Overview of Diverticulitis
Diverticulitis often develops as a result of a combination of diet and a weakness in the anatomy. In medical terminology, a small out-pouching in the wall of a tubular structure is called a diverticulum, literally a structure that diverts whatever is flowing in the tube away from the main channel. Diverticuli (plural of "diverticulum"), sometimes called "tics" occur in the urinary bladder, other parts of the urinary tract, and throughout the gastrointestinal tract.
The best way to imagine how these out-pouches develop would be to conceive of the GI tract as a rubber tube that is subject to repeated bouts of increased pressure. This pressure comes from diet (e.g., large meals, excessive drinking).
Just like arterial aneurysms that develop from constant blood pressure at weak spots in arteries, diverticuli develop from constant pressure over weak spots in the GI tract. They may occur in the beginning of the esophagus (Zenkers diverticulum) and are often seen in the lower esophagus, the stomach, the duodenum, and throughout the small bowel. The large bowel is particularly prone. The end of the large bowel (rectosigmoid) is affected most often, although it is not uncommon for tics to occur at the beginning of the large bowel (cecum).
In most patients over the age of 40, a barium enema will show diverticuli. Often there are numerous diverticuli in the rectosigmoid portion of the large bowel. Technically, the rectosigmoid section of the large bowel includes the rectum and sigmoid, but in realty most diverticuli arise from the sigmoid and not the rectum. In the text that follows the terms sigmoid and rectosigmoid are used interchangeably. The rectosigmoid section of the large bowel is particulary prone to diverticulitis.
A barium enema demonstrates why the sigmoid may be most vulnerable to tics. The barium goes into the rectum without incidence, but once it reaches the sigmoid colon, this section becomes irritated and attempts to excrete the foreign material. Often the colon will go into spasm, contracting almost continuously in its efforts. That spasm in the sigmoid often causes discomfort or even colicky pain.
A diet high in meat and processed food and low in bulk (fiber) contributes to diverticulitis. Bowel weakness and a poor diet often results in a spastic sigmoid contracting against little bulk and numerous diverticuli.
The GI tract is not a sterile environment—in fact, many types of bacteria pass through it. Diverticuli provide a place for bacteria to grow and multiply. The walls of diverticuli are very thin and in some cases, the walls open, causing infection and inflammation—diverticulitis.
When diverticulitis develops, the degree of irritability increases sharply, with more spasm and pain. The patient may experience difficulty having bowel movements and develop fever. If allowed to progress, abscesses may develop, as well as small tracts that connect the rectosigmoid to other organs such as the urinary bladder and the vagina. These are serious complications that need aggressive treatment.