⁨أسئلة السابعة جراحة حورس ثالثة Liver Anatomy and Structures

Liver Anatomy

• The Liver is the largest organ in the body
• The Liver weighs 1.5 kg in the average 70-kg man
• Liver parenchyma has a thin capsule and a visceral peritoneum covering except for the posterior surface where it is known as the "bare area"
• The right lobe is large, about ¾ of the liver parenchyma, while the left lobe is smaller
• The liver gets blood from the portal vein (80%) and from the hepatic artery (20%)
• Arterial blood comes from the coeliac trunk of the aorta, where the hepatic artery arises along with the splenic artery
• Hepatic veins drain into the IVC
• Major venous drainage occurs through three large veins joining the IVC immediately below the diaphragm

Structures in the Hilum

• Porta Hepatis refers to a transverse fissure on the visceral surface of the liver
• The hepatic artery, portal vein, and bile duct are present within the free edge of the lesser omentum or hepatoduodenal ligament, which, along with nerves and lymphatics, enters the liver at the porta hepatis
• Anatomical relationship: bile duct within the free edge, hepatic artery above and medial, and portal vein posteriorly
• The common hepatic duct joins the cystic duct within this ligament to form the common bile duct
• The common hepatic artery branches at a variable level in the ligament, forming two or three main arterial branches
• The right hepatic artery crosses the bile duct either anteriorly or posteriorly before giving rise to the cystic artery and multiple small hepatic arterial branches provide blood to the bile duct, mainly from the right hepatic artery
• The portal vein arises from the confluence of the splenic vein and the superior mesenteric vein behind the neck of the pancreas.
• It has important tributaries, including the left gastric vein, which joins just above the pancreas

Division of Structures

• At the hilum, the major structures branch into right and left divisions.
• The right and left hepatic ducts arise from the hepatic parenchyma and join to form the common hepatic duct
• The left duct has a longer extrahepatic course of ~2 cm
• Fibrous sheaths surround ducts accompanying branches of the hepatic artery and portal vein within liver parenchyma
• The portal vein often gives off two large branches outside the liver before a left branch runs behind the left hepatic duct

Segmental Anatomy

• The liver is divided into eight segments.
• Each segment is a functional unit with a branch of hepatic artery, portal vein, and bile duct being drained by the hepatic vein
• The liver's overall anatomy is divided into functional right and left 'units' along a line between the gallbladder fossa and the middle hepatic vein (Cantlie’s line)
• Liver segments V-VIII are located to the right of this line.
  • They are supplied by the right hepatic artery and the right branch of the portal vein
  • Bile is drained through the right hepatic duct
• Segments I-IV exist to the left of this line and are functionally the left liver.
  • They are supplied by the left branch of the hepatic artery and the left portal vein branch

The Hepatic Lobules

• Functional units existing in liver segments
• These comprise plates of liver cells separated by the hepatic sinusoids, which are large, thin-walled venous channels that carry blood to the central vein, a tributary of the hepatic vein, from the portal tracts containing branches of hepatic artery and portal vein
• During its passage, many liver functions occur in the sinusoids, including bile formation, which is channeled in the opposite direction to the blood flow to drain through duct tributaries within the portal tracts that drains into the left hepatic duct

Hepatectomy Procedures

• Right Hepatectomy: Segments V, VI, VII, and VIII (± segment I)
• Left Hepatectomy: Segments II, III, and IV (± segment I)
• Right Posterior Sectionectomy: Segments VI and VII
• Right Anterior Sectionectomy: Segments V and VIII
• Left Medial Sectionectomy: Segment IV
• Left Lateral Sectionectomy: Segments II and III
• Extended Right/Right Trisegmentectomy: Segments IV, V, VI, VII, and VIII (± segment I)
• Extended Left/Left Trisegmentectomy: Segments II, III, IV, V and VIII (± segment I)

Indications for Liver Resection

• Benign tumors
• Malignant tumors
• Trauma
• Others

Infections of the Liver

• Viral hepatitis
• Pyogenic liver abscess
• Amoebic Hepatitis and abscess
• Hydatid disease of the liver
• Hepatic Schistosomiasis

Pyogenic Liver Abscess

• A serious and highly fatal disease improved with early diagnosis
• Modern radiology, diagnostics, interventional radiology, and antibiotics have led to safer management

Etiology of Pyogenic Liver Abscesses

• Biliary tract (cholangitic abscess):

  • It is the most common of all sources
  • Ascending cholangitis caused by bile duct obstruction results in multiple liver abscesses involving E. coli or other gram-negative bacilli

• Portal vein:

  • Suppurative appendicitis or colon diverticulitis may induce septic thrombophlebitis of the portal vein radicles, with consequent portal pyaemia and multiple liver abscesses
  • Common organisms are streptococci and anaerobes, but fewer patients present because of early use of potent antibiotics

