Many conditions or disorders are associated with the digestive system. These include:

• Indigestion. A mild condition marked by unpleasant abdominal sensations after eating. Symptoms of indigestion include heartburn, nausea and gas and bloating.
  
  
• Diarrhea. Repeated, loose, watery and often uncontrolled bowel movements occurring more than three times a day.
  
  
• Constipation. Inability or difficulty passing feces from the body, resulting in too few bowel movements.
  
  
• Gas in the digestive tract. Caused by swallowing air or the breakdown of certain undigested foods by bacteria in the colon, gas in the digestive tract may result in belching, flatulence, bloating and abdominal pain or discomfort.
  
  
• Gastritis. Inflammation in the stomach lining caused by either a bacterial infection or the chronic use of certain medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), which weaken its protective mucous coating.
  
  
• Peptic ulcers. Painful, bleeding sores in the lining of the stomach that occur when the protective mucous coating of these organs is weakened. Ulcers may also occur in the esophagus and part of the small intestine.
  

  

• Gastroesophageal reflux disease (GERD). A condition in which the contents of the stomach flow back (reflux) into the esophagus and damage its lining. GERD occurs when the lower esophageal sphincter, which separates the esophagus and stomach, does not close properly.
  

  

• Infections.  Many bacteria, viruses and parasites, sometimes in food or water, may invade the body through the digestive system. They may cause foodborne illnesses and infections such as gastroenteritis.
  
  
• Irritable bowel syndrome (IBS). A common disorder resulting from improper functioning of the muscles in the colon. Symptoms of IBS include abdominal cramping, bloating, constipation and diarrhea.
  
  
• Inflammatory bowel disease. Chronic inflammation of the intestines. Examples of inflammatory bowel disease include ulcerative colitis, which often affects just the rectum and the colon, and Crohn's disease, which can affect the whole alimentary canal as well as other parts of the body.
  
  
• Diverticular disease. A condition characterized by the presence of small, abnormal sacs (diverticula) in the wall of the colon, which may become infected. The sacs occur most frequently in the last section of the large intestine just above the rectum. There may be only a single sac or there may be hundreds.
  
  
• Esophagitis. Inflammation of the esophagus caused by infection or the prolonged use of certain medications, such as NSAIDs.
  
  
• Cholecystitis. A condition characterized by inflammation of the gallbladder and usually associated with gallstones.
  

  

• Hepatitis. Inflammation of the liver, which can result in its impairment.
  
  
• Appendicitis. Inflammation of the appendix, a pouch in the large intestine that has no known function. An inflamed appendix can be life-threatening if it bursts, so appendicitis is usually treated with surgical removal, or appendectomy.
  

  

• Pancreatitis. Inflammation of the pancreas, most often caused by alcohol abuse or gallstones.
  
  
• Celiac disease. A digestive disorder caused by an abnormal response of the immune system to a protein called gluten that is found in foods containing wheat, oats, rye and barley.
  
  Patients with celiac disease have difficulty digesting nutrients from the foods they eat because gluten damages the lining of the intestines over time. Symptoms of the disorder include diarrhea, bloating and stomach pain.
  
  
• Tracheoesophageal fistula. A congenital condition in which there is a gap between the upper and lower sections of the esophagus, preventing the passage of food and liquids.
  
  
• Cystic fibrosis (CF). A chronic, inherited condition characterized by the overproduction of thick, abnormal mucus, which blocks the ducts or passageways in the pancreas and prevents its digestive juices from entering the intestines. CF patients have difficulty digesting proteins and fats. As a result, important nutrients pass out of the body unused and patients are underweight.
  
  
• Lactose intolerance. An inability to break down lactose (the main sugar found in dairy products) due to the lack of lactase, a specific digestive enzyme. Patients with lactose intolerance experience symptoms such as gas, bloating and abdominal pain after consuming a food or beverage that contains lactose.
  
  
• Peritonitis. An inflammation of the abdominal cavity and its lining (peritoneum) that typically involves infection. Symptoms of peritonitis include abdominal pain and tenderness, fever and vomiting.
  
  
• Inguinal hernia. A bulging of part of the intestine that pushes into the groin through a weakness in the abdominal wall. Characterized by pain and feelings of pressure or burning in the groin, inguinal hernia often requires surgical treatment.
  
  
• Hiatal hernia. A protrusion of the stomach into the chest cavity through an opening in the diaphragm. Hiatal hernia often results in reflux.
  
  
• Hemorrhoids. A swelling and stretching of the veins in the wall of the anus and rectum. Some people with hemorrhoids experience bleeding, pain and a feeling of fullness in the rectum while others have no symptoms at all.
  
  
• Gastroparesis. A condition in which the stomach muscles function improperly, causing food and liquid to pass too slowly into the small intestine. Common symptoms include nausea, vomiting and feeling full early in a meal (early satiety).
  
  
• Barrett’s esophagus. A precancerous condition in which the cells lining the lower part of the esophagus are replaced with abnormal cells. The condition is frequently associated with GERD.