Liver anatomy, physiology and diseases affecting liver Tejaswini Arcot Sep 16, 2022 Anatomy • The liver is the second largest (after the skin) organ in the human body and the largest gland (weighing an average of 1500 g). • It lies under the diaphragm in the right upper abdomen and midabdomen and extends to the left upper abdomen. • The liver has the general shape of a prism or wedge, with its base to the right and its apex to the left (see the image below). • It is pinkish brown in color, with a soft consistency, and is highly vascular and easily friable. Liver anatomy Anatomy • The liver is grossly divided into two parts when viewed from above – a right and a left lobe • The falciform ligament makes a superficial division of the liver into a left and right lobe. • In Couinaud system, the functional lobes are further divided into a total of eight subsegments based on a transverse plane through the bifurcation of the main portal vein. Anatomy • The caudate lobe is a separate structure that receives blood flow from both the right- and left-sided vascular branches. • The Couinaud classification divides the liver into eight functionally independent liver segments. • Each segment has its own vascular inflow, outflow and biliary drainage. Physiology • Carbohydrate and protein metabolism • The liver is thought to be responsible for up to 500 separate functions, usually in combination with other systems and organs. Currently, no artificial organ or device is capable of reproducing all the functions of the liver. • The liver stores a multitude of substances, including vitamin A (1–2 years’ supply), vitamin D (1–4 months’ supply), vitamin B12 (3–5 years’ supply), vitamin K, vitamin E, iron, copper, zinc, cobalt, molybdenum, etc. Physiology • Haemopoiesis - The formation of blood cells is called haemopoiesis. In embryonic stage RBC and WBC are formed by liver. In the first trimester fetus, the liver is the main site of red blood cell production. By the 32nd week of gestation, the bone marrow has almost completely taken over that task. • Liver helps in purification of blood. The Kupffer cells of liver are phagocytic cells, helps in phagocytosis of dead blood cells and bacteria from the blood. • The liver is responsible for immunological effects – the mononuclear phagocyte system of the liver contains many immunologically active cells, acting as a ‘sieve’ for antigens carried to it via the portal system. Physiology • The liver produces albumin, the most abundant protein in blood serum. It is essential in the maintenance of oncotic pressure, and acts as a transport for fatty acids and steroid hormones. • The liver synthesizes angiotensinogen, a hormone that is responsible for raising the blood pressure when activated by renin, an enzyme that is released when the kidney senses low blood pressure. • The liver produces the enzyme catalase to break down hydrogen peroxide, a toxic oxidising agent, into water and LFTs • Liver function tests (LFTs or LFs), also referred to as a hepatic panel, are groups of blood tests that provide information about the state of a patient’s liver. • These tests include prothrombin time (PT/INR), activated Partial Thromboplastin Time (aPTT), albumin, bilirubin (direct and indirect), and others. The liver transaminases aspartate transaminase (AST or SGOT) and alanine transaminase (ALT or SGPT) are useful biomarkers of liver injury in a patient with some degree of intact liver function. LFTs • Most liver diseases cause only mild symptoms initially, but these diseases must be detected early. Some tests are associated with functionality (e.g., albumin), some with cellular integrity (e.g., transaminase), and some with conditions linked to the biliary tract (gamma-glutamyl transferase and alkaline phosphatase). Normal range Hydatid cyst • Hydatid cyst is a parasitic disease of tapeworms of the Echinococcus type. The two main types of the disease are cystic echinococcosis and alveolar echinococcosis. • The disease often starts without symptoms and this may last for years. The symptoms and signs that occur depend on the cyst’s location and size. Alveolar disease usually begins in the liver, but can spread to other parts of the body, such as the lungs or brain • The eggs are released in the stool of meat-eating animals that are infected by the parasite. Commonly infected animals include dogs, foxes, and wolves. • The type of disease that occurs in human patients depends on the type of Echinococcus causing the infection. Diagnosis is usually by ultrasound though computer tomography (CT) or magnetic resonance imaging (MRI) may also be used. Blood tests looking for antibodies against the parasite may be helpful as may biopsy. Hydatid cyst • Prevention of cystic disease is by treating dogs that may carry the disease and vaccination of sheep. • Treatment is often difficult. • The cystic disease may be drained through the skin, followed by medication. • Sometimes this type of disease is just watched. • The alveolar form often requires surgical intervention, followed by medications. The medication used is albendazole, which may be needed for years. The alveolar disease may result in death. cyst appearance End stage liver disease • end-stage liver disease, is the impaired liver function caused by the formation of scar tissue known as fibrosis due to damage caused by liver disease. • damage causes tissue repair and subsequent formation of scar tissue, which over time can replace normal functioning tissue, leading to the impaired liver function of cirrhosis. • the disease typically develops slowly over months or years. • early symptoms may include tiredness, weakness, loss of appetite, unexplained weight loss, nausea and vomiting, and discomfort in the right upper quadrant of the abdomen. cirrhosis End stage liver disease • as the disease worsens, symptoms may include itchiness, swelling in the lower legs, fluid build-up in the abdomen, jaundice, bruising easily, and the development of spider-like blood vessels in the skin. • the fluid build-up in the abdomen may become spontaneously infected. • more serious complications include hepatic encephalopathy, bleeding from dilated veins in the esophagus, stomach, or intestines, and liver cancer. End stage liver disease • Cirrhosis is most commonly caused by alcoholic liver disease, non-alcoholic steatohepatitis (NASH – the progressive form of non-alcoholic fatty liver disease), heroin abuse, chronic hepatitis B, and chronic hepatitis C. • Heavy drinking over a number of years can cause alcoholic liver disease. • Liver damage has also been attributed to heroin usage over an extended period of time as well. End stage liver disease • NASH has a number of causes, including obesity, high blood pressure, abnormal levels of cholesterol, type 2 diabetes, and metabolic syndrome. • Less common causes of cirrhosis include autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis that disrupts bile duct function, genetic disorders such as Wilson’s disease and hereditary hemochromatosis, and chronic heart failure with liver congestion. • Diagnosis is based on blood tests, medical imaging, and liver biopsy.