• Arterial system (haematogenous abscess):

  • Bacterial endocarditis, tonsillitis, intravenous drug misuse, or osteomyelitis can act as sources
  • Staphylococcus aureus is a usual causative organism

• Idiopathic:

  • The source of infection cannot be traced

Predisposing Factors for Pyogenic Liver Abscess

• Immuno-compromised patients
  • Individuals with diabetes mellitus, leukemia, chronic illness, those who are elderly or alcoholic, and transplant recipients receiving immunosuppressive therapy
• Already existing liver lesion if a hydatid cyst, amoebic abscess, or hematoma gets secondarily infected

Complications of Pyogenic Liver Abscess

• Direct extension of abscess may involve the pleura, lung, pericardium, or peritoneum

Clinical Features of Pyogenic Liver Abscess

• Fever and its constitutional manifestations, toxaemia, together with right hypochondrial or lower chest pain
• Abdominal examination may reveal a tender hepatomegaly, which may be absent, with the patient presenting with a pyrexia of unknown origin

Investigations for Pyogenic Liver Abscess

• Laboratory:

  • Leukocytosis
  • Anemia and high ESR
  • Low serum albumin
  • High alkaline phosphatase and transaminases level
  • Elevated serum bilirubin occurs in cases of cholangitis or with multiple abscesses

• Imaging:

  • An US or CT scan accurately diagnoses and localizes the abscess

Treatment for Pyogenic Liver Abscess

• Broad-spectrum antibiotics
  • "The treatment for any abscess is drainage of pus.”
• Percutaneous guided drainage of pus:
  • Simple procedure under local anesthesia with US or CT guidance to direct needle to abscess cavity, then aspiration and a tube drain insertion.
  • This has replaced the standard method of open surgical drainage.

Amoebic Hepatitis and Abscess

• Commonly occurs in developing countries, particularly those in tropical and subtropical regions
• Low hygiene standards and high humidity favor amoebiasis infestation

Pathology of Amoebic Hepatitis and Abscess

• Etiology: Entamoeba histolytica is endemic worldwide and spreads by the faeco-oral route in vegetative form
• Amoebic cysts are ingested and develop into the trophozoite form in the colon, then pass through the bowel wall to liver via the portal blood

Clinical Presentation of Amoebic Hepatitis and Abscess

• Dysentery is the most familiar presentation
• It may present as an amoebic abscess, more frequently in the liver and paracaecal regions
• Investigations:
  • Positive stool analysis and serological tests are useful in non-endemic areas
  • Blood picture: reveals leukocytosis and anemia
  • Imaging is critical for diagnosis, similar to pyogenic abscess
  • Ultrasound or CT scanning can detect the number, site, and size of abscesses
  • Chest X-ray detects pleural effusion and pulmonary collapse and reveals an elevated right' cupola of the diaphragm
• Therapeutic test: improvement in local and general conditions after the therapeutic use of metronidazole treatment confirms the diagnosis

Treatment for Amoebic Hepatitis and Abscess

• Conservative Treatment:
  • Metronidazole is the drug of choice in an 800mg dose three times daily for 7-10 days
• Ultrasound-guided percutaneous aspiration is performed for abscesses that fail to respond in 72 hours and for large abscesses
  • A large-bore spinal needle is used with local anesthesia and site aspiration relative to site of abscess
  • Anterior insertion: needle introduced below costal margin anteriorly
  • Posterior insertion: needle is inserted in the 10th intercostal space posteriorly.
  • Ultrasound is repeated several days after and aspiration is repeated if cavity refilled and is greater than 5cm.
• Open Drainage:
  • Indications: secondary infection, a pointing abscess, difficult aspiration when caused by a multilocular abscess or thick pus
  • An extrapleural approach is taken through the bed of the 12th rib posteriorly since amoebic abscesses are in the postero-superior segment of the right lobe

Hydatid Disease of the Liver

• The disease is prevalent in sheep-rearing parts of the world and is commonly seen in Iraq, Yemen, and Libya, as well as Egypt
• Etiology: Tapeworm Echinococcus granulosus

Life Cycle of Hydatid Disease

• Adult worms live in the intestine of the dog, which is the definitive host and pass ova in their stool
• Sheep may ingest the ova as they feed on contaminated grass.
• The ova hatch in the sheep’s stomach, penetrate the wall, and enter the portal venous system to lodge and form cysts mostly in the liver and, less frequently, in the lungs or brain
• Sheep are the secondary host.
• Humans may become accidental secondary hosts via vegetables or hands contaminated with dog excreta
• Parasites continue its life cycle when dogs feed on offal of dead sheep

