About the Colon
The colon is a 4 1/2-foot-long tube that constitutes the final portion of the intestinal tract. The food you eat is mostly digested in the stomach and small intestine. Residual material enters the colon, or large intestine, in the cecum, which lies in the right lower portion of the abdomen. From there, digested material travels up the ascending colon, across the transverse colon, and down the descending colon to the final portion, the sigmoid colon, in the lower left part of the abdomen. The intestinal contents take about 18 to 36 hours to journey through the colon; in the process, the few remaining nutrients are snatched into the bloodstream and much of the water is absorbed, resulting in solid fecal material.
Most folks who think about the colon worry about the polyps and cancers that may develop from epithelial cells. But problems can also develop in other areas. Diverticula are sac-like pouches that protrude from the normally smooth muscular layer of the colon (see Figure 2). They tend to develop where the muscles are weakest, at the places where penetrating vessels cross through the muscles. And in Western societies, the great majority of diverticula develop where the colon is narrowest, in the sigmoid.
Age is a major risk factor for diverticulosis. Diverticulosis is uncommon before age 40, but about one-third of all Americans will develop the condition by age 60, and two-thirds will have it by age 85. That makes diverticulosis one of the most common medical conditions in the United States. The principal factor is diet, especially the refinement of carbohydrates, which has deprived the typical American diet of much of its fiber content. Dietary fiber speeds the process of elimination, greatly reducing the likelihood of constipation. Dietary fiber is a mix of complex carbohydrates found in the bran of whole grains and in nuts, seeds, fruits, legumes, and vegetables, but not in any animal foods. Because humans cannot digest these complex carbohydrates, dietary fiber has little caloric value — but it has plenty of health value.
Inflammation puts the "itis" into diverticulitis, which is the most common complication of diverticular disease. The bacteria that are packed into feces by the hundreds of millions are responsible for the inflammation of diverticulitis, but doctors don't fully understand why some diverticula become infected and inflamed while many do not. A current theory holds that the wall of the diverticular sac becomes eroded by pressure, trapped fecal material, or both. If the damage is severe enough, a tiny perforation develops in the wall of the sac, allowing bacteria to infect the surrounding tissues. In most cases, the body's immune system is able to contain the infection, confining it to a small area on the outside of the colon. In other cases, though, the infection enlarges to become a larger abscess, or it extends to the entire lining of the abdomen, a critical complication called peritonitis.
Pain is the major symptom of diverticulitis. Because diverticulosis typically occurs in the sigmoid colon, the pain is usually most pronounced in the lower left part of the abdomen, but other areas may be involved. Fever is also very common with diverticulitis, sometimes accompanied by chills. If the inflamed sigmoid is up against the bladder, a man may develop enough urinary urgency, frequency, and discomfort to mimic prostatitis or a bladder infection. Other symptoms may include nausea, loss of appetite, and fatigue. Some patients have constipation, others diarrhea.
Ordinary diverticulitis is bad enough, but complications from diverticular disease can be life-threatening. The most common complications include:
Abscess formation - An abscess is a walled-off collection of bacteria and white blood cells — pus. Diverticulitis always involves bacteria and inflammation, but if the body can't confine the process to the wall of the colon immediately adjacent to the perforated diverticulum, a larger abscess forms. Patients with abscesses tend to be sicker than those with uncomplicated diverticulitis, and they have higher temperatures, more pain, and higher white blood cell counts. Treatment involves antibiotics and bowel rest, but it also requires drainage of the abscess. In many cases, specially trained interventional radiologists can accomplish that by using CT imagery to guide a thin plastic catheter through the skin into the abscess, allowing the pus to drain out. In most cases, the catheter stays in place for several days or until the drainage stops, while the patient continues to receive antibiotics and fluids. Sometimes, though, open surgery is required.
Peritonitis - Although an abscess requires aggressive treatment, it represents a partial success for the body's infection defense apparatus, since the infection is confined to a small area. If that containment fails, infection spreads to the entire lining of the abdomen. Patients are critically ill with high fever, severe abdominal pain, and often low blood pressure. Prompt surgery and powerful antibiotics are required.
Fistula formation- In diverticulitis, the infection can burrow into nearby tissues, such as another part of the intestinal tract, the urinary bladder, or the skin. This complication is less common than abscess formation and less urgent than peritonitis, but it does require both surgery and antibiotics.
Stricture formation -It's another uncommon complication that can develop from recurrent bouts of diverticulitis. In response to repeated inflammation, a portion of the colon becomes scarred and narrowed. Doctors call such narrowing a stricture, and they must call on surgeons to correct the problem so fecal material can pass through without obstruction.
Diverticular disease prevention
Diverticular disease of the colon is preventable. A high-fiber diet will sharply reduce the risk of developing diverticula — and even after the pouches form, dietary fiber will reduce the risk of diverticulitis and diverticular bleeding.
Fiber is important for bowel function and general health, but it can be hard to get used to. Many people feel bloated and gassy when they start a high-fiber diet, but if they stick with it, these side effects usually diminish within a month or so. Still, it's best to ease into a high-fiber diet. Increase your daily intake by about 5 grams per week until you reach your goal, and be sure to have plenty of fluids as well. For most people, a high-fiber cereal is the place to start, but if breakfast isn't your thing, you can have it any time during the day. Speak to your doctor for more information and before implementing major changes in your exercise habits or diet.