The digestive system consists of a series of hollow organs, including the mouth, esophagus, stomach, small intestine, large intestine, rectum and anus, along with organs that contribute to the process of digestions, including the liver, gall bladder and pancreas. Malfunctions within the digestive system can cause the symptom of diarrhea, or loose, watery and frequent stools, which doctors classify as chronic when it occurs for more than four weeks, according to MedlinePlus.
Inflammatory Bowel Diseases
Diseases that cause inflammation of the lining of the small or large intestine interfere with the ability to absorb fluids, therefore resulting in chronic diarrhea. Crohn's disease, one type of inflammatory bowel disease, can affect any part of the digestive tract, although the Crohn's and Colitis Foundation reports that it most commonly causes inflammation in the lower portion of the small intestine, known as the ileum, and the upper portion of the large intestine, or the colon. Ulcerative colitis, another type of inflammatory bowel disease, causes inflammation and the formation of open sores, or ulcers, in the colon.
Crohn's disease causes inflammation in all the layers of the intestinal wall. Ulcerative colitis causes inflammation and sores on the lining of the colon. Another characteristic that sets Crohn's apart from ulcerative colitis is the presence of normal tissue in between patches of inflamed tissue. Ulcerative colitis causes continuous inflammation. Both conditions, however, cause chronic diarrhea.
Irritable Bowel Syndrome
Doctors classify irritable bowel syndrome, often called a spastic colon, as a functional disorder of the intestines. Irritable bowel syndrome, IBS, affects approximately 20 percent of the adults in the United States, according to the National Digestive Diseases Information Clearinghouse. Although the symptoms of IBS cause discomfort and distress, it does not permanently damage the intestines or lead to more serious illnesses.
IBS occurs when the walls of the large intestine spasm, contracting too hard and too fast followed by periods of slow contractions. Because the intestinal wall contractions keep partially digested contents moving through the system, these actions cause contents to move too quickly or too slowly. IBS causes episodes of chronic diarrhea, which occurs when the contents move too quickly, followed by episodes of constipation, resulting from the slow movements.
Surgery
Surgical procedures, such as small or large bowel resections, gastric bypass surgery and gastric resections, can cause chronic diarrhea. Each of these surgical procedures reduces the surface area of the digestive tract, reducing the capacity of the intestines to absorb excess fluids from the partially digested contents, as described by the Merck Manuals Online Medical Library. In addition, resection surgeries remove parts of the digestive tract which shortens the distance the digested contents must travel, therefore reducing the time the contents remain in the digestive tract. When contents move through the digestive tract too quickly, the intestines cannot absorb enough fluids, resulting in diarrhea.
