Liver


Segmental classification of the liver. (With permission from Mulholland MW, Lillemoe KD, Doherty GM, Maier RV, Upchurch GR, eds. Greenfield’s Surgery. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.)


Lobar Classification


Liver is divided into the right and left lobes


Lobes are separated by Cantlie line, which runs from the gallbladder fossa to the inferior vena cava (IVC)


The caudate lobe is distinct from the right and left lobes because its venous drainage is directly into the IVC



Lobar classification of the liver. (With permission from Mulholland MW, Lillemoe KD, Doherty GM, Maier RV, Upchurch GR, eds. Greenfield’s Surgery. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.)


Other Perihepatic Structures


Falciform ligament


Separates the medial and lateral segments of the left lobe


Attaches the liver to the abdominal wall


Ligamentum teres


Carries the obliterated umbilical vein


Triangular ligaments


Lateral and medial extensions of the coronary ligaments on the posterior surface of the liver


Made of peritoneum



Perihepatic ligaments. (With permission from Fischer JE, Bland KI, Callery MP, et al., eds. Mastery of Surgery. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.)


Hepatoduodenal ligament


Where the bile duct, portal vein, and hepatic artery meet (the portal triad)


Foramen of Winslow


Anterior—portal triad


Posterior—IVC


Inferior—duodenum


Superior—liver


What cells in the liver are most susceptible to ischemic insult and what cells are most susceptible to toxic or chemical injury?


The hepatocytes are the most susceptible to ischemic injury, and the biliary ductule is the most susceptible to toxic or chemical injury.


Microscopic Anatomy of the Liver


Acinar unit


The functional unit of the liver


Includes the biliary ductule, the hepatic arteriole, and the portal venule


Zones are defined relative to oxygen and solute concentration gradients


Zone 1


Closest to portal triad


Most susceptible to toxic injury, least susceptible to ischemia


Zone 3


Contains hepatocytes


Adjacent to the terminal hepatic vein


Most susceptible to ischemic injury


Alkaline phosphatase is in the canalicular system


Nutrient uptake occurs in the sinusoidal membrane


During a routine cholecystectomy, the gallbladder is very inflamed and due to poor visualization, the common hepatic artery is mistaken for the cystic artery and is ligated. What will be the remaining blood flow and oxygen supply to the liver?


The liver will still have 75% of its original blood flow, but only 50% of its original oxygen delivery.


Blood Supply of the Liver


Portal vein


Supplies 75% of the blood flow to the liver and 50% of the oxygen supply


Formed by the superior mesenteric vein (SMV) and splenic veins


Inferior mesenteric vein drains into the splenic veins (or occasionally, into the SMV)


Hepatic artery


Supplies 25% of the blood flow to the liver and 50% of the oxygen supply


Becomes the proper hepatic artery after the gastroduodenal artery branches off, and then branches into the right and left hepatic arteries


Approximately 10% of patients will have



Periportal anatomy. (With permission from Mulholland MW, Lillemoe KD, Doherty GM, Maier RV, Upchurch GR, eds. Greenfield’s Surgery. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.)


A replaced/accessory right hepatic artery arising from the superior mesenteric artery that travels posterolateral to the common bile duct (CBD) in the porta hepatis


A replaced/accessory left hepatic artery arising from the left gastric artery that travels through the gastrohepatic ligament into the falciform ligament


Hepatic vein (HV)


3 venous branches


Left HV: Drains segments II, III, and IVA


Right HV: Drains segments VI, VII, and VIII


Middle HV: Drains segments IV and V


Caudate lobe (segment I) drains directly into the IVC


What is the lymphatic drainage of the liver?


Lymphatic Drainage of the Liver


Lymphatic drainage starts in perisinusoidal spaces of Disse and clefts of Mall


These drain into the porta hepatis


Porta hepatis drains to cisterna chili


Cisterna chili drains into thoracic duct


Lymphatics are on the right side of the CBD


Pathophysiology of ascites


Decreased permeability of sinusoidal epithelial cells altered lymphatic drainage ascites


In addition to bile production and hemoglobin degradation, what are the physiologic functions of the liver?


The liver also does detoxification, nutrient storage, glucose, lipid and protein metabolism, and protein synthesis.


Detoxification


Cytochrome P450 system


Conversion of hydrophobic to hydrophilic compounds to improve solubility for secretion


Reactions include reduction, hydroxylation, and hydrolysis to expose functional groups


Phase II reactions


Conjugation to alter solubility


Nutrient Storage


Glycogen


Triglycerides


Vitamin B12


Copper


Fat-soluble vitamins


Protein Synthesis


Coagulation factors: I, II, V, VII, IX, X, and XI, antithrombin III, protein C/S


Factor VIII is made primarily by endothelial cells, but a small proportion is made in the liver


Complement factors


Acute phase proteins: Transferrin, CRP, fibrinogen, haptoglobin, albumin, ceruloplasmin


Protein, Lipid, and Glucose Metabolisms


Glycogenesis and glycogenolysis + gluconeogenesis, depending on the body’s state of metabolism


Lipogenesis (from amino acids and glucose)


Deamination and transamination of amino acids


Urea cycle—conversion of ammonia to urea


Production of non-essential amino acids


A 63-year-old woman with a history of unresectable bile duct cancer (cholangiocarcinoma) status post biliary stenting presents with a 1-week history of fevers, chills, and jaundice. An abdominal CT reveals multiple rim-enhancing fluid collections in the liver. What is the most likely diagnosis?


