Liver Diseases

Published on 16/04/2015 by admin

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13 Liver Diseases

Anatomy of the Liver

image

Liver in Situ

image

Surfaces and Bed of Liver

Basic Gross Anatomy

• Liver develops in ventral mesogastrium, surrounded by peritoneum, except for bare area bounded by

image Coronary ligament: peritoneal attachment to the inferior diaphragm
image Left and right triangular ligaments, where coronary ligament reflects posteriorly

• Falciform ligament: remnant of ventral mesogastrium attaching to the abdominal wall
• Round ligament

image Remnant of umbilical vein within the falciform ligament
image Persisting venous connections may be present between liver/portal system and body wall.

• Hepatoduodenal ligament: peritoneal fold surrounding portal triad (hepatic artery proper, portal vein, bile duct), right edge of lesser omentum
• Omental foramen (of Winslow): posterior to hepatoduodenal ligament, opens into lesser (peritoneal) sac
• Lesser omentum (hepatogastric ligament) and posterior aspect of stomach form anterior wall of lesser (peritoneal) sac

Divisions

image

Liver Segments and Lobes

• Right and left hepatic lobes: divided by a plane extending from cystic fossa (anteroinferior) through inferior vena cava (superoposterior)
• Right lobe typically contains 50%-70% of total liver volume.

image This is different from the historical view, dividing lobes by the falciform ligament.

• Each hemiliver contains its own hepatic artery branch, portal blood supply, venous drainage, and bile duct.

image Basis for dividing the lobes without total vascular inflow occlusion

• Further division into 8 segments, resectable based on blood vessel and bile duct anatomy

image Segment I: posterior, right and left caudate lobe
image Segment II: left lateral division, left portal lobe, lateral segment (lateral superior)
image Segment III: left lateral division, left portal lobe, left lateral anterior segment (lateral inferior area)
image Segment IV: medial division, left portal lobe, medial segment (medial inferior area, quadrate lobe)
image Segment V: right medial division, right portal lobe, left anterior medial segment (anterior inferior area)
image Segment VI: right lateral division, right portal lobe, lateral segment (posterior inferior)
image Segment VII: right lateral division, right portal lobe, posterior lateral segment (posterior superior)
image Segment VIII: right medial division, right portal lobe, posterior medial segment (anterior superior area)

Portal Triads and Bile Duct System

image

Liver Vessel and Duct Distribution

• Portal triads—hepatic artery, bile duct, and portal vein branches—and lymphatics seen in characteristic relationships from microscopic (lobular) to macroscopic (lobar) levels
• Popular functional concepts of liver parenchyma include classic lobules and liver acini organized around vessels.
• Interlobular portal vein branches travel in interlobular septum on periphery of hepatic lobules.
• Interlobular hepatic artery branches travel alongside portal veins in septa, providing smaller branches to ducts and parenchyma (hepatocytes) of lobules.
• Interlobular bile duct branches receive bile canaliculi draining lobular parenchyma.
• Central veins in the middle of lobules drain into hepatic vein tributaries.
• Sinusoids are formed by plates of hepatocytes surrounding lobular central veins.
image

Liver Structure Schema

Innervation of the Liver

• Visceromotor control of human liver parenchyma and intralobular biliary ductules

image Incompletely understood
image Efferents involved in regulation of portal blood flow, bile flow, regeneration of parenchyma, metabolism of lipids, carbohydrates, and plasma proteins

• Hepatic plexus (around the hepatic artery proper) is largest branch of celiac plexus.
• Parasympathetic: vagus

image Preganglionic fibers from anterior and posterior vagal trunks distributed via celiac plexus to intrahepatic ganglion cells
image Postganglionic fibers associated with intralobular parenchyma

• Sympathetic

image Preganglionic fibers from intermediolateral columns of T7-T10 segments via splanchnic nerves to celiac ganglion
image Postganglionic fibers from celiac ganglion cells to smooth muscle of interlobular blood vessels and ductules

• Afferent

image Segmental visceral afferents

image Travel back via splanchnic nerves to dorsal root ganglia and thoracic spinal segments T7-T10
image Mediate pain and reflexes

image Vagal afferents

image Ganglion cells in nodose (inferior vagal) ganglion
image Involved in hepatic regulatory mechanisms

image Phrenic nerves: mediate some pain
image Pain diffusely mapped

• Parasympathetic, sympathetic, and afferent fibers distributed with blood vessel branches to intralobular tissues

Vessels and Lymphatics

image

Celiac Artery Variations and Collateral Supply of Liver

Arterial Supply

• Branches highly variable
• Celiac artery branches

image Common hepatic artery

image Hepatic artery proper, right and left hepatic arteries
image Right gastric artery
image Gastroduodenal artery

image Left gastric artery

• Right hepatic artery arises from superior mesenteric artery in 10%-20% of patients.
• Left hepatic artery arises from left gastric artery in ~10% of patients.
• Rarely, common hepatic artery arises from superior mesenteric artery.
image

Hepatic Portal Vein Tributaries, Portocaval Anastomoses

Portal Venous Supply

• Contains no valves
• Formed by confluence of superior mesenteric vein (right portal) with splenic and inferior mesenteric veins (left portal)
• Right–left juncture usually occurs within hepatoduodenal ligament.
• Left portal drainage goes toward left (hemi) liver, from distal esophagus, lesser curvature of the stomach, spleen, body and tail of the pancreas, and distal half of colon.
• Right portal drainage goes toward right (hemi) liver, from duodenum, head of pancreas, jejunum, ileum, and first half of colon.
• Right- and left-sided drainage typically mixes in quadrate and caudate lobes.