Pathology of Hydatid Disease

• The liver may be impacted by a single or multiple hydatid cysts
• Cyst fluid is usually colorless and clear but may be yellowish if the cyst connects to the bile ducts
• Scolices, if found in cyst fluid, can cause a severe anaphylactic reaction if they get to circulation

Microscopic Picture of Hydatid Disease

• The double-layered cyst wall is formed by: Inner thin layer (endocyst), formed by the inner germinal layer, and the outer laminated membrane
• The endocyst shows folds with brood capsules containing the heads of future worms (scolices)
• This is the living parasite part secreting the hydatid fluid
• The host surrounds the parasite with a third, outermost adventitial fibrous tissue layer as a reaction
• Daughter cysts may develop inside the main cyst

Fate and Complications of Hydatid Disease

• The Variable Fate is variable
  • The majority of cysts enlarge gradually or calcify once the parasite dies
• Smaller proportions present life-endangering complications, such as:
  • Secondary bacterial infection
  • Cyst rupture in biliary passages, causing jaundice
  • Rupture in peritoneal cavity, causing dissemination and anaphylactic reaction

Clinical Features of Hydatid Disease

• Cysts that are asymptomatic for years being discovered by ultrasonography used for another purpose
• Typical Presentation: Chronic right upper quadrant ache and hepatomegaly
• The disease may present with one of its complications

Investigations for Hydatid Disease

• Ultrasound: multiloculated cyst on ultrasound
• CT: floating membrane within the cysts
• Serology for antibodies to hydatid antigen can be done with use of the enzyme-linked immunosorbent assay (ELISA)

Treatment for Hydatid Disease

• Indications are to prevent progressive enlargement and rupture of cysts
• Albendazole or mebendazole pre and postoperatively
• Surgical options:
  • Evacuate contents with aspiration, close the system, and disinfect with 20% saline
  • Deroot and excise the endocyst, liver resection, or local cyst section
  • Avoid peritoneal contamination during surgery with active hydatid daughters by continuous medication of Albendazole or Praziquantel
  • Pack peritoneal cavity with 20% hypertonic saline-soaked packs and instill 20% into cyst, actively seek and suture any biliary connection
• Endoscopic:
  • Remove daughter cysts from the biliary tree if with obstructive jaundice
• PAIR
  • Puncture of the cyst under image guidance
  • Aspiration of the cysts content
  • Instillation of hypertonic solution into the cyst cavity
  • Re-Aspiration

Liver Cell Adenoma

• Considered a true benign neoplasm of hepatocytes
• Occurs almost exclusively in women
• Etiology: is promoted by contraceptive pills and tumor regression occurs if intake is stopped Pathology:
  • Soft well-circumscribed in gross appearance and are light yellow with multiple cases occurring in ⅓ of cases
  • Histologically: the neoplasm has sheets of regular hepatocytes displaying thin-walled vessels yet no portal triads

Clinical Presentation of Liver Cell Adenoma

• Asymptomatic and discovered incidentally at ultrasound examinations or at laparotomy
• Sometimes, a large LCA causes right upper quadrant pain

Complications and Investigations for Liver Cell Adenoma

• Complications: malignant transformations and spontaneous rupture that causes internal hemorrhage
• Investigations: Imaging via US, CT, and/or MRI; liver function tests and α-fetoprotein are normal

Treatment for Liver Cell Adenoma

• Involves liver resection since it can develop malignancy and for large, symptomatic tumors

Haemangioma

• The commonest benign tumor of the liver
• Cavity types may be large
• Usually harmless, though occasional rupture can lead to serious bleeding

Presentation and Investigations for Haemangioma

• Clinical silent or abdominal pain or Other atypical presentation
• Investigations: Laboratory with CBC, liver functions, α-fetoprotein
• Radiological:
  • Ultrasound
  • Delayed contrast enhancement on CT indicating slow vessel uptake in the hemangioma
  • MRI
• Biopsy is contraindicated

Treatment for Haemangioma

• Management via patient reassurance and observation during discovery
• Giant symptomatic: enucleation vs resection

Focal Nodular Hyperplasia

• An unusual benign condition of unknown etiology where there is a focal overgrowth of functioning liver tissue supported by fibrous stroma
• Commonly impacts patients in middle-age who are female and has no association with underlying Liver Disease. The FNH consists of both hepatocytes and Kupffer cells

Diagnostic Characteristics of Focal Nodular Hyperplasia

• Ultrasound: showing a solid tumor mass
• Contrast-enhanced CT or/and MRI: presents a center showcasing scarring and evidence of high vascularized lesion - may not show specificity for focal nodular hyperplasia FNH
• MRI: is highly valued
• Sulphur colloid liver scan can be useful

Treatment for Focal Nodular Hyperplasia

• No malignant potential, and they do not require any treatment after the condition is confirmed