Diverticulosis is characterized by the presence of small, abnormal pouches, or diverticula, in the intestinal wall. They are usually caused by pressure that builds within the colon. Constipation appears to be a major cause of this intestinal pressure. The longer stool remains in the colon, the more pressure it places on the intestinal wall. Straining during a bowel movement increases this pressure even more. Spasms in the intestinal muscles as they try to push hardened stool through the colon further increase the pressure on the intestinal wall.

Not everyone has the same chance of developing diverticulosis. Risk factors for the condition include:

• Not eating enough fiber and drinking enough fluids. Fiber and water soften the stool and make it easier to pass, reducing pressure on the intestinal wall. When there is not enough fiber and water in the diet, the stool tends to be harder, leading to constipation. Diverticulosis occurs more often in areas where low-fiber diets are common, such as the United States, Europe and Australia. In rural areas of Africa and Asia, where diets tend to be rich in fiber, diverticulosis is rare.
  
  
• Age. Diverticulosis becomes increasingly more likely to develop as a patient gets older. The body becomes less efficient at waste removal and the elasticity and strength of the colon decrease with age, especially in the sigmoid colon.
  
  
• Heredity. There may be a genetic predisposition for diverticulosis. This means that a patient who has a family member with the disease may be more likely to develop it.
  
  
• Irritable bowel syndrome (IBS). Diverticulosis often occurs with IBS. The frequent intestinal spasms that may occur in IBS may increase the risk of developing diverticulosis.