; instead of glands there are indentations of mucosa which usually lie superfi cial to the muscle layer. Increased intraluminal pressure in chronic cholecystitis results in formation of branched, diverticula - like invaginations of the mucosa which reach into the muscular layer, termed Rokitansky – Aschoff sinuses. There is no submucosa or
muscularis mucosae. The gallbladder wall consists of a loose connective tissue lamina propria and muscular layer containing circular, longitudinal and oblique muscle bundles without defi nite layers, the muscle being particularly well developed in the neck and fundus. The outer layers are the subserosa and serosa.

The distensible normal gallbladder fi lls with bile and bile acids secreted by the liver, concentrates the bile through absorption of water and electrolytes and with meals contracts under the infl uence of cholecystokinin (acting through preganglionic cholinergic nerves) to empty bile into the duodenum.
Blood s upply. The gallbladder receives blood from the cystic artery . This branch of the hepatic artery is large, tortuous and variable in its anatomical relationships.

Smaller blood vessels enter from the liver through the gallbladder fossa. The venous drainage is into the cystic vein and thence into the portal venous system. Attention to the vascular - biliary anatomy in the reference area known as Calot ’ s triangle (bordered by the cystic duct, common hepatic duct and lower edge of the liver) reduces the risk of vascular injuries and potential biliary strictures. Most bile duct injuries occur at cholecystectomy (incidence of < 1.3% for either open or laparoscopic
cholecystectomy). After liver transplantation 10 – 33% of patients may develop biliary complications, of which biliary stricture is the most important.

The arterial blood supply to the supraduodenal bile duct is generally by two main (axial) vessels which run the right upper quadrant include congenital diaphragmatic hernias , diaphragmatic eventration and omphalocoele.

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