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10.7: Disorders of the Gastrointestinal Tract

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    Crohn’s Rash

    If you had a skin rash like the one in Figure \(\PageIndex{1}\), you probably wouldn’t assume that it was caused by a digestive system disease. However, that’s exactly why the individual in the picture has a rash. He has a gastrointestinal (GI) tract disorder called Crohn’s disease. This disease is one of a group of GI tract disorders that are known collectively as inflammatory bowel disease. Unlike other inflammatory bowel diseases, signs and symptoms of Crohn’s disease may not be confined to the GI tract.

    Crohn's rash
    Figure \(\PageIndex{1}\): Pustules and crusts around the elbows in a patient with Crohn's disease and bowel-associated dermatosis-arthritis syndrome (BADAS).

    Inflammatory Bowel Disease

    Inflammatory bowel disease is a collection of inflammatory conditions primarily affecting the intestines. The two principal inflammatory bowel diseases are Crohn’s disease and ulcerative colitis. Unlike Crohn’s disease, which may affect any part of the GI tract and the joints as well as the skin, ulcerative colitis mainly affects just the colon and rectum. Both diseases occur when the body’s own immune system attacks the digestive system. Both diseases also typically first appear in the late teens or early twenties and occur equally in all sexes and genders.

    Crohn’s Disease

    Crohn’s disease is a type of inflammatory bowel disease that may affect any part of the GI tract from the mouth to the anus, among other body tissues. The most commonly affected region is the ileum, which is the final part of the small intestine. Signs and symptoms of Crohn’s disease typically include abdominal pain, diarrhea (with or without blood), fever, and weight loss. Malnutrition because of faulty absorption of nutrients may also occur. Potential complications of Crohn’s disease include obstructions and abscesses of the bowel. People with Crohn’s disease are also at a slightly greater risk than the general population of developing bowel cancer. Although there is a slight reduction in life expectancy in people with Crohn’s disease, if the disease is well managed, affected people can live full and productive lives.

    Crohn’s disease is caused by a combination of genetic and environmental factors that lead to impairment of the generalized immune response (called innate immunity). The chronic inflammation of Crohn’s disease is thought to be the result of the immune system “trying” to compensate for the impairment. Dozens of genes are likely to be involved, only a few of which have been identified. Because of the genetic component, close relatives such as siblings of people with Crohn’s disease are many times more likely to develop the disease than people in the general population. Environmental factors that appear to increase the risk of the disease include smoking tobacco and eating a diet high in animal proteins. Crohn’s disease is typically diagnosed on the basis of a colonoscopy, which provides a direct visual examination of the inside of the colon and the ileum of the small intestine.

    People with Crohn’s disease typically experience recurring periods of flare-ups followed by remission. There are no medications or surgical procedures that can cure Crohn’s disease, although medications such as anti-inflammatory or immune-suppressing drugs may alleviate symptoms during flare-ups and help maintain remission. Lifestyle changes, such as dietary modifications and smoking cessation, may also help control symptoms and reduce the likelihood of flare-ups. Surgery may be needed to resolve bowel obstructions, abscesses, or other complications of the disease.

    Ulcerative Colitis

    Ulcerative colitis is an inflammatory bowel disease that causes inflammation and ulcers (sores) in the colon and rectum. Unlike Crohn’s disease, other parts of the GI tract are rarely affected in ulcerative colitis. The primary symptoms of the disease are lower abdominal pain and bloody diarrhea. Weight loss, fever, and anemia may also be present. Symptoms typically occur intermittently with periods of no symptoms between flare-ups. People with ulcerative colitis have a considerably increased risk of colon cancer and should be screened for colon cancer more frequently than the general population. However, ulcerative colitis seems to reduce primarily the quality of life and not the lifespan.

    The exact cause of ulcerative colitis is not known. Theories about its cause involve immune system dysfunction, genetics, changes in normal gut bacteria, and lifestyle factors such as a diet high in animal protein and the consumption of alcoholic beverages. Genetic involvement is suspected in part because ulcerative colitis tends to “run” in families. It is likely that multiple genes are involved. Diagnosis is typically made on the basis of colonoscopy and tissue biopsies.

    Lifestyle changes, such as reducing the consumption of animal protein and alcohol, may improve symptoms of ulcerative colitis. A number of medications are also available to treat symptoms and help prolong remission. These include anti-inflammatory drugs and drugs that suppress the immune system. In cases of severe disease, removal of the colon and rectum may be required and can cure the disease.