Hepatic Venous Drainage

• Central veins of lobules drain into tributaries of hepatic veins.
• Intrahepatic right and left hepatic veins empty directly into inferior vena cava.
image

Lymph Vessels and Nodes of Liver

Lymphatic Drainage

• Posterior aspect of the liver drains toward phrenic nodes on centromedial inferior diaphragm or directly through caval hiatus to mediastinal nodes.
• Anterior lymphatic drainage flows toward porta hepatis, emptying to hepatic nodes clustered around hepatic artery.
• Hepatic and mediastinal nodes drain toward cisterna chyli and thoracic duct.

Clinical Correlates

Liver Functions

• Largest compound gland, principal metabolic and detoxification organ
• Hepatocytes synthesize glycogen from glucose and store and break down glycogen as needed.
• Liver synthesizes albumen (transport agent and osmotic agent in serum).
• Liver disease can lead to low serum albumen level and loss of water into peritoneal cavity (ascites).
• Liver secretes glucose, plasma proteins, and lipoproteins.
• Liver secretes bilirubin, immunoglobulin A (IgA), and bile salts.

Liver Trauma

• Organ most often involved in blunt and penetrating abdominal trauma
• Blunt trauma might not require surgical management.
• Penetrating trauma: surgery is the standard of care

Benign Tumors

• Cavernous hemangioma

image Common autopsy finding, may be >1% occurrence
image More common in women > 30, but can be found in any age group or sex

• Focal nodular hyperplasia (a.k.a. focal cirrhosis): second most common benign solid tumor
• Hepatic adenoma
image

Tumors, Secondary and Metastatic

image

Primary Hepatic Carcinoma

Malignant Tumors

• Primary lesions
• Hepatocellular carcinoma

image One of the most common malignancies worldwide
image Associated most strongly with chronic viral hepatitis
image Usually occurs with cirrhosis

• Metastatic lesions

image More common than primary tumors in the rest of the world
image Virtually any primary tumor can metastasize to liver.
image Only colorectal and some pancreatic islet carcinomas typically make resectable tumors.
image Carcinoid and leiomyosarcoma tumors can also be resectable.

image

Cirrhosis

Cirrhosis and Liver Failure

• Cirrhosis is most common cause of liver failure.
• Mechanism of cirrhosis: hepatocyte destruction → fibrosis and scarring → venous hypertension → portal venous congestion → lymphatic overload → lymph leakage and ascites
• Prothrombin time is best indicator of synthetic function.
• Hepatic encephalopathy: metabolic deficit leads to buildup of ammonia, methane thiols, mercaptans, and false neurotransmitters
• Increased aldosterone, secondary to impaired metabolism and low glomerular filtration rate
• Peritoneovenous shunts (LeVeen, Denver) used to drain ascites fluid into venous system

Abscesses

• Historically challenging to treat
• Pyogenic (bacterial)

image Predisposing: biliary diseases or infections in areas with portal drainage (appendicitis, diverticulitis, perforating neoplasms)
image Less common causes: bacteremic seeding, trauma, chronic suppurative infections
image Ultrasound and CT offer high diagnostic accuracy.
image Principles of treatment

image Abscess drainage
image Percutaneous with ultrasound or CT
image Approaching effectiveness of open surgical drainage

image 8%-22% mortality in recent series
image Complications: rupture into adjacent structure, dissemination, and multiorgan failure

• Amebic: Entamoeba histolytica

image Emigration from or travel through region with endemic amebic disease
image Ingested cysts break down to form mobile trophozoite.
image Trophozoites inhabit colon or its wall.
image Liver invaded via portal drainage, with necrosis and abscess formation
image Ultrasound may be diagnostic (>90%), with no need for CT.
image Serologic test for E. histolytica antibodies confirms diagnosis.

Hemobilia

• Gastrointestinal hemorrhage secondary to biliary tract bleeding
• Occurs from sites in biliary system, from liver parenchyma through other locations in duct system and gallbladder
• Trauma, infection, or tumor can cause hemorrhage into biliary tree.
• Trauma and iatrogenic injury are common causes in the U.S. (biopsy, stents, ERCP [see Chapter 8, Biliary Diseases]).
• May be massive or minimal, depending on source, etiology

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