The silent dragon—hepatitis C - Home Study Program

AORN Journal, June, 2003 by Beverly Walker, Linda Howard

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Cellular structure. The liver's cellular structure is a plate-like arrangement of hepatocytes (ie, parenchymal liver cells that perform all liver functions) one to two cells thick. They are separated by large capillary spaces called sinusoids. This arrangement and the permeability of the sinusoids allow intimate contact between blood and hepatocytes. The hepatic plates are arranged further into functional units called lobules. In the center of each lobule is a vein, and at its periphery are branches of the portal vein and hepatic artery. (13)

Vasculature. The portal vein drains from the gastrointestinal (GI) tract directly into the liver. Nutrient-rich blood from the GI tract provides 75% of the liver's blood supply. The other 25% is supplied by the hepatic artery. The portal circulation mixes with arterial blood as it moves from the periphery of the lobule to the central vein. The veins merge to carry blood to the inferior vena cava. Hepatocytes also make bile, which is secreted into bile canaliculi (ie, thin channels located in each hepatic plate). The intrahepatic bile passages converge and anastomose, leading into the hepatic duct, which is the excretory channel of the liver. In a healthy liver, blood and bile travel in opposite directions and never meet. (14)

Physiology. The liver performs many vital functions and acts as a homeostatic mechanism within the body. It processes absorbed nutrients from the small intestine, extracting glucose from the bloodstream and converting it to glycogen. The liver extracts excess lipids from the bloodstream and stores them or packages them with proteins to be sent to other parts of the body. The liver releases fats and sugars back into circulation when levels are low or energy demands are made on the body. It also produces clotting factors, albumin, and many other proteins, the balance of which is vital to health and survival, and releases them directly into the bloodstream. (15)

The liver is involved in the metabolism and breakdown of many hormones (eg, estrogen, testosterone, aldosterone, thyroid hormones) and vitamin D. These hormones have far-reaching effects on many system functions; thus, liver disease can cause disturbances in normal sexual function (eg, decreased libido), anatomy (eg, gynecomastia in males), and fluid regulation (eg, dependent edema, ascites). The metabolism of alcohol and many medications entering the body can overwhelm a healthy liver if the doses are large enough. This can cause a nonviral form of hepatitis to occur, resulting in liver damage. (16)

NATURAL PROGRESSION OF THE DISEASE

Infection with HCV, causing end-stage liver disease or liver cancer, can lead to permanent liver damage, cirrhosis, and even death. It takes about 10 years for the liver to develop chronic hepatitis, (17) although within an average of 50 days all patients infected with the virus develop liver cell injury. This is evidenced by elevated serum alanine aminotransferase (ALT) levels. (18) After initial infection, only 25% to 35% of patients develop clinically noticeable symptoms. Antibodies to HCV are detectable, however, in 50% to 70% of people within weeks of onset of infection and in 90% of people after three months. Virtually all patients infected with HCV demonstrate circulating viral RNA in their blood. Some may develop nonspecific symptoms such as mild fatigue or malaise, but most patients first notice symptoms when their liver disease is in advanced stages. (19)