A hepatic abscess usually presents following episodes of intra-abdominal infection or bacteremia and is characterized by a rim-enhancing fluid collection on CT scan. Common organisms include Escherichia coli, Klebsiella, Proteus, Staphylococcus, and Streptococcus. Fungus may be found in immunocompromised patients or in patients with multi-organism hepatobiliary infection. Amebic abscesses are caused by Entamoeba histolytica.



Pyogenic liver abscess. (With permission from Fischer JE, Bland KI, Callery MP, et al., eds. Mastery of Surgery. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.)


Pyogenic Liver Abscess


Causes


Biliary instrumentation (most common)


Biliary obstruction from stones, strictures, and tumors


Portal vein spread of gastrointestinal infections such as diverticulitis, appendicitis, or perforated ulcers


Hematogenous spread via hepatic artery in the setting of systemic bacteremia


Unknown etiology in up to 20% of patients


Diagnosis


Most common type of liver abscess in the United States


Patients present with fever, chills, and right upper quadrant abdominal pain


Jaundice, weight loss, nausea, and vomiting can also be seen


Up to one-quarter of patients will be septic


Lab tests show leukocytosis, elevated bilirubin, and alkaline phosphatase


Plain abdominal films or abdominal CT may show gas in the abscess cavity and elevation of the right hemidiaphragm


CT can also demonstrate contrast-enhancing, well-defined round masses with low internal density


Ultrasound demonstrates hypoechoic lesions


Treatment


Percutaneous drainage is the treatment of choice


Laparoscopic or open surgical drainage is used when percutaneous drainage is not possible or the source of infection is surgically correctable


Microabscesses in patients in good condition can be treated with antibiotics alone


Broad-spectrum antibiotics should be substituted with culture-guided antibiotics as soon as the organisms are identified



Causes of pyogenic liver abscess. (With permission from Fischer JE, Bland KI, Callery MP, et al., eds. Mastery of Surgery. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.)


When choosing a method of drainage, factors that should be considered include the anesthetic risk and underlying clinical condition of the patient, as well as the local expertise in and availability of each drainage method.


Amebic Liver Abscess


Most common cause of liver abscess worldwide


Complication of intestinal amebiasis (E. histolytica) in 3% to 10% of cases; spreads to the liver via the portal vein


Symptoms/history


History of travel to a tropical climate


Fever


Abdominal pain and hepatomegaly


Diarrhea is present in only 20% to 30% of the cases


Often patients do NOT have jaundice


The abscess can rupture into pleura, pericardium, or peritoneum


Diagnosis


Often a solitary lesion in the right lobe of the liver


CT scan shows low internal density and smooth margins


Serology (indirect hemagglutination and gel diffusion precipitation) is the most accurate test for diagnosis


Stool testing for the cyst of the protozoan is negative in most cases


Treatment


Metronidazole is effective in most cases


Aspiration may be required for larger abscesses


Surgical drainage is reserved for patients with secondary infection, perforation with peritoneal irritation, or failure of metronidazole therapy


History of travel to a tropical area in a young patient with a solitary liver cavity should prompt serology investigation for an amebic abscess.


A 38-year-old man who recently emigrated from Sudan presents to the emergency department with nausea, vomiting, and jaundice. A CT scan reveals a large, solitary, calcified cyst in the right lobe of the liver. Serologic tests confirm infection with Echinococcus. What is the next step in the management of this cyst?


The cyst should be excised completely, including sterilization of the cyst and excision of the germinal layer.



Echinococcal cyst. (With permission from Mulholland MW, Lillemoe KD, Doherty GM, Maier RV, Upchurch GR, eds. Greenfield’s Surgery. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.)


Echinococcal Cyst


Caused by the larval stage of the tapeworm Echinococcus


Infection occurs through ingestion of parasite eggs


Eggs are released in the feces of the definitive host (carnivores and rodents)


Eggs hatch and migrate across the intestinal wall of the intermediate host, spreading to the liver (most commonly), brain, lungs, and bones


Patients are often from endemic areas such as the Mediterranean and Baltic areas, Middle and Far East, South America and South Africa


There is an asymptomatic phase of variable duration


Clinical manifestations include fever, abdominal pain, jaundice, and weight loss


Serology (indirect hemagglutination) has good sensitivity


Can also have a positive Casoni skin test (intradermal injection of sterilized fluid from hydatid cysts that results in wheal response; high false positive rate limits its utility)


Imaging with ultrasound or CT scan usually shows a unilocular or complex lesion with daughter cysts


Thick calcified rims are seen in dead cysts


Rupture, most commonly to the

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Apr 20, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Liver
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