    Diverticulitis is a digestive disease in which tiny pouches in the wall of the large intestine become infected and inflamed. Symptoms typically include lower abdominal pain of sudden onset. There may also be fever, nausea, diarrhea or constipation, and blood in the stool. Having large intestine pouches called diverticula (Figure \(\PageIndex{2}\)) that are not inflamed is called diverticulosis. Diverticulosis is thought to be due to a combination of genetic and environmental factors and is more common in people who are obese. Infection and inflammation of the pouches (diverticulitis) occur in about 10 to 25 percent of people with diverticulosis and is more common at older ages. The infection is generally caused by bacteria.

    Diverticula, sigmoid colon
    Figure \(\PageIndex{2}\): Multiple pouches called diverticula in the wall of the large intestine

    Diverticulitis can usually be diagnosed with a CT scan. Mild diverticulitis may be treated with oral antibiotics and a short-term liquid diet. For severe cases, intravenous antibiotics, hospitalization, and complete bowel rest (no nourishment via the mouth) may be recommended. Complications such as abscess formation or perforation of the colon require surgery.

    Peptic Ulcer

    A peptic ulcer is a sore in the lining of the stomach or the duodenum (the first part of the small intestine). If the ulcer occurs in the stomach, it is called a gastric ulcer; if it occurs in the duodenum, it is called a duodenal ulcer. The most common symptoms of peptic ulcers are upper abdominal pain that often occurs at night and improves with eating. Other symptoms may include belching, vomiting, weight loss, and poor appetite. However, many people with peptic ulcers, particularly older people, have no symptoms. Peptic ulcers are relatively common, with about 10 percent of people developing a peptic ulcer at some point in their life.

    The most common cause of peptic ulcers is infection with the bacterium Helicobacter pylori, which may be transmitted by food, contaminated water, or human saliva (for example, by kissing or sharing eating utensils). Surprisingly, the bacterial cause of peptic ulcers was not discovered until the 1980s. The scientists who made the discovery are Australians Robin Warren and Barry J. Marshall. Although the two scientists eventually won a Nobel Prize for their discovery, their hypothesis was poorly received at first. To demonstrate the validity of their discovery, Marshall used himself in an experiment. He drank a culture of bacteria from a peptic ulcer patient and developed symptoms of peptic ulcer in a matter of days. His symptoms resolved on their own within a couple of weeks, but he took antibiotics to kill any remaining bacteria at his wife’s urging (apparently because bad breath is also one of the symptoms of H. pylori infection). Marshall’s self-experiment was published in the Australian Medical Journal and is among the most cited articles ever published in the journal.

    Another relatively common cause of peptic ulcers is the chronic use of non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen. Additional contributing factors may include tobacco smoking and stress, although these factors have not been demonstrated conclusively to cause peptic ulcers independent of H. pylori infection. Contrary to popular belief, diet does not appear to play a role in either causing or preventing peptic ulcers. Eating spicy foods and drinking coffee and alcohol were once thought to cause peptic ulcers. These lifestyle choices are no longer thought to have much if any effect on the development of peptic ulcers.

    Peptic ulcers are typically diagnosed on the basis of symptoms or the presence of H. pylori in the GI tract. However, endoscopy (Figure \(\PageIndex{3}\)), which allows direct visualization of the stomach and duodenum with a camera, may be required for a definitive diagnosis. Peptic ulcers are usually treated with antibiotics to kill H. pylori, along with medications to temporarily decrease stomach acid and aid in healing. Unfortunately, H. pylori have developed resistance to commonly used antibiotics, so treatment is not always effective. If a peptic ulcer has penetrated so deep into the tissues that it causes perforation of the wall of the stomach or duodenum, then emergency surgery is needed to repair the damage.

    Endoscopy training
    Figure \(\PageIndex{3}\): A doctor inserts a tiny camera through a tube (called an endoscope) to examine a patient’s upper GI tract for peptic ulcers. He views the image created by the camera on a screen above the patient’s head.


    Gastroenteritis viruses
    Figure \(\PageIndex{4}\): These micrographs show four types of viruses that commonly cause gastroenteritis in humans: A. rotavirus, B. adenovirus, C. norovirus, and D. astrovirus.

    Gastroenteritis, also known as infectious diarrhea, is an acute and usually self-limiting infection of the GI tract by pathogens. Symptoms typically include some combination of diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydration may also occur. The illness generally lasts less than two weeks, even without treatment, but in young children, it is potentially deadly. Gastroenteritis is very common, especially in poorer nations. Worldwide, up to five billion cases occur each year, resulting in about 1.4 million deaths. In the United States, infectious diarrhea is the second most common type of infection after the common cold.

