Gastrointestinal and liver disorders

Most of the gastrointestinal tract is packed in the abdomen like convoluted plumbing. For clarity, it has been separated and extended in the diagram (below right).

In present-day Western society, smoking, diet, and the consumption of alcohol are the commonest direct or indirect causes of most disorders of the gastrointestinal tract and the liver. Almost all gastrointestinal infections are acquired in this way, as are some forms of hepatitis.

The esophagus, stomach, and duodenum

Many disorders of the upper gastrointestinal tract are caused by acids produced by the stomach in abnormal amounts or locations. These disorders often share a common symptom: a burning pain in the lower chest (heartburn).

Duodenal ulcers are thought to be at least partly caused by excess acid. Many people with ulcers are also infected with Helicobacter pylori, a bacterium that lives in the stomach. H. pylori may increase stomach acid production, or it may produce a toxin that damages the stomach lining. Ulcers may require surgery, especially if erosion reaches an artery and causes hemorrhage.
Virus infections and the bacterial contamination of food cause inflammation of the stomach and small intestine (gastritis). Symptoms include vomiting and diarrhea, both of which are urgent attempts by the body to expel the noxious agent. Serious bacterial infections include cholera, typhoid, and some forms of dysentery, which are treated with antibiotics. Dehydration due to fluid loss and non absorption of fluids by the inflamed intestines must also be treated, sometimes by an intravenous saline drip. Drugs which the gastrointestinal tract may not be able to absorb in these diseases—are sometimes administered intravenously too.

Celiac disease is an abnormal reaction to the protein gluten, present in wheat; individuals affected have to follow a strict diet avoiding all wheat and wheat-flour products.

Hepatitis B, which results in inflammation of the liver and symptoms of jaundice, is caused by a virus, shown here in a false-color electron micrograph. It is highly infectious and is spread by various means, including contaminated hypodermic needles and saliva.

Intestinal disorders

Disorders affecting the intestines usually cause either diarrhea, constipation, or failure to absorb nutrients such as vitamins and iron, although a low-fiber diet (such as one low in fresh vegetables) may also be a cause of constipation.

Appendicitis occurs when inflammation develops in the wormlike appendix. Treatment is by surgical removal of the appendix, which is usually necessary to prevent it from bursting and so contaminating the membrane that lines the abdominal cavity and other abdominal organs.
Crohn’s disease and ulcerative colitis are conditions in which parts of the bowel become inflamed and ulcerated. The cause is unknown. Symptoms such as cramping pain and severe diarrhea are treated with drugs, but occasionally surgery is necessary. Irritable bowel syndrome (spastic colon) produces the same symptoms without organic disease.

Hemorrhoids (piles) are dilated veins in the wall of the rectum and anal canal. These may descend through the anus and become trapped there. They are strongly associated with constipation. If the disorder becomes persistent, thrombosing the dilated vein (blocking it, entirely sealing it off) by injection may relieve the symptoms. Surgery may be required. Cancer of the lower bowel (colon and rectum) is common, but can be cured if the growth is removed in its early stages. In some cases, this treatment requires an artificial opening (colostomy) to be made from the colon through the abdominal wall. It is essential that people with a family history of bowel cancer be screened regularly, beginning at an early age. Others should be screened starting at age 50.

The whole digestive tract (right) from esophagus to rectum is susceptible to various disorders, particularly inflammation, resulting in such disorders as gastritis, appendicitis, and colitis. Ulceration and tumors are more serious conditions that can affect the tract.

The pancreas and gall bladder

These organs produce and store digestive enzymes and bile required for the digestion of fats. The commonest disorder of the pancreas affects the endocrine cells secreting insulin and glucagon, and causes a type of diabetes that is treated as a specialized glandular disorder. Abnormalities in the bile result in gallstones, which in turn may cause inflammation of the gall bladder. The symptoms (abdominal pain and flatulence) are worse after fatty meals. If gallstones block the flow of pancreatic secretions, the pancreas may become inflamed, causing pancreatitis. This can also occur as a result of alcohol abuse. If cancer affects the pancreas, it is usually fatal.

Endoscopy allows a physician to observe directly internal parts of the body—in this illustration an ulcer in the stomach—without cutting through external layers. In some cases, endoscopic surgery can also be performed or tissue samples taken using minute instruments attached to the head of the endoscope.

Liver disorders

The liver converts nutrients absorbed from the gastrointestinal tract into products the tissues can use and excretes breakdown products in bile. Any disorder interfering with bile production or excretion may cause jaundice.

At least three major types of viral hepatitis are known. Hepatitis A virus is contracted through contaminated water or food, and the disease is normally self-limiting. Hepatitis B virus and non-A/non-B virus are transmitted in blood or body fluids; they present a small risk of rapid and fatal liver failure, and also a slightly greater risk of persistent infection, which may lead to liver degeneration over several years. Hepatitis may result from alcohol abuse or, rarely, is a complication of drug treatment. Vaccines against hepatitis B virus are also becoming available. Protection against hepatitis B virus, which is particularly common in the tropics, can be achieved by injections of immune globulin, although the effect is only temporary.

Cirrhosis of the liver in which nodules form on areas of the liver already affected by fibrosis is generally progressive and results in eventual death, unless the cause can be eliminated. A major cause is alcoholism; others are chronic viral hepatitis and some autoimmune disorders.

Liver cancer is rare in Europe, except in patients with cirrhosis, but is very common in countries where many people suffer chronic hepatitis B infection. The close link between the virus and liver cancer makes possible the prevention of the latter by immunization against hepatitis B.