    Commonly called “stomach flu,” gastroenteritis is unrelated to the influenza virus, although viruses are the most common cause of the disease (Figure \(\PageIndex{4}\)). In children, rotavirus is most often the cause, whereas norovirus is more likely to be the cause in adults. Besides viruses, other potential causes of gastroenteritis include fungi, protozoa (including Giardia lamblia, described below), and bacteria (most often Escherichia coli or Campylobacter jejuni). Transmission of pathogens may occur due to eating improperly prepared foods or foods left to stand at room temperature, drinking contaminated water, or having close contact with an infected individual.

    Gastroenteritis is less common in adults than children, partly because adults have acquired immunity after repeated exposure to the most common infectious agents. Adults also tend to have better hygiene than children. If children have frequently repeated incidents of gastroenteritis, they may suffer from malnutrition, stunted growth, and developmental delays. Many cases of gastroenteritis in children can be avoided by giving them a rotavirus vaccine. Frequent and thorough hand washing can cut down on infections caused by other pathogens.

    Treatment of gastroenteritis generally involves increasing fluid intake to replace fluids lost in vomitus or diarrhea. Oral rehydration solution, which is a combination of water, salts, and sugar, is often recommended. In severe cases, intravenous fluids may be needed. Antibiotics are not usually prescribed because they are ineffective against viruses that cause most cases of gastroenteritis.


    Giardia lamblia
    Figure \(\PageIndex{5}\): Giardia lamblia is a single-celled organism that parasitizes the GI tract of humans as well as many other animal species. It is a eukaryotic cell with tentacle-like extensions.

    Giardiasis, popularly known as beaver fever, is a type of gastroenteritis caused by a GI tract parasite, the single-celled protozoan Giardia lamblia (Figure \(\PageIndex{5}\)). The parasite inhabits the digestive tract of a wide variety of domestic and wild animal species in addition to human beings, including cows, rodents, and sheep as well as beavers (hence its popular name). Giardiasis is one of the most common parasitic infections in people the world over, with hundreds of millions of people infected worldwide each year.

    Transmission of G. lamblia is via a fecal-oral route. Those at greatest risk include travelers to countries where giardiasis is common, people who work in child-care settings, backpackers and campers who drink untreated water from lakes or rivers, and people who have close contact with infected people or animals in other settings. In the United States, giardiasis occurs more often during the summer than in other seasons, probably because people spend more time outdoors and in wild settings at that time of year.

    Symptoms of giardiasis can vary widely. About a third of people with the infection have no symptoms, whereas others have severe diarrhea with poor absorption of nutrients. Problems with absorption occur because the parasites inhibit intestinal digestive enzyme production, cause detrimental changes in microvilli lining the small intestine, and kill off small intestinal epithelial cells. The illness can result in weakness, loss of appetite, stomach cramps, vomiting, and excessive gas. Without treatment, symptoms may continue for several weeks. Treatment with an antibiotic may be needed if symptoms persist longer or are particularly severe.


    1. What is inflammatory bowel disease?
    2. Describe typical symptoms of inflammatory bowel disease.
    3. Compare and contrast Crohn’s disease and ulcerative colitis.
    4. What is diverticulosis? How is it related to diverticulitis?
    5. Identify the locations and causes of peptic ulcers.
    6. Define and describe gastroenteritis.
    7. Identify the cause of giardiasis. Why may it cause malabsorption?
    8. Which of the following does not normally affect the small intestine?

      A. Peptic ulcers

      B. Crohn's disease

      C. Giardiasis

      D. Ulcerative colitis

    9. Name three disorders of the GI tract that can be due to bacteria.
    10. True or False. A colonoscopy can be used to examine the small intestine.
    11. True or False. Peptic ulcers are mainly due to diet.
    12. Name one disorder of the GI tract that can be helped by anti-inflammatory medications and one that can be caused by chronic use of anti-inflammatory medications.
    13. People with ulcerative colitis should be frequently screened for _________ cancer.
    14. Describe one reason why it can be dangerous to drink untreated water.
    15. Do you think the “stomach flu” can be prevented by an influenza vaccine? Why or why not?


    1. BADAS Crohn by Dayavathi Ashok and Patrick Kiely, CC BY 2.0 via Wikimedia Commons
    2. Diverticula by Haymanj, a retired pathologist from Melbourne, Australia. public domain via Wikimedia Commons
    3. Endoscopy training by Yuya Tamai, CC BY 2.0 via Wikimedia Commons
    4. Gastroenteritis viruses by Graham Beards, CC BY 3.0 via Wikimedia Commons
    5. Giardia lamblia by CDC / Janice Haney Carr, public domain via Wikimedia Commons
    6. Text adapted from Human Biology by CK-12 licensed CC BY-NC 3.0

    This page titled 10.7: Disorders of the Gastrointestinal Tract is shared under a CK-12 license and was authored, remixed, and/or curated by Suzanne Wakim & Mandeep Grewal via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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